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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- α:
- Spectral Index (α): power by which an object's flux depends on frequency
- αCO:
- Alpha CO (αCO): ratio of CO emissions to H2
- Å:
- Angstrom (Å): unit of length 10-10 meters
- β:
- Beta (β): ratio of plasma pressure to magnetic pressure
- β decay:
- Beta Decay: radioactivity such that an electron or positron is emitted
- β Per:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- β Persei:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- χ² Test:
- ε:
- ε Ind:
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- ε Indi:
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- η Carinae:
- γ:
- ℏ:
- κ:
- Permeability (κ,k): ability of a material to allow fluids to pass through it
- Λ:
- Cosmological Constant (Λ): force counteracting the universe's inward gravitational pull
- Eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- ΛCDM:
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- μ:
- ν:
- Neutrino (ν): light, electrically neutral elementary particle
- Ω:
- Ω0:
- Öpik-Oort Cloud:
- Oort Cloud: cloud of comets and minor planets around the solar system
- π:
- Pion (π): first type of meson discovered
- ρc:
- Σ:
- τ:
- Optical Depth (τ): a measure of opaqueness of a path of light
- Timescale (t,τ): general length of time something takes
- τadvec:
- Advection: transport of something through a fluid's motion
- ϒ:
- 0FGL:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- 1 Jansky Empty Field Survey (1 Jy): survey to find optical identifications for weak radio sources
- 1 Jy:
- 1.27m Mount Stromlo Telescope:
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- 1.3mm Observation: observation frequency useful for detecting dust
- 1.5m Hale Telescope:
- 1/Vmax Method:
- 101955 Bennu: near-Earth asteroid that is the target of a planned retrieval mission
- OSIRIS-REx: planned space mission to return a sample of an asteroid
- 10199 Chariklo: largest minor planet in the outer solar system
- 1050cm:
- 10C:
- 134340 Pluto:
- Pluto: dwarf planet formerly listed as one of the nine planets
- 13MM:
- 140 Foot Telescope:
- 150 megaparsecs:
- 16 Psyche:
- Psyche: planned space mission to orbit an asteroid
- 16-Pole:
- 1947 Sunspot: largest sunspot ever recorded
- 1987A:
- SN 1987A (1987A): rare supernova in February 1987 visible by the naked eye
- 1999 RQ36:
- 101955 Bennu: near-Earth asteroid that is the target of a planned retrieval mission
- OSIRIS-REx: planned space mission to return a sample of an asteroid
- 1AGL:
- AGILE: Italian space gamma-ray observatory
- 1C:
- 1D Climate Model:
- 1D Model:
- 1E 6057-556:
- 1ES:
- HEAO-2: 1978 x-ray observatory space mission
- 1FGL:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- 1H:
- HEAO-1: 1977 x-ray observatory space mission
- 1RXS:
- ROSAT: 1990s German space x-ray telescope
- 1SWASP:
- SuperWASP (SWASP): broad Earth-based search for transiting planets
- 1SWASP J140747:
- J1407: star orbited by a companion with a ring system
- 1SWASP J140747.93-394542.86:
- J1407: star orbited by a companion with a ring system
- 2014 MU69:
- 21cm Experiment: search for redshifted 21cm hydrogen emission lines
- 21cm Line: hydrogen line useful for determining redshift
- 243 Ida:
- 25m Dwingeloo Radio Telescope:
- 26 Meter Telescope:
- 2C:
- 2D Model:
- 2dF:
- 2dF Galaxy Redshift Survey (2dFGRS): imaging survey of 300,000 objects
- 2dFGRS:
- 2E:
- HEAO-2: 1978 x-ray observatory space mission
- 2FGL:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- 2HWC:
- 2M:
- 2MASS:
- 2MASS 0720-0846:
- 2MASS 19425852-1956585:
- WASP-67b: hot jupiter discovered in 2011
- 2MASS J0445930-1516166:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- 2MASS J07200325-0846499:
- 2MASS J16264502-2423077:
- 2MASS J23062928-0502285:
- TRAPPIST-1: red dwarf with exoplanet near the habitable zone
- 2MASS Photometric System:
- 2MASX:
- 2U:
- Uhuru: 1970 satellite x-ray telescope
- 30 Doradus:
- SAGE: survey of gas and dust in the Magellanic Clouds
- 32-Pole:
- 3C:
- 3C 273: first quasar discovered
- 3C 295: distant radio galaxy
- 3C 303: Seyfert galaxy
- 3C 327: elliptical radio galaxy
- 3C 405:
- Cygnus A (3C 405,QSO B1957+405): early-discovered radio galaxy and quasar
- 3C 48: radio galaxy/quasar
- 3C 9: first quasar discovered
- 3CR:
- 3CRR:
- 3D Model:
- 3D-HST: near-infrared survey of 100,000 galaxies by HST
- 3GM:
- JUICE: mission to Jupiter in development
- 4-Metre Multi-Object Spectroscopic Telescope:
- 4MOST: planned spectrograph for VISTA telescope
- 43 Meter Telescope:
- 4C:
- 4MOST: planned spectrograph for VISTA telescope
- VISTA: 4.1 meter telescope in Paranal Observatory in Chile
- 4U:
- Uhuru: 1970 satellite x-ray telescope
- 51 Pegasi:
- 55 Cancri e (55 Cnc e): superearth orbiting a Sun-like star
- 55 Cnc e:
- 55 Cancri e (55 Cnc e): superearth orbiting a Sun-like star
- 5535 Annefrank:
- Stardust: space mission to collect comet coma dust
- 67P:
- 67P/C-G:
- 67P/Churyumov-Gerasimenko (67P,67P/C-G): comet visited by Rosetta space mission
- CAESAR: planned space mission to return a sample of a comet
- Rosetta: space probe that visited a comet
- 6dF:
- 775 AD Event: apparent solar eruption, based upon tree-ring evidence
- 87GB:
- 87GB Catalog of Radio Sources (87GB): 1980s Green Bank radio survey
- 8C:
- 951 Gaspra:
- μ:
- Permeability (κ,k): ability of a material to allow fluids to pass through it
- a:
- b:
- e:
- [CH]:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- [CI]:
- Carbon (C): element, C, atomic number 6
- Fine Structure: spectral lines due to electron spin and relativistic effects
- [CII]:
- [O III]:
- A:
- A sample of 669 ultra steep spectrum radio sources to find high redshift radio galaxies:
- USS Sources: catalog of sources with steep spectral index
- A+E Galaxy:
- A-Class:
- A-Type Star (A): type of star with about 2 times the mass of the Sun
- A-Type Star (A): type of star with about 2 times the mass of the Sun
- A0 V Star:
- A1:
- HEAO-1: 1977 x-ray observatory space mission
- A2:
- HEAO-1: 1977 x-ray observatory space mission
- A3:
- HEAO-1: 1977 x-ray observatory space mission
- A4:
- HEAO-1: 1977 x-ray observatory space mission
- A0:
- Axion (A0): proposed light, electrically neutral elementary particle
- AAO:
- AAOmega:
- AAT:
- AAVSO:
- APASS: down to 16 magnitude
- AAVSO Photometric All-Sky Survey:
- APASS: down to 16 magnitude
- AB Magnitude:
- AB System: monochromatic magnitude calibration based upon absolute values
- AB System: monochromatic magnitude calibration based upon absolute values
- abbreviation:
- HRS: high resolution spectrography
- Abell:
- Abell 1367:
- Abell 1656:
- Abell 262:
- Abell 347:
- Abell 426:
- Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
- Aberration: types of flaws in telescope images
- Abiotic Oxygen: oxygen from non-life sources
- Ablation: erosion of the surface of an object
- Absolute Astrometry:
- Astrometry: precise measurement of the position and movement of stars
- Absolute Bolometric Magnitude:
- Absolute Magnitude (M): magnitude as seen from 10 parsecs
- Absorption: removal of photons from a beam of EMR
- Absorption Band:
- Absorption Coefficient: measure of how much light a substance absorbs
- Opacity: a measure of opaqueness of a material
- Absorption Cross Section:
- Absorption Line: dark line in a spectrum
- Absorption Line Galaxy:
- Absorption Spectroscopy:
- Abundances: relative amounts of each chemical element
- Abundances Of The Chemical Elements:
- Abundances: relative amounts of each chemical element
- AC:
- AGILE: Italian space gamma-ray observatory
- ACA:
- Academia Sinica:
- Academia Sinica Institute of Astronomy and Astrophysics (ASIAA): Taiwanese astrophysics research organization
- ACAM:
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- Accretion Disk: disk around an astronomical body of material that is accreting
- Accretion Luminosity:
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- Accretion Rate: rate of addition of mass to an object
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- Autoconversion Rate: rate at which water changes from cloud droplets to new raindrops
- Accretion Runaway:
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- ACE:
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- Achernar: ninth-brightest star in the sky
- achromatic transit:
- acidity:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Carbonate System: system governing water and CO2 in the presence of each other
- ACIS:
- ACO:
- Acoustic Frequency:
- Acoustic Peak:
- ACR:
- ACRIM:
- ACS:
- ACSIS:
- ACT:
- ACT Reference Catalog:
- Hipparcos: ESA astrometry space observatory circa 1990
- ACT Survey:
- ACT-RC:
- Hipparcos: ESA astrometry space observatory circa 1990
- Active Galactic Nucleus (AGN): central region of a galaxy with extremely high luminosity
- Active Galaxy: galaxy with an active, i.e., extremely luminous central region
- ACTPol:
- ACTPol Survey:
- Actuator: telescope control motor
- AD Leo:
- AD Leonis (AD Leo): active red dwarf
- Adaptive Alignment:
- Adaptive Mesh Refinement (AMR): numerical modeling method balancing detail with tractability
- Adaptive Optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- Adaptive Refinement Tree (ART): algorithm-type for solving n-body problem
- Adaptive-Optics:
- Adaptive Optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- ADEPT:
- WFIRST: proposed space observatory
- Adiabatic Index:
- Specific Heat: Ratio of added temperature to added heat for a material
- Adiabatic Process: process that occurs with no transfer of heat
- AdLIGO:
- LIGO: pair of observatories to detect gravitational waves
- Adrastea:
- ADS:
- Adsorption: adhesion to a surface
- AdvACT:
- AdvACT Survey:
- Advanced Composition Explorer (ACE): satellite collecting solar wind and cosmic rays
- Advanced Dark Energy Physics Telescope:
- WFIRST: proposed space observatory
- Advanced LIGO:
- LIGO: pair of observatories to detect gravitational waves
- Advanced Telescope for High Energy Astrophysics:
- Advection: transport of something through a fluid's motion
- Advection Length Scale:
- Advection: transport of something through a fluid's motion
- Advection Timescale:
- Advection: transport of something through a fluid's motion
- Timescale (t,τ): general length of time something takes
- Advection Velocity Scale:
- Advection: transport of something through a fluid's motion
- Ae Star:
- Be Star: early star with Balmer emission lines
- AEGIS: survey study of distant galaxies
- Aerosols: particles suspended in an atmosphere
- AF2:
- AFTA:
- WFIRST: proposed space observatory
- AFWA:
- MarsWRF: Mars-oriented general circulation model
- AGB:
- Age Of The Universe:
- Hubble Constant (H0): rate of expansion of the universe
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- Age-Metallicity Relation:
- Age-Velocity-Metallicity Relation:
- Agena:
- AGILE: Italian space gamma-ray observatory
- AGN:
- AGN Bubble:
- AGN Feedback:
- AGN Outflow:
- AIA:
- AIM-CO: survey of CO from star forming epoch
- Air Force Weather Agency:
- MarsWRF: Mars-oriented general circulation model
- Air Mass:
- Airmass: measure of Earth-atmosphere attenuation for a telescope observation
- airborne:
- Airmass: measure of Earth-atmosphere attenuation for a telescope observation
- Airy Disc:
- Airy Disk: image pattern an optical system produces from light from a point
- Airy Disk: image pattern an optical system produces from light from a point
- Airy Pattern:
- Airy Disk: image pattern an optical system produces from light from a point
- Aitken Double Star Catalogue (ADS): 1932 catalog with multiple star systems and non-orbiting double stars
- AKARI: Japanese space infrared telescope
- Albedo: measure of reflectance
- Earthshine: reflected and electromagnetic radiation from Earth
- Alcock-Paczyński Effect: distortion of the apparent size of galaxy clusters
- Alcock-Paczyński Test:
- ALESS:
- ALFA:
- ALFALFA: HI survey of many galaxies
- Alfvén Mach Number:
- Alfvén Wave: a type of transverse wave along magnetic field lines in plasma
- Mach Number: ratio of a flow with the speed of sound
- Alfvén Radius:
- Neutron Star: stellar remnant consisting entirely of solar masses of neutrons
- Alfvén Speed:
- Alfvén Wave: a type of transverse wave along magnetic field lines in plasma
- Alfvén Velocity:
- Alfvén Wave: a type of transverse wave along magnetic field lines in plasma
- Alfvén Wave: a type of transverse wave along magnetic field lines in plasma
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Algol Paradox:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Algol Variable:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Algols:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- algorithm:
- Adaptive Refinement Tree (ART): algorithm-type for solving n-body problem
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- ALICE:
- Alkane:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Alkene:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Alkyne:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- All Sky:
- All Sky Automated Survey (ASAS): Polish survey of 20,000 objects brighter than 14 magnitude
- All Sky Automated Survey for SuperNovae (ASAS-SN,ASASSN): survey of both hemispheres for supernovae
- All Sky Surveys:
- Survey Field: portion of the celestial sphere where a survey's observations aim
- All-Wavelength Extended Groth Strip International Survey:
- AEGIS: survey study of distant galaxies
- Allen Telescope Array (ATA): array of radio telescopes in northern California for SETI
- ALMA:
- ALMA Protostellar Interferometric Line Survey:
- ALMA Spectroscopic Survey in the Hubble UDF:
- ASPECS: millimeter survey of HUDF
- ALMA-LESS:
- ALMA-PILS Survey: millimeter survey of a protostar
- ALMA-T:
- Alnilam:
- Orion: well-known constellation in the northern hemisphere
- Alpha Canis Majoris:
- Sirius: brightest star in the sky
- Alpha Capture: combination of a nucleus and an incoming alpha particle
- Alpha Centauri: nearest star system
- Starshot: plan for mission to fly by Alpha Centauri
- Alpha CO (αCO): ratio of CO emissions to H2
- Alpha Cygni Variable Star:
- Rigel: brightest star in constellation Orion
- Alpha Element: element created by alpha capture
- Alpha Eridani:
- Achernar: ninth-brightest star in the sky
- Alpha Ladder:
- Alpha Lyrae:
- Vega: brightest star in constellation Lyra
- Alpha Orionis:
- Betelgeuse: second brightest star in constellation Orion
- Alpha Particle: essentially a helium nucleus stemming from radioactivity
- Alpha Process: synthesization of elements through alpha capture
- Alpha Ray:
- Alpha Species:
- Alt-Azimuth Mount:
- Alt/Az system:
- Altazimuth Mount: simple two-axis telescope mount
- altazimuth system:
- Altazimuth Telescope:
- Altitude:
- Altitude-Azimuth:
- Aluminum:
- CAI: calcium/aluminum specs in chondrites
- Globular Cluster (GC): spherical group of stars orbiting a galaxy
- AM:
- AM Herculis Star:
- amateur:
- Astrolux: historically popular amateur telescope
- AMBER:
- American Association of Variable Star Observers:
- APASS: down to 16 magnitude
- Amine: type of compound containing nitrogen
- Amino Acid:
- Amine: type of compound containing nitrogen
- Glycine (Gly,G): smallest of the twenty common amino acids
- Lego Principle: principle that life is associated with a skew in molecule abundances
- Ammonia (NH3): compound of nitrogen and hydrogen
- Amorphous:
- Ice: solid state of water
- Amorphous Galaxy:
- Ampere's Law:
- AMR:
- amu:
- Analog Computer:
- analysis:
- Analyte:
- Titration: analyzing a chemical solution by color change
- Analytical Method:
- Analytically:
- ancient:
- Hipparchus: Greek astronomer who developed concept of magnitude
- And:
- Andromeda (M31): spiral galaxy in the Local Group
- And I:
- Andromeda (M31): spiral galaxy in the Local Group
- Andromeda (M31): spiral galaxy in the Local Group
- Andromeda I:
- Andromeda (M31): spiral galaxy in the Local Group
- Andromeda II:
- Andromeda (M31): spiral galaxy in the Local Group
- Angle Of Incidence:
- Angle Of Refraction:
- Anglo-Australian Telescope (AAT): 3.9m reflector telescope in Australia
- Angstrom (Å): unit of length 10-10 meters
- Angular Area:
- Field of View (FOV): angular measure of how much an optical instrument can view
- Solid Angle (Ω): two-dimensional analog of an angle
- Angular Diameter Distance:
- Angular Differential Imaging:
- Angular Magnification: a magnification measure for a magnifier with an eyepiece
- Angular Momentum:
- Angular Power Spectrum: method of characterizing the CMB
- Angular Resolution: measure of a telescope's ability to distinguish spatial detail
- Angular Size-redshift Relation:
- Angular Velocity:
- Anisotropy: directional dependence such as temperature variation in the CMB
- Anlitak:
- Orion: well-known constellation in the northern hemisphere
- Annihilation:
- Antimatter: similar to normal matter but with opposite electrical charge
- Anomalous Cosmic Rays (ACR): cosmic rays with unexpectedly low energies
- Antenna Noise Temperature:
- Antenna Pattern: a radio telescope's pattern of directional sensitivity
- Antenna Temperature: parameter in determining noise introduced by an antenna
- Antielectron:
- Antimatter: similar to normal matter but with opposite electrical charge
- Antihydrogen:
- Antimatter: similar to normal matter but with opposite electrical charge
- Antimatter: similar to normal matter but with opposite electrical charge
- Antineutrino:
- Antimatter: similar to normal matter but with opposite electrical charge
- Antineutron:
- Antimatter: similar to normal matter but with opposite electrical charge
- Antiproton:
- Antimatter: similar to normal matter but with opposite electrical charge
- Antiquark:
- Antimatter: similar to normal matter but with opposite electrical charge
- Particle: very small thing
- Antu Telescope:
- AO:
- Ap Star: peculiar type of A star
- Apache Point Observatory:
- apapsis:
- Apsis: closest or furthest point in an eccentric orbit
- APASS: down to 16 magnitude
- Apertif:
- Aperture: opening through which light passes
- Aperture Array:
- Phased Array: method of using a set of antennas directionally
- Aperture Photometry: method of determining the brightness of an imaged star
- Aperture Synthesis: interferometry to simulate a larger aperture telescope
- APEX:
- APG:
- Aphelion:
- Apsis: closest or furthest point in an eccentric orbit
- Astronomical Unit (AU): about 93 million miles
- Oort Cloud: cloud of comets and minor planets around the solar system
- APM:
- APM Galaxy Survey (APMUKS): 1990s survey of galaxies in southern sky
- APMUKS:
- APO:
- APO Galactic Evolution Experiment:
- apoapse:
- Apsis: closest or furthest point in an eccentric orbit
- apoapsis:
- Apsis: closest or furthest point in an eccentric orbit
- Eccentricity (e): degree to which an orbit is non-circular
- apocenter:
- Apsis: closest or furthest point in an eccentric orbit
- Apodization: improving telescope images by manipulating diffraction
- Apodize:
- Apodization: improving telescope images by manipulating diffraction
- apogalacticon:
- Apsis: closest or furthest point in an eccentric orbit
- APOGEE:
- APOGEE Spectrograph:
- APOGEE-2:
- Apparent Binary:
- Apparent Magnitude (m): magnitude as seen from Earth adjusted for atmosphere
- Apparent Radiant:
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Apsis: closest or furthest point in an eccentric orbit
- Aqueous Solution:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Arakelian Catalog (Ark): 1970s list of small/bright galaxies
- ARC 3.5m:
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- archive:
- HEASARC: archive of NASA data on high energy astronomy
- MAST: archive of data from surveys and missions
- ARCoRISI:
- Arcturus: fourth brightest star in the sky
- Arecibo:
- Arecibo L-band Feed Array:
- Arecibo Observatory (NAIC): large 305m radio telescope in Puerto Rico
- Arecibo Occultation Survey (AO): 1960s radio survey using occultations by the moon
- Arene:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- AREPO: cosmology simulation using moving mesh technique
- ARGOS:
- Argument Of Periapsis:
- Apsis: closest or furthest point in an eccentric orbit
- Orbital Element: parameters describing an orbit
- argument of pericenter:
- Apsis: closest or furthest point in an eccentric orbit
- argument of perifocus:
- Apsis: closest or furthest point in an eccentric orbit
- Argus:
- Ariel:
- ARIEL: planned space mission for exoplanet spectrography
- Moon: Earth's natural satellite
- Uranus: second outer-most solar system planet
- ARIES:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Arizona:
- Arizona Radio Observatory:
- Ark:
- Aromatic Hydrocarbon:
- Arp Atlas of Peculiar Galaxies:
- Arp Catalog of Peculiar Galaxies:
- Arp-Madore Catalog of Southern Peculiar Galaxies (AM): 1970s-1980s catalog from the UK Schmidt Survey
- array:
- arrays:
- Phased Array: method of using a set of antennas directionally
- ART:
- Artificial Satellite:
- Moon: Earth's natural satellite
- ASAS:
- ASAS-SN:
- ASASSN:
- Ascending Node:
- ASI:
- AGILE: Italian space gamma-ray observatory
- Cassini: explorer spaceship sent to Saturn
- ASIAA:
- ASIAA Intensity Mapping for CO:
- AIM-CO: survey of CO from star forming epoch
- Asiago Observatory:
- Asiago Supernova Catalog (B/SN): 1999 catalog of known supernovae and their galaxies
- ASKAP:
- ASM:
- RXTE: space mission to time X-ray variations
- ASPECS: millimeter survey of HUDF
- ASPERA:
- Association of Universities for Research in Astronomy (AURA): group of universities operating a number of observatories
- ASTE:
- Asteroid: minor planet without comet characteristics
- 101955 Bennu: near-Earth asteroid that is the target of a planned retrieval mission
- Asteroid Belt: disk of orbiting planetoids/asteroids
- Asteroid: minor planet without comet characteristics
- Planetoid: an asteroid or physically similar body
- Asteroid Family: set of asteroids based on similar orbits
- asteroids:
- Asteroid Belt: disk of orbiting planetoids/asteroids
- Asteroid Family: set of asteroids based on similar orbits
- Kirkwood Gap: gaps in asteroid orbital radii corresponding to Jupiter resonances
- OSIRIS-REx: planned space mission to return a sample of an asteroid
- Psyche: planned space mission to orbit an asteroid
- Asteroseismology: study of stars through analysis of their pulsation
- Astro:
- Gaia: survey satellite at 400-1000 nanometers
- Astro-1:
- Astro-2:
- ASTRO-A:
- ASTRO-B:
- ASTRO-C:
- ASTRO-D:
- ASTRO-EII:
- ASTRO-F:
- AKARI: Japanese space infrared telescope
- ASTRO-H: Japanese space x-ray telescope
- Astro-Rivelatore Gamma a Immagini Leggero:
- AGILE: Italian space gamma-ray observatory
- AstroBEAR: MHD simulation system
- Astrobiology: study of extra-terrestrial life
- Astrocats: software to create and manage an astronomy catalog
- Astrographic Catalog / Tycho:
- Hipparcos: ESA astrometry space observatory circa 1990
- Astrolux: historically popular amateur telescope
- Astrometric Binary: binary star system detected by observing the movement of a star
- Astrometry: precise measurement of the position and movement of stars
- Astrometric Binary: binary star system detected by observing the movement of a star
- Gaia: survey satellite at 400-1000 nanometers
- Hipparcos: ESA astrometry space observatory circa 1990
- NOMAD: astrometric star catalog
- Proper Motion: apparent motion in relation to the position of the Sun
- USNO: observatory obtaining astronomical data for Naval use
- VERA: VLBI project to map the Milky Way
- ASTRON: Netherlands radio astronomy research organization
- Astronet: European astronomy consortium
- astronomer:
- Hipparchus: Greek astronomer who developed concept of magnitude
- Astronomical Catalog: lists of observed astronomical bodies and their characteristics
- Astronomical Quantities: some astronomy amounts/numbers
- Astronomical Survey: project to collect uniform astronomical data across the sky
- Astronomical Unit (AU): about 93 million miles
- astronomy:
- astrophysics:
- Astrophysics Focused Telescope Assets:
- WFIRST: proposed space observatory
- Asymptotic Giant Branch (AGB): a second stage of helium burning in some stars
- ATA:
- ATA-350:
- ATA-42:
- Atacama Compact Array:
- Atacama Cosmology Telescope (ACT): 6 meter microwave survey telescope in Chile
- Atacama Desert: high altitude, dry plateau in Chile, the site of observatories
- Atacama Large Millimeter Array (ALMA): large radio telescope array in Chile
- Atacama Pathfinder Experiment (APEX): 12-meter submillimeter telescope in Chile
- Atacama Submillimeter Telescope Experiment (ASTE): ten meter submillimeter telescope in Chile
- ATCA:
- Athena: MHD code
- ATLAS:
- Atlas 3d: survey of local galaxies
- ATLAS Code:
- Atlas of Galactic Nebulae (GN): 1980s catalog of Milky Way nebulae
- Atlas of Peculiar Galaxies (APG): 1960s catalog-book with photos
- ATLAS Stellar Model: computer model of a stellar photosphere
- ATLAS3D:
- ATLAS3D:
- ATM: unit of pressure
- Atmosphere: gas surrounding astronomical object
- Atmosphere Formation: capture and modification of a planet's gases
- Atmospheric Extinction:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Atmospheric Model: model to describe or simulate a planet's atmosphere
- Atmospheric Remote-sensing Infrared Exoplanet Large-survey:
- ARIEL: planned space mission for exoplanet spectrography
- Atmospheric Retention:
- Atmospheric Retrieval:
- Retrieval: determining measures through observation and modeling
- Atmospheric Scale Height:
- Atmospheric Temperature Profile: the atmosphere's temperature by altitude
- Atmospheric Tide: tide-type movement in the atmosphere
- Atmospheric Transparency:
- Atmospheric Window: frequency bands in which the atmosphere passes electromagnetic radiation
- Atmospheric Window: frequency bands in which the atmosphere passes electromagnetic radiation
- Atomic Excitation: atoms with electrons above the ground state
- Atomic Mass:
- Dalton (Da,u): mass unit used on atomic scale
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- Atomic Mass Unit:
- Atomic Number:
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- Isotope: subclass of an element with a specific number of nucleons
- Radioactive Decay: changes in atomic nuclei that happen over time
- Atomic Orbital:
- atoms:
- Attenuation Coefficient:
- AU:
- AURA:
- Aurora: light produced by atmosphere and solar wind
- Australia:
- Australia Telescope Compact Array (ATCA): radio telescope in eastern Australia
- Australian Astronomical Observatory:
- Australian National University 40-Inch Telescope:
- Australian Square Kilometre Array Pathfinder (ASKAP): radio telescope array of 36 12m dishes
- Autoconversion Rate: rate at which water changes from cloud droplets to new raindrops
- automated:
- APASS: down to 16 magnitude
- HATNet: distributed array of telescopes to search for transients
- KELT: pair of telescopes to search for transients
- MASCARA: distributed array of telescopes to search for exoplanets
- MEarth Project (MEarth): automated observatory for spotting changes in light from red dwarf stars
- NGTS: survey of transits from Chile
- Palomar 48 Inch Telescope (P48): 48 inch telescope at Palomar Observatory
- Palomar 60 Inch Telescope (P60): 60 inch telescope at Palomar Observatory
- Palomar Transient Factory (PTF): survey designed to find transients
- Pi Of The Sky: survey aimed at finding gamma-ray-burst visual counterparts
- Qatar Exoplanet Survey (QES): photometric survey in search of transients
- RAPTOR: automated array of telescopes to uncover and track transients
- ROTSE: automated array of telescopes to uncover and track transients
- SkyMapper: automated 1.35m optical telescope in Australia
- SPECULOOS: search for earth-like exoplanets orbiting nearby dim stars
- Trans-Atlantic Exoplanet Survey (TrES): exoplanet-search survey using three telescopes
- TRAPPIST: ground-based automatic transiting planet finding telescope
- Automatic Plate Measuring Machine:
- Autumnal Equinox:
- Equinox: times when tilt of Earth is neither toward or away from the Sun
- Avogadro Constant:
- Axial Precession:
- Precession: periodic change in a body's rotation or orbit
- Axial Tilt:
- Obliquity: angle between an object's rotational and orbital axes
- axiom:
- Axion (A0): proposed light, electrically neutral elementary particle
- Axisymmetric: identical in any direction from an axis
- Axisymmetric Galaxy:
- Galaxy: gravitationally-bound group of stars
- az/el system:
- Azane:
- Ammonia (NH3): compound of nitrogen and hydrogen
- Azimuth:
- Azimuth-Elevation:
- Azimuthal Quantum Number:
- AzTEC:
- AzTEC-3: very distant starburst galaxy
- AzV:
- B: photometric filter for blue light
- B Field:
- B(e) Star:
- Be Star: early star with Balmer emission lines
- B-Band:
- B-E Statistics:
- B-mode:
- POLARBEAR: instrument to map CMB polarization
- Polarization Modes: electric and magnetic aspects of the polarization of electromagnetic radiation
- B-Type Star (B): type of star with about 10 times the mass of the Sun
- B-V:
- Color Index: a number that characterizes the color of an object
- B/SN:
- B1900.0 Epoch:
- Epoch: time on which to base celestial coordinates
- B1950.0 Epoch:
- Epoch: time on which to base celestial coordinates
- B1957+20:
- Black Widow Pulsar (B1957+20, PSR J1959+2048, PSR B1957+20): binary system consisting of a pulsar and small companion
- B2:
- B3:
- Baade Telescope:
- Baade's Window: region of sky allowing observation into the galactic center
- Back End Instrument: instruments of a telescope that process or combine signals
- background:
- Background Imaging of Cosmic Extragalactic Polarization:
- BICEP2: surveys to measure the polarization of the CMB
- Backward Model:
- Forward Model: model producing potential observable values from parameters
- Badgerys Creek 101MHz Interferometer:
- Badgerys Creek Interferometer 101MHz Survey (Mills): early 1950s survey of southern-hemisphere radio sources
- Balbus-Hawley Instability:
- Balloon-borne Large Aperture Submillimeter Telescope:
- BLAST: balloon-borne 1.8m submillimeter telescope
- Balmer:
- Balmer Series: hydrogen lines for electrons settling from n > 2 to n = 2
- Balmer Discontinuity:
- Balmer Jump: abrupt change in stellar spectrum at end of Balmer series
- Balmer Jump: abrupt change in stellar spectrum at end of Balmer series
- Balmer Limit:
- Balmer Series: hydrogen lines for electrons settling from n > 2 to n = 2
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- Balmer's Constant:
- Balmer Series: hydrogen lines for electrons settling from n > 2 to n = 2
- Balmer-Break Galaxy (BBG): a galaxy emitting very little shorter than 3646 angstroms
- Band:
- B: photometric filter for blue light
- Extreme Ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10nm-124nm
- Extremely Low Frequency (ELF): electromagnetic radiation, frequency 3Hz to 30Hz
- Far Infrared (FIR): infrared radiation with wavelengths in the 30-450um range
- G Band: band of visible light around 5100 angstroms
- Gamma Rays: electromagnetic radiation, wavelength 10 picometers and less
- I Band: photometric filter for near infrared light
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- K Band: infrared passband centered around 2.2 microns, or 136 THz
- Microwave: electromagnetic radiation, frequency 300MHz to 300GHz
- Mid Infrared (MIR): infrared radiation with wavelengths in the 7.5um-25um range
- Near Infrared (NIR,Near-IR): electromagnetic radiation in the range of 800-2500 nm
- OIR: a spectral "band name" for both visible light and infrared
- Passband: range of electromagnetic wavelengths that a filter allows
- R Band: band of visible light around 6500 angstroms
- Radio: electromagnetic radiation, frequency 3kHz to 300GHz
- Spectral Band: set of related, closely-packed spectral lines
- Subradio: electromagnetic radiation, frequency below 3kHz
- Super Low Frequency (SLF): electromagnetic radiation, frequency 30Hz to 300Hz
- Tremendously Low Frequency (TLF): electromagnetic radiation, frequency below 3Hz
- U: photometric filter for ultraviolet light
- Ultra Low Frequency (ULF): electromagnetic radiation, frequency 300Hz to 3kHz
- Ultra-High-Energy Gamma Rays (UHEGR): energetic gamma rays with more than 100 TeV photon energy
- Ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- V: photometric filter for visible light
- Very Low Frequency (VLF): electromagnetic radiation, frequency 3kHz to 30kHz
- Very-High-Energy Gamma Rays (VHEGR): energetic gamma rays with 100 GeV to 100 TeV photon energy
- Visible Light: electromagnetic radiation, wavelength 390-750 nm
- X-ray: electromagnetic radiation, wavelength .01 to 10 nanometers
- XEUV: electromagnetic radiation in the range of .15nm-400nm
- Band Absorption:
- Band Shifting: effect of redshift on photometry
- Bandpass Filter:
- Filter: optical device to filter out part of the EMR spectrum
- Bandwidth: number of Hertz between minimum and maximum frequencies
- BAO:
- BAO Standard Ruler:
- Bar: feature of some spiral galaxies
- Barium Star:
- Barnard:
- Barnard Catalog (Barnard,B): 1919 catalog of dark nebulae
- Barnard Object:
- Barnard's Star: nearby red dwarf
- Baroclinic Atmosphere:
- Baroclinicity: measure of misalignment of fluid density and pressure
- Baroclinic Instability:
- Baroclinicity: measure of misalignment of fluid density and pressure
- Baroclinicity: measure of misalignment of fluid density and pressure
- Barotropic Atmosphere:
- Baroclinicity: measure of misalignment of fluid density and pressure
- Barred:
- Bar: feature of some spiral galaxies
- Spiral Galaxy: flat galaxy with spiraling arms
- Barred Galaxy:
- Barred Spiral Galaxy:
- Bar: feature of some spiral galaxies
- barrier:
- Barrier Penetration:
- barriers:
- Barycenter: center of mass of two orbiting bodies
- Barycentric:
- Barycentric Coordinates:
- Barycentric Julian Day BJD:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Baryon: protons, neutrons, and other three-quark particles
- Baryon Acoustic Oscillations (BAO): density fluctuations stemming from acoustic waves in the early universe
- Baryon Oscillation Spectroscopic Survey (BOSS): survey of spatial distribution of luminous red galaxies and quasars
- Baryonic Gas Fraction:
- Gas Fraction: fraction of a galaxy or cluster consisting of gas
- Baryonic Mass Density:
- Baryonic Matter:
- Baryon: protons, neutrons, and other three-quark particles
- Baryonic Tully-Fisher Relation:
- Bas:
- Basalt: an igneous rock type that shows rapid cooling
- Basel:
- Basel Astronomical Institute:
- Basel Open Cluster Catalog (Basel): list of open clusters
- Baseline:
- Parallax: angle due to different lines of sight
- Basicity:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Basis Function: one of a set of functions used to approximate a function of interest
- BAT:
- Swift: satellite for studying gamma-ray bursts
- Bathymetry: study and measurement of sea depths
- BATSE:
- Bayer Designation: star designation system dating from 1600s
- Bayes' Law:
- Bayes' Rule:
- Bayes' Theorem:
- Bayesian Probabilities:
- Bayesian Statistics: statistics method assigning probability to your belief
- BB:
- Black Body (BB): idealized object that reflects no light
- BBFS:
- HEAO-2: 1978 x-ray observatory space mission
- BBG:
- BBH:
- BCG:
- Bcool: project studying stellar magnetism
- BCS:
- Yohkoh: 1990s Japanese solar observatory spacecraft
- BD:
- BD+36 2147:
- BDF: field used in search for distant galaxies
- Be:
- Be Star: early star with Balmer emission lines
- Beagle 2:
- BearCLAW:
- Becker, White, and Edwards Catalog (BWE): 1990s radio catalog from a 91m Green Bank Telescope survey
- BEFS:
- Bell Curve:
- Bellatrix:
- Orion: well-known constellation in the northern hemisphere
- Belt:
- Zone: apparent "horizontal" band in an atmosphere
- Bennu:
- 101955 Bennu: near-Earth asteroid that is the target of a planned retrieval mission
- Benzene:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- BepiColombo: mission to Mercury
- Mercury: inner-most and smallest planet in the solar system
- Berkeley:
- Berkeley Extreme and Far-UV Spectrometer (BEFS): 1990s UV spectrometer used on two shuttle missions
- Berkeley Open Cluster Catalogue (Be): list of open clusters
- Bernard Catalogue of 349 Dark Objects in the Sky:
- Bernard Lyot Telescope:
- Beryllium:
- Besselian Date:
- Epoch: time on which to base celestial coordinates
- Beta (β): ratio of plasma pressure to magnetic pressure
- Beta Centauri: second brightest star in Centaurus
- Beta Decay: radioactivity such that an electron or positron is emitted
- Beta Drift: tendency for a cyclone to drift poleward and westward
- Beta Orionis:
- Rigel: brightest star in constellation Orion
- Beta Particle:
- Alpha Particle: essentially a helium nucleus stemming from radioactivity
- Beta Decay: radioactivity such that an electron or positron is emitted
- Lithium (Li): metal, Li, atomic number 3
- Beta Per:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Beta Persei:
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Beta Plane:
- Beta Ray:
- Beta-decay stable isobars:
- Betelgeuse: second brightest star in constellation Orion
- Orion: well-known constellation in the northern hemisphere
- Bethe:
- Foe: unit of energy on the order of a supernova's output
- BG4:
- BlackGEM: telescope array in development to follow up gravitational wave signals
- BH:
- Black Hole (BH): region of such high mass that light cannot escape
- BHB:
- bias:
- Bicarbonate:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Carbonate System: system governing water and CO2 in the presence of each other
- BICEP:
- BICEP2: surveys to measure the polarization of the CMB
- BICEP2: surveys to measure the polarization of the CMB
- Big Bang: theoretical event when the universe expanded from a point
- Black Hole (BH): region of such high mass that light cannot escape
- Cosmology: study of the life of the universe
- Dark Age: interval when the universe's hydrogen atoms were neutral
- Epoch of Reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- Lithium (Li): metal, Li, atomic number 3
- Nucleosynthesis: creation of atomic nuclei
- Recombination: time when the universe's ionized hydrogen atoms neutralized
- Big Bang Nucleosynthesis:
- Big Bang Theory:
- Big Bang: theoretical event when the universe expanded from a point
- Big Ear:
- BigBOSS: BOSS survey follow-on
- Binary Asteroid:
- Binary Black Hole:
- Binary Minor Planet (BMP): minor planet with another body orbiting it
- Binary Population Synthesis:
- Binary Star: system of two stars co-orbiting
- Achernar: ninth-brightest star in the sky
- Algol (Beta Per,β Per): multiple star system demonstrating affects of mass transfer
- Alpha Centauri: nearest star system
- Beta Centauri: second brightest star in Centaurus
- Black Widow Pulsar (B1957+20, PSR J1959+2048, PSR B1957+20): binary system consisting of a pulsar and small companion
- DQ Tau: young binary star system
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- GG Tau: much-studied quadruple star system
- Hulse-Taylor Binary (PSR B1913+16,PSR J1915+1606, PSR 1913+16): binary system consisting of a pulsar and neutron star
- Luhman 16: nearby binary brown dwarf
- Luyten 726-8: nearby binary star system
- Procyon: brightest star in Canis Minor
- Rigel: brightest star in constellation Orion
- Scholz's Star: nearby binary star with red dwarf and brown dwarf
- Sirius: brightest star in the sky
- T Tauri: variable star taken as example of young star
- binary star type:
- Binary Stars:
- Binary TNO:
- Binary Trans-Neptune Object:
- Binary X-ray Pulsar:
- Pulsar (PSR): astronomical body whose electromagnetic radiation displays a cycle
- Binary X-ray System:
- Binary YORP:
- Binding Energy: energy needed to separate two objects
- Binomial Coefficients:
- Biofluorescence: common fluorescence in organisms to dissipate harmful UV radiation
- biology:
- Biomarker:
- Biosignature: sign of life
- Bipolar Outflow: streams of matter from the poles of a protostar
- Birkhoff's Theorem: shows GR qualities of a spherically-symmetric mass
- BL Lac Object:
- Blazar: very compact variable quasar
- BL Lacertae:
- Blazar: very compact variable quasar
- Black Body (BB): idealized object that reflects no light
- Black Body Temperature:
- Black Dwarf:
- White Dwarf: stellar remnant of mostly electron-degenerate matter
- Black Hole (BH): region of such high mass that light cannot escape
- Black Hole Accretion Rate:
- Black Hole Binary (BHB,BBH): two black holes co-orbiting
- black holes:
- Black Widow Pulsar (B1957+20, PSR J1959+2048, PSR B1957+20): binary system consisting of a pulsar and small companion
- Black-Body Radiation: continuous spectrum characteristic of the temperature of a body
- Black-Body Spectrum:
- Black Body (BB): idealized object that reflects no light
- Black-Body Radiation: continuous spectrum characteristic of the temperature of a body
- Power Law: relationship with one quantity a power of another
- Blackbody:
- Black Body (BB): idealized object that reflects no light
- BlackGEM: telescope array in development to follow up gravitational wave signals
- Blanco 4m:
- Blandford-Znajek Mechanism: extraction of black-hole rotational energy by magnetized accretion disk
- Blandford-Znajek Process:
- Blanketing Effect:
- Line Blanketing: so many bunched spectral lines that they cannot be distinguished
- BLAST: balloon-borne 1.8m submillimeter telescope
- Blazar: very compact variable quasar
- Blaze Angle:
- Blazed Grating:
- Blend Analysis:
- Blended Spectra: an observed spectrum comprising light from multiple objects
- Blendanal:
- Blended Spectra: an observed spectrum comprising light from multiple objects
- Blended Spectra: an observed spectrum comprising light from multiple objects
- Blender:
- Blended Spectra: an observed spectrum comprising light from multiple objects
- Blind Survey: survey conducted independently of prior information
- blue:
- B: photometric filter for blue light
- Blue Compact Dwarf Galaxy:
- Blue Dropout Galaxy:
- Dropout: means of identifying distant galaxies
- Blue Galaxy:
- Galaxy: gravitationally-bound group of stars
- Blue Noise:
- Red Noise: noise tending toward lower frequencies
- Blue Shift:
- Line Broadening: processes causing a spectral line to have width
- Redshift (z): change to longer wavelengths due to Doppler affects
- Blue Straggler:
- Open Cluster: group of stars within a galaxy apparently formed by a single cloud
- Turn-off Point (TO): point in H-R diagram of a cluster where stars turn red
- BMBF:
- BMP:
- Bohr Model: has electrons circling nucleus in quantized orbits
- Bohr Model Of The Atom:
- Bohr Model: has electrons circling nucleus in quantized orbits
- Bohr Radius:
- Bohr Model: has electrons circling nucleus in quantized orbits
- Boil Off:
- Boiling Point:
- Bok Globule: dense molecular cloud
- Bologna Sky Survey:
- Bologna Survey:
- Bologna Survey of Radio Sources: 1970s-1980s radio survey
- Bolometer: instrument measuring heat produced by radiation
- GISMO: 2 mm bolometer camera on IRAM 30m telescope
- MUSTANG: bolometer array on the Green Bank Telescope
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- Bolometric:
- Bolometer: instrument measuring heat produced by radiation
- Bolometric Correction: difference between an object's bolometric and visible magnitudes
- Bolometric Luminosity: total luminosity of an object at all wavelengths
- Bolometric Magnitude (Mbol,Mbol): absolute magnitude of all wavelengths
- Bolshoi Simulation: cosmological simulation
- Boltzmann Constant (k): relates particle energy with temperature
- Boltzmann Distribution:
- Boltzmann Equation: equation relating atomic excitation to temperature
- Boltzmann Factor:
- Boltzmann Relation:
- Bond:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Bondi Accretion:
- Bondi Radius: radius in which a body moving through a medium will draw it in
- Bondi Radius: radius in which a body moving through a medium will draw it in
- Bone:
- Filament: linear volume of high molecular gas density within a galaxy
- Bonner Durchmusterung Catalog (BD): well-known astrometric catalog from late 1800s
- Born-Again Star:
- Bose-Einstein Distribution:
- Bose-Einstein Statistics: possible distribution of particles not bound by Pauli exclusion
- Boson:
- BOSS:
- BOSS Spectrograph:
- Bottom:
- Bouncing Barrier:
- Bound GMC:
- Bound-Bound:
- Bound-Free:
- Boundary Condition:
- Bow Shock: shock wave of a magnetosphere through the surrounding medium
- Boyle's Law:
- Bp Star:
- BP/RP:
- Gaia: survey satellite at 400-1000 nanometers
- BPS:
- Bracket Notation:
- Brackett:
- Brackett Series: hydrogen lines for electrons settling from n > 4 to n = 4
- Breaking a Degeneracy:
- Degeneracy: general word meaning a violation of normal rules
- Breaking Atmospheric Wave:
- Breaking Radiation:
- Bremsstrahlung: photon emission when a charged particle is decelerated
- Breakthrough Starshot:
- Starshot: plan for mission to fly by Alpha Centauri
- Bremsstrahlung: photon emission when a charged particle is decelerated
- Bright Giant:
- bright star:
- Achernar: ninth-brightest star in the sky
- Alpha Centauri: nearest star system
- Arcturus: fourth brightest star in the sky
- Beta Centauri: second brightest star in Centaurus
- Betelgeuse: second brightest star in constellation Orion
- Canopus: second brightest star in the sky
- Epsilon Eridani: third nearest visible star system in sky
- Procyon: brightest star in Canis Minor
- Rigel: brightest star in constellation Orion
- Sirius: brightest star in the sky
- Vega: brightest star in constellation Lyra
- Bright Star Catalog (HR,BS,YBS): early 20th century catalog of 9000 stars
- Bright Supergiant:
- Brightest Cluster Galaxy (BCG): a cluster's most luminous galaxy
- Brightest Star:
- brightness:
- British Columbia:
- Broad Band Photometry:
- Photometry: studying starlight through bandpass filters
- Broadband:
- Bandwidth: number of Hertz between minimum and maximum frequencies
- Broadening:
- Brown Dwarf (BD): star-like object with less mass than a star
- brown dwarfs:
- Brown Noise:
- Red Noise: noise tending toward lower frequencies
- Brownian Motion:
- Red Noise: noise tending toward lower frequencies
- Brownian Noise:
- Red Noise: noise tending toward lower frequencies
- Brunt-Väisälä Frequency: natural frequency of buoyancy waves
- Brute Force:
- BS:
- BSE:
- BT-Settl: model atmosphere of small stars and brown dwarfs
- BTA-6:
- BTFR:
- Bulge: denser group of stars within a larger group
- Bulk Atmosphere:
- Bulk Density: total mass divided by total volume
- Bulk Metallicity:
- Bulk Modulus:
- Sound Speed: speed at which compression waves traverse a gas
- Bulk Planetary Atmosphere:
- Bulk Silicate Earth (BSE): the early overall composition of the silicate part of Earth
- Bullet Cluster: example of two galaxy clusters in collision
- Buoyancy Frequency:
- BWE:
- BY Draconis Star:
- BY Draconis Variable:
- BYORP:
- BZ:
- C:
- Caldwell Catalog: small catalog for amateur astronomers as an adjunct to the Messier Catalog
- Carbon (C): element, C, atomic number 6
- C Chondrite:
- C-Band All Sky Survey:
- C-BASS:
- C-H:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- C-Type Shock:
- Shock Wave: abrupt propagating disturbance in a fluid
- C2H2:
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- C2H4:
- Ethylene (C2H4): compound of two carbon and four hydrogen atoms
- CP:
- Specific Heat: Ratio of added temperature to added heat for a material
- CV:
- Specific Heat: Ratio of added temperature to added heat for a material
- C+: ionized carbon missing one electron
- Carbon (C): element, C, atomic number 6
- Ca:
- Calcium (Ca): element, Ca, atomic number 20
- Ca I:
- Calcium (Ca): element, Ca, atomic number 20
- Ca II:
- Calcium (Ca): element, Ca, atomic number 20
- Cadence: period between observations
- CAESAR: planned space mission to return a sample of a comet
- CAI: calcium/aluminum specs in chondrites
- Calán/Tololo Supernova Search:
- Calán/Tololo Survey: late 1980s to early 1990s search to redshift .1
- Calar Alto Legacy Integral Field Area Survey:
- CALIFA: spectroscopic map of 600 galaxies
- Calar Alto Observatory:
- CALIFA: spectroscopic map of 600 galaxies
- Calcium (Ca): element, Ca, atomic number 20
- Calcium Carbonate:
- Calcium Silicate:
- Calcium-Aluminum-Rich Inclusion:
- CAI: calcium/aluminum specs in chondrites
- Calcium-rich Gap Transient: type of explosive event larger than a nova and smaller than a supernova
- Calcium-rich Supernova:
- Caldwell:
- Caldwell Catalog: small catalog for amateur astronomers as an adjunct to the Messier Catalog
- Caldwell 5:
- IC 342: spiral galaxy in the Council of Giants
- Caldwell Catalog: small catalog for amateur astronomers as an adjunct to the Messier Catalog
- CALIFA: spectroscopic map of 600 galaxies
- California:
- California-Kepler Survey (CKS): followup to Kepler to determine stellar radii
- Callisto: well-known Jupiter moon
- CalTech:
- CAMB:
- CMBFast: software to calculate CMB anisotropies
- Cambridge Catalog of Radio Sources: series of catalogs of northern hemisphere sources
- Cambridge Interferometer:
- Cambridge Optical Aperture Synthesis Telescope:
- COAST: optical interferometer in England
- camera:
- GISMO: 2 mm bolometer camera on IRAM 30m telescope
- MUSTANG: bolometer array on the Green Bank Telescope
- QUEST: sixteen square-degree survey camera
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- cameras:
- CAMS:
- ASTRO-H: Japanese space x-ray telescope
- Canada:
- Canada-France Brown Dwarfs Survey:
- CFBDS: survey in search of brown dwarfs
- Canada-France-Hawaii Telescope (CFHT): 3.6 meter optical/infrared telescope in Hawaii
- CFHTLS: surveys of transients and stars
- Canada-France-Hawaii Telescope Legacy Survey:
- CFHTLS: surveys of transients and stars
- Canadian Hydrogen Intensity Mapping Experiment (CHIME): radio telescope mapping distant neutral hydrogen
- Canadian Institute for Theoretical Astrophysics (CITA,ICAT): national research organization at University of Toronto
- Canadian Space Agency:
- CSA: Canadian agency includes astronomical research
- CanariCam:
- Canary Islands:
- CANCAM:
- CAESAR: planned space mission to return a sample of a comet
- CANDELS:
- Canis Major Dwarf Galaxy: small irregular galaxy in the Local Group
- Canopus: second brightest star in the sky
- CAPS:
- Cassini: explorer spaceship sent to Saturn
- Capture Theory:
- Captured Rotation:
- Carbide Planet:
- Carbon Planet: theoretical planet-type with more carbon than oxygen
- Carbon (C): element, C, atomic number 6
- Carbon 14:
- Carbon and Monosulfide:
- Tracer: chemical whose presence indicates the presence of another chemical
- Carbon Burning:
- Carbon Cycle:
- Carbon Dating:
- Carbon Dioxide (CO2): compound of carbon atom and two oxygen atoms
- Carbon Monoxide (CO): compound of carbon and oxygen, one atom each
- Carbon Monoxide Mapping Array (COMA): planned experiment to observe epoch of reionization
- Carbon Monoxide Power Spectrum Survey:
- COPSS: survey of CO from star forming epoch
- Carbon Planet: theoretical planet-type with more carbon than oxygen
- Carbon Star: star with more carbon than oxygen in its atmosphere
- Carbon to Oxygen ratio:
- Carbon (C): element, C, atomic number 6
- Carbon-Oxygen White Dwarf:
- White Dwarf: stellar remnant of mostly electron-degenerate matter
- Carbon-Silicate Cycle:
- Weathering: changes in surface due to contact with atmosphere
- Carbonaceous Chondrite (C Chondrite): stony meteorites with carbon compounds showing no melting
- Carbonate:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Carbonate System: system governing water and CO2 in the presence of each other
- Carbonate System: system governing water and CO2 in the presence of each other
- Carbonate-Silicate Cycle: reversible carbon/silicon chemical reaction
- Carbonic Acid:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Carbonate System: system governing water and CO2 in the presence of each other
- Carbyne:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Carl Sagan Institute (CSI): group researching finding life on other planets and moons
- CARMA:
- CARMA EDGE: CO survey of galaxies
- CARMA Extragalactic Database for Galaxy Evolution:
- Carrington Event: solar storm September 1-3 1859
- Cas A:
- Cassegrain Reflector: reflecting telescope with convex secondary mirror
- Cassini: explorer spaceship sent to Saturn
- Cassini Equinox:
- Cassini: explorer spaceship sent to Saturn
- Cassini Solstice:
- Cassini: explorer spaceship sent to Saturn
- Cassini-Huygens:
- Cassini: explorer spaceship sent to Saturn
- Cassiopeia A: supernova remnant visible for 300 years
- CASTRO: hydrodynamics simulation software
- Casually Connection Regions:
- Inflation: theorized rapid expansion of the very early universe
- CAT:
- Cataclysmic Variable:
- Cataclysmic Variable Star (CV): star whose magnitude is much larger on occasion
- Catalina Real-time Transient Survey:
- Catalina Sky Survey (CSS): survey of near-Earth objects
- Catalog:
- 87GB Catalog of Radio Sources (87GB): 1980s Green Bank radio survey
- Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
- Aitken Double Star Catalogue (ADS): 1932 catalog with multiple star systems and non-orbiting double stars
- Arakelian Catalog (Ark): 1970s list of small/bright galaxies
- Arecibo Occultation Survey (AO): 1960s radio survey using occultations by the moon
- Arp-Madore Catalog of Southern Peculiar Galaxies (AM): 1970s-1980s catalog from the UK Schmidt Survey
- Asiago Supernova Catalog (B/SN): 1999 catalog of known supernovae and their galaxies
- Astronomical Catalog: lists of observed astronomical bodies and their characteristics
- Atlas of Galactic Nebulae (GN): 1980s catalog of Milky Way nebulae
- Atlas of Peculiar Galaxies (APG): 1960s catalog-book with photos
- Barnard Catalog (Barnard,B): 1919 catalog of dark nebulae
- Basel Open Cluster Catalog (Basel): list of open clusters
- Becker, White, and Edwards Catalog (BWE): 1990s radio catalog from a 91m Green Bank Telescope survey
- Berkeley Open Cluster Catalogue (Be): list of open clusters
- Bonner Durchmusterung Catalog (BD): well-known astrometric catalog from late 1800s
- Bright Star Catalog (HR,BS,YBS): early 20th century catalog of 9000 stars
- Caldwell Catalog: small catalog for amateur astronomers as an adjunct to the Messier Catalog
- Cambridge Catalog of Radio Sources: series of catalogs of northern hemisphere sources
- Catalog of Azzopardi & Vigneau (AzV): probable stars in the SMC
- Catalog Of Galaxies And Clusters Of Galaxies (CGCG): list of galaxies/clusters assembled in 1960s
- Catalogue of Galactic Planetary Nebulae (PK,PK67): 1967 catalog
- Catalogue of Interacting Galaxies (VV): begun in the 1950s
- Cederblad Catalog (Ced): list of bright nebulae
- Collinder Catalog (Cr): 1930s catalog of 471 open clusters
- Cosmic Lens All-Sky Survey (CLASS): 1990s radio survey aimed at gravitational lenses
- CRATES: catalog of 8.4GHz data on radio sources
- Czernik Catalog (Cz): list of open clusters
- David Dunlap Observatory Catalog (DDO): catalog of dwarf galaxies
- Dickel-Wendker-Bieritz Catalog (DWB): list of HII regions in the Cygnus X star forming region
- Dolidze-Dzimselejsvili Catalogue (DoDz): list of 11 open clusters
- ESO/Uppsala Survey Of The ESO (B) Atlas: 1970s southern all-sky survey
- Fairall Galaxy List (Frl,Fairall): 1977 list of galaxies with bright nuclei
- Fourth Cambridge Catalog of Radio Sources (4C): 1960s catalog of northern hemisphere 178MHz sources
- Frank Ross's Catalog: high-proper-motion and variable stars catalogued by Frank Ross
- General Catalogue of Variable Stars (GCVS): 20th/21st century catalog of 58000 variable stars
- Gliese-Jahreiss Catalog (GJ): 1991 catalog of stars within 25 parsecs
- Green Bank 6-cm Radio Source Catalog (GB6): catalog of from 1980s northern-hemisphere radio survey
- Guide Star Catalog (GSC,HSTGC): catalog of stars to help aim HST
- Henry Draper Catalog (HD): early 20th century spectroscopic catalog of stars
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
- King Catalog: list of 21 open clusters
- Luyten Half-Second Catalog (LHS): 1979 catalog of 4000 stars with high proper motion
- Lynds Bright Nebula Catalog (LBN): 1950s/1960s list of bright nebulae found on Palomar plates
- Lynds Catalog of Dark Nebulae (LDN,L): 1950s/1960s list of dark nebulae found on Palomar plates
- MASH Catalog of Planetary Nebulae: 995 possible planetary nebulae
- Max Wolf's Catalog of Stars With Proper Motion: early 20th century catalog of 1500 stars
- Melotte Catalog: 1915 catalog of open and globular clusters
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- MIT X-ray Burst Source Catalog (MXB): 1970s catalog of X-ray bursters
- Morphological Catalogue Of Galaxies (MCG): 1960s catalog from Palomar plates
- New General Catalogue (NGC): 1888 catalog of galaxies, star clusters, and other nebulae
- NOMAD: astrometric star catalog
- Ohio Radio Survey: 1960s radio survey by Ohio State University
- Palomar Globular Clusters (Pal): list of 15 globular clusters found in POSS plates
- Parkes Catalog (PKS): catalog of from 1960s-1990 of radio sources in southern hemisphere
- Parsamian Nebula Catalog: 1965 list of nebulae
- Polar-Ring Catalog (PRC): 1990 catalog of polar-ring galaxies
- Principal Galaxies Catalog (PGC): modern catalog of more than 70k galaxies
- RASS/Green Bank Catalog (RGB,RASSGB): combined list of radio galaxies from Rosat and Green Bank surveys
- Roma-BZCAT: 2013 catalog of blazars
- Sharpless Catalog (Sh2): catalog of HII regions found on Palomar plates
- Strasbourg-ESO Catalog of Galactic Planetary Nebulae (PNG): 1992 catalog of 1820 objects
- Struve Catalogs: two catalogs of double stars
- Texas Survey of Radio Sources at 365 MHz (TXS): 1970s/1970s radio survey made with the Texas Interferometer
- Third Cambridge Catalogue of Radio Sources (3C): 1959 catalog of northern hemisphere 159MHz sources
- Transient Name Server (TNS): online catalog of transients
- Uppsala General Catalogue (UGC): 1979 catalog of galaxies visible from northern hemisphere
- USS Sources: catalog of sources with steep spectral index
- Van Den Bergh Reflection Nebula Catalog (vdB): catalog of reflection nebulae found in POSS plates
- Villanova White Dwarf Catalog: ongoing catalog of white dwarfs
- WISeREP: interactive catalog of supernovae
- Catalog of Azzopardi & Vigneau (AzV): probable stars in the SMC
- Catalog Of Galaxies And Clusters Of Galaxies (CGCG): list of galaxies/clusters assembled in 1960s
- Catalog-based Designator:
- catalogs:
- Astrocats: software to create and manage an astronomy catalog
- Astronomical Catalog: lists of observed astronomical bodies and their characteristics
- Catalogue:
- Catalogue des Nebuleuses et des Amas d'Etoiles:
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- Catalogue of Bright Nebulae:
- Catalogue Of Cometary nebulae discovered on Palomar maps:
- Catalogue of Galactic Planetary Nebulae (PK,PK67): 1967 catalog
- Catalogue of Interacting Galaxies (VV): begun in the 1950s
- Catalogue of Nearby Stars:
- Catalogue of Nebulae and Clusters of Stars:
- Catalogue of Nebulae and Star Clusters:
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- Catalogue of Rich Clusters of Galaxies:
- Catalogus Britannicus:
- CATS345:
- CBR:
- CCAT: 25 meter submillimeter telescope planned for Chile
- Atacama Desert: high altitude, dry plateau in Chile, the site of observatories
- CCAT Prime (CCAT-p): planned 6 meter submillimeter telescope in Chile
- CCAT-p:
- Atacama Desert: high altitude, dry plateau in Chile, the site of observatories
- CCAT Prime (CCAT-p): planned 6 meter submillimeter telescope in Chile
- CCD: electronic device to detect light
- cD Galaxy:
- CDA:
- Cassini: explorer spaceship sent to Saturn
- CDF-S:
- CDFS:
- CDISORT:
- DISORT: simulation of radiative transfer in an atmosphere
- CDM:
- CDS:
- CE:
- CEA:
- CEA SAp:
- CEA Service d'Astrophysique (CEA SAp): French national astrophysics research institute
- CEB:
- CEBE:
- Ced:
- Cederblad:
- Cederblad Catalog (Ced): list of bright nebulae
- Celestial Coordinate System: system for specifying position of celestial objects
- Celestial Equator: equator-like line around the celestial sphere
- Celestial Mechanics: study of forces and motion of celestial objects
- Celestial Pole:
- Celestial Sphere: the sky in considered as a sphere surrounding the observer
- CELIAS:
- Cell:
- Hadley Cell: circulation pattern of up at the equator, out, down, and back
- Zonal Flow: east-west air circulation
- Zone: apparent "horizontal" band in an atmosphere
- Centaur: asteroid-like body orbiting among the outer planets
- 10199 Chariklo: largest minor planet in the outer solar system
- LCROSS: space probe observing the lunar poles
- Centaurus:
- Centaurus A:
- Center for Astronomy of Heidelberg University:
- Center for High Angular Resolution Astronomy:
- CHARA: optical interferometer
- Center Of Mass:
- Barycenter: center of mass of two orbiting bodies
- Reduced Mass: the reciprocal of the sum of the reciprocals of the masses of two objects
- Center Of Mass Frame Of Reference:
- Centimeter-Gram-Second System of Units:
- CGS: metric system variant
- Centimeter-Wave Astronomy:
- Central Limit Theorem:
- Centre national d'ètudes spatiales (CNES): French space agency
- Cepheid:
- Cepheid Variable: star varying with a constant period
- Ceres:
- Asteroid: minor planet without comet characteristics
- Dwarf Planet: round like a planet, only smaller
- Protoplanet: simplest, least-developed object classified as a planet
- Cerro Armazones Observatory:
- Cerro Chajnantor Atacama Telescope:
- CCAT: 25 meter submillimeter telescope planned for Chile
- Cerro Tololo:
- Cerro Tololo Inter-American Observatory (CTIO): observatory near Amado, Arizona
- CfA Redshift Survey:
- CfA2 Great Wall:
- CFBDS: survey in search of brown dwarfs
- CFBDSIR:
- CFBDS: survey in search of brown dwarfs
- CFHT:
- CFHTLS: surveys of transients and stars
- CFL Condition:
- CGB:
- CGCG:
- CGM:
- CGRO:
- CGS: metric system variant
- Erg: CGS unit of energy
- Gauss (G,Gs): measurement of magnetic field β
- Jansky (Jy): unit of measurement of spectral flux density
- Magnetic Flux (B): total magnetism passing through a surface
- Magnetic Flux Density (B): vector field describing magnetism in relation to the Lorentz force
- SI: modern metric system
- CGS4:
- CH:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- CH Star:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- CH4:
- Methane (CH4): compound of one carbon and 4 hydrogen atoms
- CHAI:
- CCAT: 25 meter submillimeter telescope planned for Chile
- CCAT Prime (CCAT-p): planned 6 meter submillimeter telescope in Chile
- Chandra:
- Chandra Deep Field South (CDFS,CDF-S): highly-detailed X-ray image of small region of the sky taken by Chandra
- Chandra X-ray Observatory (CXO): space x-ray telescope
- Chandrasekhar Friction:
- Chandrasekhar Limit: maximum mass of a white dwarf
- ChaNGa:
- chaos:
- Lyapunov Time: timescale over which a dynamical system is chaotic
- Chaos Theory: theory of systems highly sensitive to initial conditions
- CHARA: optical interferometer
- Characterizing Exoplanet Satellite:
- CHEOPS: space telescope in development to measure radii of exoplanets
- Charge:
- Charge-Coupled Device:
- CCD: electronic device to detect light
- Charging Barrier:
- Chariklo:
- Charm:
- Charon:
- Moon: Earth's natural satellite
- Pluto: dwarf planet formerly listed as one of the nine planets
- Chemical Differentiation:
- Chemical Equilibrium (CE): state where chemical makeup is unchanging
- Chemical Kinetics:
- Chemical Species:
- Chemisorption:
- chemistry:
- Abiotic Oxygen: oxygen from non-life sources
- Abundances: relative amounts of each chemical element
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- Adsorption: adhesion to a surface
- Amine: type of compound containing nitrogen
- Ammonia (NH3): compound of nitrogen and hydrogen
- Bulk Density: total mass divided by total volume
- Calcium (Ca): element, Ca, atomic number 20
- Carbon (C): element, C, atomic number 6
- Carbon Dioxide (CO2): compound of carbon atom and two oxygen atoms
- Carbon Monoxide (CO): compound of carbon and oxygen, one atom each
- Carbonate System: system governing water and CO2 in the presence of each other
- Carbonate-Silicate Cycle: reversible carbon/silicon chemical reaction
- Chemical Equilibrium (CE): state where chemical makeup is unchanging
- Chemodynamics: study of the dynamics of chemical reactions
- Clathrate: crystal lattice with voids that can trap molecules
- Diffusion: the spreading of particles toward an even distribution
- Energetic Neutral Atom (ENA): high-speed neutral atom
- Equilibrium Condensation Model: chemical model explaining solar system planet abundances
- Ethylene (C2H4): compound of two carbon and four hydrogen atoms
- Fractionation: separation of compounds from a mixture
- Fractionation Factor: isotope quantity
- Geochemistry: the chemistry of the Earth, planets, and moons
- Glycine (Gly,G): smallest of the twenty common amino acids
- Helium (He): non-metallic element, He, atomic number 2
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Hydrogen (H): most prominent element, atomic number 1
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- Ice: solid state of water
- Iron (Fe): metal, Fe, atomic number 26
- Lithium (Li): metal, Li, atomic number 3
- Methane (CH4): compound of one carbon and 4 hydrogen atoms
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Milky Way Chemical Evolution: process of the development of metals in the Milky Way
- Molecular Handedness: mirror-image forms of some molecules
- Nickel (Ni): metal, Ni, atomic number 28
- Nitrite (NO2-): ion of a nitrogen atom and two oxygen atoms with extra electron
- Nitrogen (N): metal, N, atomic number 7
- Number Density: number of objects per volume
- Oxidation State: number characterizing atoms of a compound as ions
- Oxygen (O): element, O, atomic number 8
- PAH Emissions: infrared emission from polycyclic aromatic hydrocarbons in gas clouds
- Photochemistry: study of the chemical effects of light
- Photodissociation: chemical reaction in which photons break chemical bonds
- Polycyclic Aromatic Hydrocarbon (PAH): hydrocarbons consisting of meshes of benzene rings
- Reducing Atmosphere: atmosphere lacking oxygen or other oxidizers
- Reduction Potential (Eh,ORP,pE): measure of a chemical species' tendency to acquire electrons
- Refractory Material: material with high condensation temperature
- Siderophile: material that dissolves in molten iron
- Silicon (Si): metal, Si, atomic number 14
- Sodium (Na): metal, Na, atomic number 11
- SPECTRE: an interactive spectrum analysis software package
- Stellar Population: grouping of stars according to metallicity
- Sulfur (S): metal, S, atomic number 16
- Surface Reaction: such as reactions between gas and adjacent liquid
- Titration: analyzing a chemical solution by color change
- Chemodynamics: study of the dynamics of chemical reactions
- CHEOPS: space telescope in development to measure radii of exoplanets
- Cherenkov Cone:
- Cherenkov Radiation: radiation from the shock of a charged particle passing through a medium
- Cherenkov Telescope Array (CTA): planned ground gamma-ray telescope array
- Chi Draconis A:
- F-Type Star (F): type of star with about 1.5 times the mass of the Sun
- Chi-Squared:
- Chi-Squared Test (χ² Test): statistical significance test
- Chile:
- CHIME:
- CHIMERA:
- China:
- FAST: Arecibo-like 500m telescope in deployment in China
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- Chirality:
- Chirp: burst of signal rising or falling in frequency
- Chloride:
- Geochemistry: the chemistry of the Earth, planets, and moons
- Chlorine:
- Geochemistry: the chemistry of the Earth, planets, and moons
- Chondrite: stony meteorites showing no melting
- Chondrule:
- CAI: calcium/aluminum specs in chondrites
- Chondrite: stony meteorites showing no melting
- Chromatic Dispersion:
- Chromium:
- Chromosphere: middle layer of the Sun's atmosphere
- CHZ:
- CI:
- CIB:
- Cigar Galaxy:
- M82: nearby starburst galaxy
- CII:
- CIII:
- CIRCE:
- Circinus Galaxy (ESO 97-G13): nearest Seyfert galaxy
- Circle:
- Conic Section: orbit shapes, like the intersection of a plane and cone
- Circular Polarization:
- Circular Polarization Radar:
- Circular Polarization Ratio (CPR): ratio of circular polarization handedness in reflected radar signal
- Circumbinary Planet: exoplanet orbiting two stars
- Circumgalactic Medium (CGM): gas surrounding a galaxy
- Circumplanetary Disk: disk of dust and gas around a planet
- Circumstellar Disk: disk or ring shaped accumulation of matter around a star
- circumstellar habitable zone:
- Circumstellar Material:
- CIRS:
- CITA:
- CIVA:
- Rosetta: space probe that visited a comet
- CKS:
- CKS-COOL:
- Cl:
- CLASS:
- Class 0 YSO:
- Class I YSO:
- Class II YSO:
- Class III YSO:
- Classical Cepheid:
- Classical KBO:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Classical Kuiper Belt Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Classical Mechanics:
- Classical Nova:
- Nova: white dwarf explosion
- classification:
- Clathrate: crystal lattice with voids that can trap molecules
- Clathrate Hydrate:
- Clathrate: crystal lattice with voids that can trap molecules
- Clay Telescope:
- CLF:
- climate:
- Climate Change:
- Earthshine: reflected and electromagnetic radiation from Earth
- Climate Model:
- Clio2:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Close Binary Star:
- Closed Magnetic Field Lines:
- Closed Universe:
- cloud:
- Cloud Fragmentation: clumping in clouds due to gravitational instability
- Cloud Mass Function:
- cloud type:
- clouds:
- Clump:
- Clump Mass Function:
- Cluster:
- Galaxy Cluster (CL): large group of galaxies gravitationally-bound to the group
- Cluster Dark Matter Halo:
- Cluster Fitting:
- Cluster Radius: radius of a galaxy cluster
- CMA:
- CMa Dwarf:
- CMB:
- CMB Cold Spot:
- CMB Halo Weak Lensing:
- Weak Lensing: slight lensing detected in random patterns of distant objects
- CMB Lensing: gravitational lensing of the CMB
- CMB Polarization: effects of scattering and lensing on the CMB
- CMB Stage-4 (CMB-S4): planned follow-on to mid-2010s CMB observations
- CMB-S4:
- CMB Stage-4 (CMB-S4): planned follow-on to mid-2010s CMB observations
- CMBFast: software to calculate CMB anisotropies
- CMD:
- CME:
- CMF:
- CN:
- CN Leonis:
- CNB:
- CNES:
- CNO Cycle: fusion reaction chain turning hydrogen and nitrogen into helium and nitrogen
- CNRS:
- CO:
- CO J Ladder:
- CO Ladder:
- CO Legacy Database for GASS:
- COLD GASS: survey of CO in nearby large galaxies
- CO Mapping Array Pathfinder:
- COMAP: high frequency radio telescope to map CO
- CO Rotational Ladder:
- CO to H2 Factor (Xco,XCO): assumed ratio between observed CO emission lines and H2 mass
- CO2:
- COAST: optical interferometer in England
- Coastal Kelvin Wave:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- COB:
- COBE:
- Code: astrophysical modeling computer program
- AREPO: cosmology simulation using moving mesh technique
- AstroBEAR: MHD simulation system
- Athena: MHD code
- ATLAS Stellar Model: computer model of a stellar photosphere
- BT-Settl: model atmosphere of small stars and brown dwarfs
- CASTRO: hydrodynamics simulation software
- DISORT: simulation of radiative transfer in an atmosphere
- Enzo: hydrodynamic simulation system
- FLASH: hydrodynamic simulation system
- FORNAX: hydrodynamics simulation software
- GR1D: core collapse supernova simulation in 1D with GR
- Hyperion: Monte-Carlo radiative transfer code
- MagIC: numerical code to for fluid dynamics including dynamos
- PHOENIX Stellar Model: computer model of a stellar photosphere
- PROMETHEUS/VERTEX: hydrodynamic simulation system
- RAMSES: hydrodynamic simulation system
- SpEC: code to solve general relativity problems
- StarTrack: stellar population synthesis code
- Turtlebeach: radiative transfer code
- Code for Anisotropies in the Microwave Background:
- CMBFast: software to calculate CMB anisotropies
- CODEX:
- coefficient:
- Absorption Coefficient: measure of how much light a substance absorbs
- J2: geopotential coefficient regarding a planet's oblateness
- Coeval: the same age
- Coherence:
- Coherent Dense Core:
- Coherent Light: beam of light at a single frequency
- Cold Dark Matter (CDM): one of three "dark matter" theories
- Dark Matter: matter hypothesized to provide galaxies with mass that can't be viewed
- Cold Gas: gas cool enough to form galaxies and stars
- COLD GASS: survey of CO in nearby large galaxies
- Cold Mass Accretion (CMA): stellar accretion through an accretion disk
- Cold Spot: unusually colder spot in the CMB
- Cold Start:
- Cold Trap: layer of atmosphere that prevents a gas from escaping by freezing it
- Collapsar:
- Collimate:
- Collimated Light:
- Collimator: device to align beams of light
- Collinder:
- Collinder 50:
- Collinder Catalog (Cr): 1930s catalog of 471 open clusters
- collision:
- Collision Cross Section:
- Cross Section: "area" representation of probability of an interaction of particles
- Collisional Broadening:
- color:
- Color Excess:
- Color Index: a number that characterizes the color of an object
- Reddening: red appearance of astronomical objects because blue light is attenuated by dust
- Color Index: a number that characterizes the color of an object
- Color Temperature:
- Color-Color Diagram: means of comparing characteristics of stars
- Color-Magnitude Diagram (CMD): diagram relating color to luminosity
- Color-Period Diagram: means of comparing periods of stars at various wavelengths
- Column Density: measure of the matter through which EMR is passing
- Column Mass Density:
- Column Number Density:
- Coma: aberration where points of light show a tail
- Coma Cluster:
- Coma Filament:
- Coma Supercluster: nearby supercluster
- Coma Wall:
- COMAP: high frequency radio telescope to map CO
- Comatic Aberration:
- Coma: aberration where points of light show a tail
- Combined Array for Research in Millimeter-wave Astronomy (CARMA): array of radio telescopes in eastern California
- Combined Radio All-Sky Targeted Eight-GHz Survey:
- CRATES: catalog of 8.4GHz data on radio sources
- ComCam:
- Comet: Sun-orbiting object with coma and possible tail
- Comet Astrobiology Exploration Sample Return:
- CAESAR: planned space mission to return a sample of a comet
- Comet Galaxy: spiral galaxy in cluster Abell 2667
- Comet Halley:
- Comet: Sun-orbiting object with coma and possible tail
- Comet P/Shoemaker-Levy:
- Comet: Sun-orbiting object with coma and possible tail
- Comet Planet: planet with some characteristics of a comet
- Cometary Nebula:
- Comets:
- Asteroid: minor planet without comet characteristics
- CAESAR: planned space mission to return a sample of a comet
- Centaur: asteroid-like body orbiting among the outer planets
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Oort Cloud: cloud of comets and minor planets around the solar system
- Rosetta: space probe that visited a comet
- Stardust: space mission to collect comet coma dust
- Striae: parallel ridges
- COMICS:
- Commissariat à l'énergie atomique et aux énergies alternatives:
- Common Envelope:
- Common Envelope Binary:
- Common Envelope Binary Event:
- Commonwealth Scientific and Industrial Research Organisation:
- Comoving Coordinates:
- Comoving Density of Star Formation:
- Comoving Distance:
- Comoving Horizon:
- Comoving SFR Density:
- Comoving SFRD:
- Comoving Space Density:
- Comoving Star Formation Rate Density:
- Comoving Units: units of measure that incorporate the Hubble Constant
- Compact Binary:
- Compact Group:
- Galaxy Group: group of fifty or fewer gravitationally bound milky-way-sized galaxies
- Compact Object: dense astronomical body such as white dwarf or denser
- Compact Object Binary:
- Compact Object Merger:
- compact objects:
- Compact Stellar Nucleus:
- COMPLETE Survey: survey of star forming regions
- Completeness: measure of how many of a survey's objects of a certain magnitude have been detected
- Completeness Limit:
- Completeness: measure of how many of a survey's objects of a certain magnitude have been detected
- Complex:
- Composite Boson:
- compound:
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- Amine: type of compound containing nitrogen
- Ammonia (NH3): compound of nitrogen and hydrogen
- Carbon Dioxide (CO2): compound of carbon atom and two oxygen atoms
- Carbon Monoxide (CO): compound of carbon and oxygen, one atom each
- Ethylene (C2H4): compound of two carbon and four hydrogen atoms
- Glycine (Gly,G): smallest of the twenty common amino acids
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- Methane (CH4): compound of one carbon and 4 hydrogen atoms
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Nitrite (NO2-): ion of a nitrogen atom and two oxygen atoms with extra electron
- Polycyclic Aromatic Hydrocarbon (PAH): hydrocarbons consisting of meshes of benzene rings
- COMPTEL:
- Compton Cooling:
- Compton Scattering: photon collision with a charged particle that emits a different photon
- Compton Effect:
- Compton Scattering: photon collision with a charged particle that emits a different photon
- Compton Gamma Ray Observatory (CGRO): observatory-satellite for detecting gamma rays
- Compton Scattering: photon collision with a charged particle that emits a different photon
- Comptonization:
- Compton Scattering: photon collision with a charged particle that emits a different photon
- Computation:
- Computational Astrophysics: astrophysical study through computer modeling
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- computing:
- concept:
- CONCERTO: spectrometer aimed at mapping the [CII] line
- Condensation Temperature:
- Conditional Luminosity Function (CLF): function characterizing luminosity of galaxies with a given halo mass
- Conditional Mass Function:
- Conditional Stellar Mass Function (CSMF): function characterizing galaxies within a halo of a given mass
- Conduction:
- Conductive Hydrogen:
- Metal: in astrophysics, any element more massive than helium
- configuration:
- Conic Section: orbit shapes, like the intersection of a plane and cone
- Conjunction:
- CONSERT:
- Rosetta: space probe that visited a comet
- Conservation Law: property that remains unchanged by physical phenomena
- consortium:
- constant:
- constellation:
- Orion: well-known constellation in the northern hemisphere
- Constitutive Equations:
- Constitutive Relations:
- construction:
- Contact Binary:
- Contamination:
- Completeness: measure of how many of a survey's objects of a certain magnitude have been detected
- Continuous Absorption: the absorption of a whole section of a spectrum
- Continuous Galerkin Method:
- Continuous Random Variable:
- Continuous shock:
- Shock Wave: abrupt propagating disturbance in a fluid
- Continuous Spectrum: smooth spectrum or portion of spectrum with no lines
- Continuous Viewing Zone (CVZ): region of sky that can be viewed 7x24x365
- Continuous-Wave Frequency-Modulation:
- continuum:
- Continuum Emission: continuous spectrum such as black body radiation or bremsstrahlung
- Convection:
- Convective Mantle:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Convective Parameterization:
- Convective Rossby Number:
- Convergent Point:
- Convergent Point Method:
- Convolution: type of product function of two functions
- Cooling Function: function relating a gas's cooling rate to its temperature
- Cooling Timescale:
- Giant Planet: planet of more than 10 Earth masses
- Timescale (t,τ): general length of time something takes
- coordinate:
- Declination (dec): direction coordinate above/below celestial equator
- Epoch: time on which to base celestial coordinates
- Meridian: circle around the Earth passing through both poles
- Right Ascension (RA): direction coordinate along celestial equator
- Terrestrial Time (TT): current measure of time for astronomical observations on Earth
- Coordinate Distance:
- coordinate system:
- Coordinated Molecular Probe Line Extinction Thermal Emission Survey:
- coordinates:
- Coplanar Flip:
- COPSS: survey of CO from star forming epoch
- Cordelia:
- Core:
- Core Accretion:
- Core Accretion Model: model for the formation of giant planets
- Core Barrier:
- Core Collapse Supernova: supernova resulting from the collapse of the core of a star
- Core Flash:
- Core Mass Function:
- Core-Mantle Boundary:
- Coriolis Effect:
- Coriolis Force: apparent force in a rotation frame of reference
- Hadley Cell: circulation pattern of up at the equator, out, down, and back
- Coriolis Force: apparent force in a rotation frame of reference
- CorMASS: near-infrared spectrograph
- Cornell:
- Cornell Caltech Atacama Telescope:
- CCAT: 25 meter submillimeter telescope planned for Chile
- Cornell Massachusetts Slit Spectrograph:
- CorMASS: near-infrared spectrograph
- Corona: plasma surrounding a star
- Coronagraph: telescope feature to block light from a specific body
- Coronagraphy:
- Coronagraph: telescope feature to block light from a specific body
- Coronal Loop:
- Coronal Mass Ejection (CME): mass of plasma ejected from the Sun
- Coronal Solar Magnetism Observatory (COSMO): proposed solar observatory
- COROT: observatory-satellite to look for transiting exoplanets and stellar oscillations
- Corotation Resonance (CR): an orbital resonance with the same frequency as the orbit
- Corotation Torque: torque on a planet from coorbiting planetary disk material
- Corrective Optics Space Telescope Axial Replacement:
- Correlation Function:
- Correlator: unit that interferes wave signals for interferometry
- CORSA-b:
- Corvus:
- COS:
- COSAC:
- Rosetta: space probe that visited a comet
- COSIMA:
- Rosetta: space probe that visited a comet
- COSMIC:
- Cosmic Anisotropy Telescope (CAT): 1990s interferometer to measure CMB variations
- Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS): early universe survey by HST
- Cosmic Background Explorer (COBE): 1989 satellite for looking at the CMB
- Cosmic Background Radiation (CBR): electromagnetic radiation coming from every direction
- Cosmic Censorship Hypothesis:
- Cosmic Distance:
- Cosmic Distance Ladder: series of methods of measuring distance to astronomical objects
- Cosmic Distance Scale:
- Cosmic Dust: cosmic dust is dust in space such as interstellar dust
- Cosmic Dust Analyzer:
- Cassini: explorer spaceship sent to Saturn
- Cosmic Evolution Survey (COSMOS): investigation of dark matter and the universe's large scale structure
- Cosmic Explorer: concept for a very large LIGO-like GW detector
- Cosmic Gamma Ray Background (CGB): gamma-ray radiation seen everywhere
- Cosmic High Noon:
- Cosmic Inflation:
- Inflation: theorized rapid expansion of the very early universe
- Cosmic Infrared Background (CIB): widespread infrared radiation not associated with known sources
- Cosmic Lens:
- Current Sheet: narrow sheet within a magnetic field where current flows
- Cosmic Lens All-Sky Survey (CLASS): 1990s radio survey aimed at gravitational lenses
- Cosmic Light Horizon:
- Cosmic Microwave Background (CMB): microwave radiation coming from every direction
- Cosmic Microwave Background Radiation:
- Cosmic Neutrino Background:
- Cosmic Optical Background (COB): widespread optical radiation not associated with known sources
- Cosmic Ray Spallation:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- Cosmic Ruler:
- Cosmic String: rent in spacetime
- Cosmic Time: time since the big bang
- Cosmic Time Dilation:
- Cosmic Void:
- Void: empty spaces between large scale structures
- Cosmic Web:
- Cosmic X-Ray Background (CXB): x-ray radiation coming from outside the Milky Way
- Cosmic X-Ray Background Radiation:
- COSMO:
- Cosmological:
- Cosmological Band Shifting:
- Cosmological Constant (Λ): force counteracting the universe's inward gravitational pull
- Cosmological Distance Ladder:
- Cosmological Horizon:
- Cosmological Inflation:
- Inflation: theorized rapid expansion of the very early universe
- Cosmological Principle: physics and the overall view of things is the same everywhere
- Cosmological Redshift:
- Redshift (z): change to longer wavelengths due to Doppler affects
- Cosmological Simulation:
- Cosmological Time Dilation: very distant events appear to take longer
- Cosmological Zoom Simulation: cosmological simulation plus higher resolution simulations of selected space
- Cosmology: study of the life of the universe
- COSMOS:
- COSTAR:
- COSTEP:
- Coudé Focus:
- Coudé Focus Telescope: type of Nasmyth telescope with additional mirrors
- Coulomb:
- Tesla (T): unit of magnetic flux density
- Coulomb Force:
- Coulomb Scattering:
- Coulomb's Constant:
- Coulomb's Law: static electrical force relation
- Council Of Giants: twelve large galaxies surrounding the Local Group
- Courant Condition:
- Courant-Friedrichs-Lewy-Condition:
- Covalent Bond:
- CP Symmetry:
- Axion (A0): proposed light, electrically neutral elementary particle
- CPR:
- CR:
- Crab Nebula (M1): supernova remnant in Taurus
- Crab Pulsar:
- CRaTER:
- CRATES: catalog of 8.4GHz data on radio sources
- CRIRES: high resolution IR echelle spectrometer
- CRIRES+:
- CRIRES: high resolution IR echelle spectrometer
- CRIS:
- CRISM:
- Critical Density (ρc): density of the universe which leaves it flat
- Critical Density of the Universe:
- Critical Radius:
- Critical Velocity:
- Cross Dispersion Spectrograph: echelle spectrograph with additional disperser crosswise to the first
- Cross Dragone Design:
- Cross Section: "area" representation of probability of an interaction of particles
- crowdsource:
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- Planet Hunters (PH): crowdsourcing website to identify galaxy types from surveys
- CRS:
- Voyager: space probes to observe planets and the edge of the solar system
- CRTS:
- Crustal Magnetism: magnetic fields independent of a world's core magnetic field
- Crustal Plates: sections of the Earth's crust that move
- Cryogenic Infrared Echelle Spectrometer:
- CRIRES: high resolution IR echelle spectrometer
- Cryovolcanism:
- Cryovolcano: eruption of substances that are liquid or gas at cold temperatures
- Cryovolcano: eruption of substances that are liquid or gas at cold temperatures
- Crystalline:
- Ice: solid state of water
- CS:
- Tracer: chemical whose presence indicates the presence of another chemical
- CSA: Canadian agency includes astronomical research
- CSHELL:
- IRTF: Mauna Kea 3-meter infrared telescope
- CSI:
- CSIRO:
- CSM:
- CSMF:
- CSN:
- CSO:
- CSS:
- CTA:
- CTIO:
- CTIO 1.5m:
- CTIO Schmidt Camera:
- CTIO Upper-Scorpius OB Association Survey (UScoCTIO): survey of low-mass stars and brown dwarfs
- CTX:
- Cubewano:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Curiosity:
- Mars: well-explored planet in the solar system
- Current Sheet: narrow sheet within a magnetic field where current flows
- Curtis-Shapley Debate:
- Great Debate: historical debate regarding the nature of galaxies
- Curvature: unflatness of space
- Curvature Fluctuation Amplitude:
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- Curvature Radiation: synchrotron-like radiation when particles follow curved field lines
- Curvature Sensor:
- Curve of Growth:
- CV:
- CvB:
- CVZ:
- CWFM:
- CWI:
- CXB:
- CXC:
- CXE:
- HEAO-1: 1977 x-ray observatory space mission
- CXO:
- Cycloalkane:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Cyclotron:
- Cyclotron Frequency:
- Cyclotron Radiation: radiation emitted when charged particles are accelerated
- Cygnus A (3C 405,QSO B1957+405): early-discovered radio galaxy and quasar
- Cygnus X Star Forming Region:
- Cylindrical Telescope: telescope with cylindrical reflectors
- Cz:
- Czernik:
- Czernik Catalog (Cz): list of open clusters
- Czernik Open Cluster Catalogue:
- D:
- CFHTLS: surveys of transients and stars
- Deuterium (D): hydrogen isotope with one neutron
- D Lines:
- Sodium (Na): metal, Na, atomic number 11
- D Orbital:
- D²:
- DEEP2: redshift survey of 60,000 galaxies
- D-σ Relation:
- D-Type Galaxy:
- D1:
- CFHTLS: surveys of transients and stars
- D2:
- CFHTLS: surveys of transients and stars
- D3:
- CFHTLS: surveys of transients and stars
- D4:
- CFHTLS: surveys of transients and stars
- dL:
- Luminosity Distance (dL, DL): distance to an object based upon the distance's effect on received flux
- DA:
- Dall-Kirkham Telescope: type of reflecting telescope
- Dalton (Da,u): mass unit used on atomic scale
- Daphnis:
- Darcy Velocity:
- Darcy Velocity Field: vector field indicating a kind of seepage in a porous medium
- Darcy's Law:
- Dark Age: interval when the universe's hydrogen atoms were neutral
- Dark Ages:
- Dark Age: interval when the universe's hydrogen atoms were neutral
- Dark Energy: energy theorized to accelerate the expansion of the universe
- Dark Energy Camera:
- Dark Energy Space Telescope:
- WFIRST: proposed space observatory
- Dark Energy Spectroscopic Instrument (DESI): planned instrument for measuring red-shift of distant objects
- Dark Energy Survey (DES): survey aimed at mapping the universe's expansion
- Dark Flow: non-random patterns in peculiar velocity of galaxy clusters
- Dark Halo:
- Dark Matter: matter hypothesized to provide galaxies with mass that can't be viewed
- Cold Dark Matter (CDM): one of three "dark matter" theories
- Cosmic Evolution Survey (COSMOS): investigation of dark matter and the universe's large scale structure
- Dark Matter Halo: hypothetical dark matter throughout and surrounding a galaxy
- Galactic Halo: spherical region around a galaxy with gas, dark matter, etc.
- Galaxy Bias: degree to which galaxy density fails to correspond to dark matter density
- Halo Abundance Matching (HAM): method of comparing observed galaxies with cosmology models
- Halo Mass Function: mass of distribution of dark matter
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- LasDamas: simulations of large scale evolution of dark matter and galaxies
- MACHO: proposed astronomical objects comprising dark matter
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- MOA: search for microlensing
- Navarro-Frenk-White Profile (NFW Profile): a dark matter spatial mass distribution function
- OGLE: survey searching for microlensing transients
- RHAPSODY: simulation of galaxy cluster dark-matter halos
- VIRMOS-VLT Deep Survey (VVDS): spectroscopic survey of 100,000 high-redshift galaxies
- WIMP: proposed particle comprising dark matter
- Dark Matter Halo: hypothetical dark matter throughout and surrounding a galaxy
- Dark Nebula:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Reflection Nebula: nebula made visible by light it scatters from nearby stars
- Dark Night Sky Paradox:
- Olbers' Paradox: argument using the dark of the sky regarding the nature of the universe
- dark sky:
- Darwin: past plan for space telescopes acting as an interferometer
- DASCH: project to digitize old astronomy plates
- data:
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- IRSA: archive center for infrared data from NASA missions
- LAMBDA: NASA archive center re CMB data
- Planet Hunters (PH): crowdsourcing website to identify galaxy types from surveys
- Position-Position-Velocity Space (PPV): 3d space using velocity as one of the three dimensions
- Virtual Observatory (VO): online database of astronomical data
- Data Cube:
- database:
- HITEMP: spectroscopic parameters for modeling gas optics
- HITRAN: spectroscopic parameters for modeling atmospheric optics
- NASA/IPAC Extragalactic Database (NED): a database of galaxies and other objects outside the Milky Way
- Daughter Nuclide:
- David Dunlap Observatory:
- David Dunlap Observatory Catalog (DDO): catalog of dwarf galaxies
- Day:
- Solar Time: time based upon the position of the Sun in the Earth's sky
- DB:
- DBSP:
- DCMF:
- DCT:
- DDO:
- de Broglie Frequency:
- de Broglie Wavelength: wavelength of a particle's matter wave
- de Broglie Waves:
- de Sitter Universe:
- de Vaucouleurs' Law:
- de Vaucouleurs' Profile: relation between elliptical galaxy surface brightness and distance from center
- Dead Zone: area within a disk where normal things don't happen
- DEBRA:
- Debris Disk: circumstellar disk of dust and debris around a star
- dec:
- Declination (dec): direction coordinate above/below celestial equator
- DECam:
- Deceleration parameter:
- Decimal Exponent:
- Dex: a number or factor's log base 10
- Decision Tree:
- Decision Tree Learning:
- Declination (dec): direction coordinate above/below celestial equator
- Decollimator:
- Deconvolution:
- Decoupling:
- Recombination: time when the universe's ionized hydrogen atoms neutralized
- Decretion Disk: disk around an astronomical body of its ejected material
- DEEP:
- DEEP2: redshift survey of 60,000 galaxies
- Deep Atmosphere Models:
- Deep CO2; Cycle:
- Deep Extragalactic Evolutionary Probe:
- DEEP2: redshift survey of 60,000 galaxies
- Deep Field (DF): survey field subject to lengthy observation to identify distant galaxies
- Deep Impact:
- EPOXI: mission using Deep Impact for further exploration
- Deep Impact Extended Investigation:
- EPOXI: mission using Deep Impact for further exploration
- Deep Lens Survey (DLS): investigating mass distribution of the universe
- Deep Near Infrared Survey of the Southern Sky:
- DENIS: 1990s southern sky survey of two near-infrared bands
- Deep Survey: survey using lengthy observation to identify distant galaxies
- Deep Water Cycle:
- DEEP-GSS:
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2 Redshift Survey:
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2 Survey:
- DEEP2: redshift survey of 60,000 galaxies
- Deferent:
- Epicycle: small circular motion around a large circular motion
- Deformable Mirror (DM): mirror that can be flexed for fine control
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- Degeneracy: general word meaning a violation of normal rules
- Degeneracy Pressure:
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Degeneracy Weight: number of quantum states with same energy level
- Degeneracy Weighting:
- degenerate dwarf:
- White Dwarf: stellar remnant of mostly electron-degenerate matter
- Degenerate Energy Levels:
- Degeneracy: general word meaning a violation of normal rules
- Degenerate Matter:
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Degenerate Perturbation Problem:
- Degenerate Star:
- Deimos:
- DEEP2: redshift survey of 60,000 galaxies
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Mars: well-explored planet in the solar system
- Moon: Earth's natural satellite
- Delensing:
- Delta Cephei:
- Dendrogram: diagram of a "tree", i.e., of a graph without cycles
- DENIS: 1990s southern sky survey of two near-infrared bands
- Dense Cloud:
- Dense Core: dense molecular cloud
- Dense Core Mass Function (DCMF,CMF): function describing range of masses of dense cores
- Dense Gas Survey of the Magellanic Clouds:
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- Density:
- Sound Speed: speed at which compression waves traverse a gas
- Density Fluctuations:
- Density Parameter:
- Density Scale Height:
- DES:
- Descending Node:
- DESI:
- Design Review:
- MDR/SRR: planning step for a NASA mission
- designation:
- Destiny:
- WFIRST: proposed space observatory
- Detached Binary:
- detection:
- Red Noise: noise tending toward lower frequencies
- Deuterium (D): hydrogen isotope with one neutron
- DeVeny Spectrograph:
- Dex: a number or factor's log base 10
- DF:
- Deep Field (DF): survey field subject to lengthy observation to identify distant galaxies
- DG Code:
- DG Method:
- DGL:
- DGP Gravity: alternative theory of gravity addressing "dark energy"
- DGP Model:
- DGP Gravity: alternative theory of gravity addressing "dark energy"
- diagram:
- diagrams:
- Isophote: line on a diagram indicating a level of brightness
- Diamond Planet:
- Carbon Planet: theoretical planet-type with more carbon than oxygen
- Dickel-Wendker-Bieritz Catalog (DWB): list of HII regions in the Cygnus X star forming region
- Dielectric: insulator that responds to an electric field
- Dielectric Material:
- Dielectric: insulator that responds to an electric field
- Dielectric Medium:
- Difference Equations:
- Differential Equation:
- differential equations:
- Differential Rotation:
- Differential Spectroscopy:
- Diffraction: effect of an obstacle on a wave
- Diffraction Grating:
- Diffraction Limited: telescope limited only by the laws of diffraction
- Diffractive Interstellar Scintillation (DISS): diffraction of star light by the ISM
- Diffuse Cloud:
- HI Region (HI): cloud of neutral atomic hydrogen
- HII Region (HII): cloud of partially-ionized atomic hydrogen
- Diffuse Extragalactic Background Light:
- Diffuse Galactic Light:
- Diffuse HI Cloud:
- HI Region (HI): cloud of neutral atomic hydrogen
- Diffusion: the spreading of particles toward an even distribution
- Diffusion Coefficient:
- Diffusion: the spreading of particles toward an even distribution
- Diffusion Equation:
- Diffusion: the spreading of particles toward an even distribution
- Diffusivity:
- Diffusion: the spreading of particles toward an even distribution
- Digital Access to a Sky Century @ Harvard:
- DASCH: project to digitize old astronomy plates
- Digital Image Stabilization:
- Digitized Sky Survey (DSS): digitization of Palomar and UK Schmidt plates
- Dilute Core:
- Metal: in astrophysics, any element more massive than helium
- Dione:
- Moon: Earth's natural satellite
- Saturn: second largest planet in the solar system
- Dipole:
- Dipole Magnetic Field:
- Dipole Tilt:
- Dirac Constant:
- DIRBE:
- Direct Imaging: detection/observation of exoplanets by taking pictures of it
- PALMS: survey to find exoplanets for direct imaging
- Discontinuous Galerkin Method: computational method for PDEs handling discontinuities
- Discontinuous Shock:
- Shock Wave: abrupt propagating disturbance in a fluid
- Discovery Channel:
- Discovery Channel Telescope (DCT): 4.3m telescope at Lowell Observatory, Arizona
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- Discovery Program:
- Enceladus Life Finder (ELF): mission to search for life on Saturn moon Enceladus
- NASA: includes space-based astronomy research
- Psyche: planned space mission to orbit an asteroid
- Discrete Fourier Transform:
- Discrete Ordinates Radiative Transfer:
- DISORT: simulation of radiative transfer in an atmosphere
- Discrete Random Variable:
- Discrete Spectrum:
- disk:
- Disk Galaxy:
- Disk Migration:
- Disk Wind:
- Jet: stream of matter from an astronomical body
- disks:
- DISORT: simulation of radiative transfer in an atmosphere
- Dispersion:
- Spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- Velocity Dispersion (σ): statistical dispersion of velocities of a group of objects
- DISS:
- Dissociation:
- Dissociation Front:
- distance:
- Distance Ambiguity:
- Distance Modulus (u): apparent magnitude minus absolute magnitude
- distributed:
- disturbance:
- Diurnal Libration:
- Libration: oscillating motion of orbiting bodies relative to each other
- Diurnal Motion:
- Divergence Theorem:
- Diviner:
- DIXI:
- EPOXI: mission using Deep Impact for further exploration
- DLS:
- DM:
- DMR:
- DoDz:
- DOGS:
- Doldrums:
- Dolidze-Dzimselejsvili Catalogue (DoDz): list of 11 open clusters
- Dolidze-Dzimselejsvili Open Clusters Catalogue:
- DOLoRes:
- Domain Wall:
- Dominion Observatory 10.03 MHz Source Catalog (DB): 1960s survey of northern-hemisphere radio sources
- Dominion Observatory 1420 MHz Source Catalog (DA): 1960s survey of northern-hemisphere radio sources
- Dominion Radio Astrophysical Observatory (DRAO): radio observatory in British Columbia, Canada
- Dominion Radio Astrophysical Observatory 10.03 MHz Telescope:
- Dominion Radio Astrophysical Observatory 25.6m Telescope:
- Doppler:
- Doppler Beaming:
- Doppler Boosting:
- Doppler Broadening: broadening of spectral lines due to velocities of the photon sources
- Doppler Effect:
- Doppler Shift: wave frequency difference due to relative velocity difference with source
- Doppler Shift: wave frequency difference due to relative velocity difference with source
- Double Bond:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Double Planet:
- Pluto: dwarf planet formerly listed as one of the nine planets
- Double Star:
- Double Transit: star showing transits of two bodies
- Double Transit System:
- Double-Line Spectroscopic Binary: spectroscopic binary star where a specific line shows up at two different wavelengths
- Double-Lined Spectroscopic Binary:
- Down:
- DPOSS:
- DQ Herculis Star:
- DQ Tau: young binary star system
- DraGMet:
- DraGNS:
- Dragon Design:
- DragonCam:
- Dragone Telescope: off-axis reflecting telescope type that preserves polarization
- Dragone-Design Telescope:
- Dragonfly: plan for Titan flying rover
- Drake Equation: estimate of advanced life in the Milky Way
- DraMS:
- DRAO:
- Dreyer:
- Drift Barrier:
- Drogue:
- Drogue Chute: parachute to slow something moving at high speed
- Drogue Chute: parachute to slow something moving at high speed
- Drogue Parachute:
- Drogue Chute: parachute to slow something moving at high speed
- Dropout: means of identifying distant galaxies
- Dry Ice:
- Ice: solid state of water
- DSFG:
- DSS:
- DST:
- Durchmusterung:
- Durham:
- dust:
- Dust Extinction:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Dust Particle:
- Cosmic Dust: cosmic dust is dust in space such as interstellar dust
- Dusty Star-Forming Galaxy:
- Duty cycle: percent of time when activity is recurring
- dwarf galaxies:
- Dwarf Galaxy: small galaxy with a few billion stars
- Dwarf Nova: flash of a cataclysmic variable star
- Dwarf Planet: round like a planet, only smaller
- Pluto: dwarf planet formerly listed as one of the nine planets
- Dwarf Star:
- DWB:
- Dwingaloo Radio Observatory:
- Dwingeloo:
- Dwingeloo Obscured Galaxy Survey (DOGS): radio survey of ZOA for 21cm lines indicating galaxies
- Dwingeloo Radio Observatory:
- Dynamic Instability:
- Dynamical Friction: drag produced by gravitational interaction with surrounding objects
- Dynamical Instability: situation where a perturbance makes itself larger
- dynamical systems:
- Chaos Theory: theory of systems highly sensitive to initial conditions
- Dynamical Timescale:
- Free-Fall Time: time it would take a body to collapse if unopposed
- Timescale (t,τ): general length of time something takes
- Dynamics:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Dyne:
- E:
- E ring:
- Enceladus: Saturn moon considered possible carrier of life
- E-ELT:
- E-mode:
- Polarization Modes: electric and magnetic aspects of the polarization of electromagnetic radiation
- E-THEMIS:
- e-VLBI:
- EAGLE: simulation of galaxy formation and evolution
- EAGLE Project:
- EAGLE: simulation of galaxy formation and evolution
- Early:
- Early Galaxies:
- First Galaxies: targeted highest red-shift galaxies showing little or no metal
- Early M Dwarf:
- M Dwarf: small, cool main-sequence star in stellar class M
- early universe:
- Early-Type Galaxy:
- Galaxy: gravitationally-bound group of stars
- Earth:
- Earth-sized VLBI: near-maximal Earth-based VLBI
- Earths:
- Earthshine: reflected and electromagnetic radiation from Earth
- EBHIS:
- EBL:
- eBOSS:
- Eccentricity (e): degree to which an orbit is non-circular
- DQ Tau: young binary star system
- ECDFS:
- Echelette Grating:
- Echelle Grating:
- Grating: spectrometer component
- HARPS: high-precision spectrograph for exoplanet searches
- Eclipse:
- Eclipse Mapping: using eclipse light curves to map surface features
- Eclipse Timing Offset:
- Eclipsing Binary: binary star system detected by variations in magnitude
- Ecliptic: path of the Sun on the celestial sphere as seen from Earth
- Ecliptic Coordinate System: celestial coordinate system system based upon Earth's orbital plane
- Ecliptic Latitude:
- Ecliptic Longitude:
- Ecliptic Plane Input Catalog:
- K2: second kepler mission working around failed equipment
- Eddington Accretion Rate:
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- Accretion Rate: rate of addition of mass to an object
- Eddington Luminosity: maximum luminosity at which radiation force overcomes gravity
- Eddington Approximation: approximation of a star's internal EMR's divergence from isotropic
- Eddington Bias: selection bias from mistaking something common for something rare
- Eddington Limit:
- Eddington Luminosity: maximum luminosity at which radiation force overcomes gravity
- Eddington-Barbier Relation:
- Source Function (S): measure indicating the effect of a material on EMR passing through
- Eddy:
- Edgeworth-Kuiper Belt:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Edgeworth-Kuiper Belt Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- EE Cosmic Rays:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- EECR:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- EECRs:
- Effective Radius (Re): radius of a galaxy within which 1/2 the light is emitted
- Effective Temperature (Teff): temperature of an equivalent black body in terms of total radiation
- Effelsberg Radio Telescope:
- EFI:
- THEMIS: set of satellites studying the Earth's magnetic field
- EFOSC2:
- EGO:
- EGRET:
- EGS:
- Eh:
- EHT:
- Eigen-Decomposition:
- Eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- Eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- Eigenmode Decomposition:
- Eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- Eigenmode Expansion:
- Eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- Eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- Eigenvector:
- Eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- Einstein Angle:
- Einstein Observatory:
- HEAO-2: 1978 x-ray observatory space mission
- Einstein Parallax:
- Einstein Radius:
- Einstein Ring:
- Einstein Telescope: concept for a larger LIGO-like GW detector
- Einstein's Field Equation:
- Einstein-de Sitter Model: universe tuned to the smallest expansion that continues forever
- Einstein-de Sitter Universe:
- Einstein-Rosen Bridge:
- Wormhole: connection between two regions in a curved space
- EIS:
- EIT:
- Ejection: forcing or throwing something out
- EKBO:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- El Niño:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Elastic Scattering:
- electricity:
- Electromagnetic Induction:
- Electromagnetic Radiation (EMR): radiation such as light, radio, x-rays
- Electromagnetic Spectrum: spectrum of EMR
- Electromagnetism (EM): electricity and magnetism and their interaction
- Electromotive Force (EMF): force that drives an electric current
- Electron:
- Electron Capture: combination of an electron with a proton
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Electron Degeneracy Pressure:
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Electron Degenerate Matter:
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Electron Excitation:
- Electron Neutrino:
- Electron Orbital: a nucleus's "locations" where an electron can orbit
- Electron Pressure:
- Electron Relaxation:
- Electron Scattering: any process that changes the course of an electron
- Electron Screening: reduction of effective charge of a nucleus by nearby electrons
- electronic:
- Electronic Very-long-baseline Interferometry (e-VLBI): real-time VLBI using electronic links
- electronics:
- Electrostatic Bond:
- Ice: solid state of water
- Electroweak: single conception including both electromagnetic and weak forces
- Electroweak Force:
- Electroweak: single conception including both electromagnetic and weak forces
- WIMP: proposed particle comprising dark matter
- Element:
- Calcium (Ca): element, Ca, atomic number 20
- Carbon (C): element, C, atomic number 6
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- Helium (He): non-metallic element, He, atomic number 2
- Hydrogen (H): most prominent element, atomic number 1
- Iron (Fe): metal, Fe, atomic number 26
- Lithium (Li): metal, Li, atomic number 3
- Nickel (Ni): metal, Ni, atomic number 28
- Nitrogen (N): metal, N, atomic number 7
- Oxygen (O): element, O, atomic number 8
- Silicon (Si): metal, Si, atomic number 14
- Sodium (Na): metal, Na, atomic number 11
- Sulfur (S): metal, S, atomic number 16
- Elevation Range: measure of how high and low a telescope can be pointed
- ELF:
- ELG:
- ELHC:
- Elias 2-27: much-studied YSO
- ELIRG:
- eLISA:
- Ellipse:
- elliptical:
- Elliptical Galaxies:
- Elliptical Galaxy: ellipsoidal-shaped galaxy
- Ellipticity:
- Elongation:
- ELT:
- EM:
- EM Radiation:
- Embryo:
- Embryo Barrier: a barrier to accretion on the order of the size of Pluto
- Emergent Gravity:
- EMF:
- EMIR:
- EMIR Multi-line Probe of the ISM Regulating Galaxy Evolution:
- Emission: addition of photons to a beam of EMR
- Emission Band:
- Emission Coefficient (j): measure of how much light a substance emits
- Emission Line: point of high intensity in a spectrum
- Emission Line Galaxy (ELG): a galaxy type characterized by emission lines
- Emission Spectroscopy:
- EMPIRE Survey: survey of gas in M51a to follow up PAWS
- EMR:
- 21cm Experiment: search for redshifted 21cm hydrogen emission lines
- AB System: monochromatic magnitude calibration based upon absolute values
- Absolute Magnitude (M): magnitude as seen from 10 parsecs
- Absorption: removal of photons from a beam of EMR
- Absorption Coefficient: measure of how much light a substance absorbs
- Active Galactic Nucleus (AGN): central region of a galaxy with extremely high luminosity
- Albedo: measure of reflectance
- Anomalous Cosmic Rays (ACR): cosmic rays with unexpectedly low energies
- Aperture: opening through which light passes
- Aperture Synthesis: interferometry to simulate a larger aperture telescope
- Apparent Magnitude (m): magnitude as seen from Earth adjusted for atmosphere
- Atmospheric Window: frequency bands in which the atmosphere passes electromagnetic radiation
- Aurora: light produced by atmosphere and solar wind
- B: photometric filter for blue light
- Bandwidth: number of Hertz between minimum and maximum frequencies
- Black Body (BB): idealized object that reflects no light
- Black-Body Radiation: continuous spectrum characteristic of the temperature of a body
- Bolometer: instrument measuring heat produced by radiation
- Bolometric Correction: difference between an object's bolometric and visible magnitudes
- Bolometric Luminosity: total luminosity of an object at all wavelengths
- Bolometric Magnitude (Mbol,Mbol): absolute magnitude of all wavelengths
- Bremsstrahlung: photon emission when a charged particle is decelerated
- Cherenkov Radiation: radiation from the shock of a charged particle passing through a medium
- Chirp: burst of signal rising or falling in frequency
- Circular Polarization Ratio (CPR): ratio of circular polarization handedness in reflected radar signal
- CMB Lensing: gravitational lensing of the CMB
- Color Index: a number that characterizes the color of an object
- Color-Color Diagram: means of comparing characteristics of stars
- Color-Period Diagram: means of comparing periods of stars at various wavelengths
- Column Density: measure of the matter through which EMR is passing
- Compton Scattering: photon collision with a charged particle that emits a different photon
- Continuum Emission: continuous spectrum such as black body radiation or bremsstrahlung
- Cooling Function: function relating a gas's cooling rate to its temperature
- Cosmic Background Radiation (CBR): electromagnetic radiation coming from every direction
- Cosmic Infrared Background (CIB): widespread infrared radiation not associated with known sources
- Cosmic Microwave Background (CMB): microwave radiation coming from every direction
- Cosmic Optical Background (COB): widespread optical radiation not associated with known sources
- Cosmic X-Ray Background (CXB): x-ray radiation coming from outside the Milky Way
- Cross Dispersion Spectrograph: echelle spectrograph with additional disperser crosswise to the first
- Curvature Radiation: synchrotron-like radiation when particles follow curved field lines
- Cyclotron Radiation: radiation emitted when charged particles are accelerated
- Distance Modulus (u): apparent magnitude minus absolute magnitude
- Doppler Broadening: broadening of spectral lines due to velocities of the photon sources
- Earth-sized VLBI: near-maximal Earth-based VLBI
- Earthshine: reflected and electromagnetic radiation from Earth
- Eddington Approximation: approximation of a star's internal EMR's divergence from isotropic
- Effective Temperature (Teff): temperature of an equivalent black body in terms of total radiation
- Electromagnetic Radiation (EMR): radiation such as light, radio, x-rays
- Electromagnetic Spectrum: spectrum of EMR
- Electronic Very-long-baseline Interferometry (e-VLBI): real-time VLBI using electronic links
- Emission: addition of photons to a beam of EMR
- Emission Coefficient (j): measure of how much light a substance emits
- Equation of Radiative Transfer (RTE): equation describing energy transfer by EMR
- Equilibrium Temperature (Teq,Teq): temperature a planet would have if it were an externally-heated black body
- European VLBI Network (EVN): consortium of radio telescopes to coordinate VLBI efforts
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Extragalactic Background Light (EBL): electromagnetic radiation from star formation and AGNs
- Extreme Ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10nm-124nm
- Extremely Low Frequency (ELF): electromagnetic radiation, frequency 3Hz to 30Hz
- Far Infrared (FIR): infrared radiation with wavelengths in the 30-450um range
- Fast Radio Burst (FRB): astronomical high energy radio pulses of a few milliseconds
- Flux: flow rate per unit area
- Frequency: number of cycles per unit of time, such as waves per second
- Frequency Modulation (FM): changing the frequency of a signal's carrier
- G Band: band of visible light around 5100 angstroms
- Galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- Gamma Rays: electromagnetic radiation, wavelength 10 picometers and less
- Gamma-Ray Burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Gravitational Lensing: focusing electromagnetic radiation by gravitational force
- Gravitational Microlensing: gravitational lensing by "small" objects such as individual stars and planets
- Gravitational Redshift: redshift due to GR effects of gravity
- Greenhouse Effect: mechanism that boosts temperature through selective blocking of EMR
- Gunn-Peterson Trough: spectral feature in EMR from redshift 6+
- GZK Limit: limit on energy of cosmic rays
- I Band: photometric filter for near infrared light
- Imaging Fourier Transform Spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
- Imaging Spectrometer: device to capture spectrum point-by-point of an image
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- Integral Field Spectrograph: spectrograph that captures images
- Integral Field Unit (IFU): instrument to allow a spectrograph to capture data over a 2d field
- Intensity: power reaching a surface from a specific source
- Intensity Mapping: measure of cosmic matter density
- Interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- Irradiance: power reaching a surface
- Jansky (Jy): unit of measurement of spectral flux density
- JHK Photometric System (JHK): system to classify stars according to near-infrared colors
- K Band: infrared passband centered around 2.2 microns, or 136 THz
- K Correction: correction to magnitude for redshift
- Kirchhoff's Laws: laws regarding the source of spectral lines
- Line Shape Function: function describing the shape of a spectral line
- Low-Surface-Brightness Galaxy (LSB Galaxy): galaxies less bright than those historically identified
- Luminosity (L): measure of brightness
- Lyman-Werner Photon: ultraviolet photon with proper energy to excite molecular hydrogen
- Magnetic Dipole Radiation: EMR naturally generated by a spinning magnetic dipole
- Magnitude: a logarithmic measure of brightness
- Maser: electromagnetic radiation amplified by stimulated emission
- Microwave: electromagnetic radiation, frequency 300MHz to 300GHz
- Mid Infrared (MIR): infrared radiation with wavelengths in the 7.5um-25um range
- Monochromatic Luminosity: luminosity at a specific wavelength
- Multi-Object Spectrograph: device to record the spectrum of multiple targets simultaneously
- Multipole Expansion: series expansion of a function over the surface of a sphere
- Near Infrared (NIR,Near-IR): electromagnetic radiation in the range of 800-2500 nm
- OIR: a spectral "band name" for both visible light and infrared
- Opacity: a measure of opaqueness of a material
- Optical Depth (τ): a measure of opaqueness of a path of light
- Passband: range of electromagnetic wavelengths that a filter allows
- Phase Curve: brightness of an object according to its phase angle
- Photoevaporation: dispersal of a gas from UV radiation
- Photometer: instrument measuring brightness
- Photometric Redshift: method of estimating redshift without spectroscopy
- Photometric System: specification of a set of filters/passbands
- Photon Noise: variation in light measurement due to its quantum nature
- Planck Function: yields black body curve
- Polarimetry: measurement of polarization of EMR
- Polarization: property of waves that oscillate in a particular direction
- Polarization Modes: electric and magnetic aspects of the polarization of electromagnetic radiation
- Poynting Vector (S): measures directional energy flux density
- Quenched Galaxy: galaxy currently producing minimal stars
- R Band: band of visible light around 6500 angstroms
- Radar: probe based on reflecting radio waves
- Radiance: measure of EMR to/from a solid angle through and area
- Radiant Flux: measure of brightness
- Radiation Hydrodynamics (RHD): hydrodynamics plus the affects of EMR
- Radiation Pressure: the pressure exerted by electromagnetic radiation
- Radiative Flux: power passing through a unit area
- Radiative Transfer (RT): energy transfer in the form of electromagnetic radiation
- Radiative Transfer Code (RT Code): computer model of a gas's radiative transfer
- Radiative Transfer Model (RTM): models of radiative transfer, often computerized
- Radio: electromagnetic radiation, frequency 3kHz to 300GHz
- Radiometer: device for measuring radiant flux
- Reddening: red appearance of astronomical objects because blue light is attenuated by dust
- Redshift (z): change to longer wavelengths due to Doppler affects
- Redshift Space: map of space using redshift as the radial dimension
- Relativistic Beaming: directional relativistic effect on light from relativistic speeds
- Relativistic Speed: a good fraction of the speed of light
- Rest Wavelength: normal wavelength observed when not moving in relation to the source
- Schuster-Schwarzschild Model: approximation of a star's internal EMR's divergence from isotropic
- Sensitivity Function (S): function of wavelength giving the sensitivity of an instrument
- Solar Constant: flux from the Sun at 1 AU
- Source Function (S): measure indicating the effect of a material on EMR passing through
- Spectral Energy Distribution (SED): function or plot of brightness at each wavelength in the spectrum
- Spectral Flux Density (S): flux or power of radiation per unit area per unit wavelength
- Spectral Index (α): power by which an object's flux depends on frequency
- Spectral Line Energy Distribution (SLED): function or plot of brightness of lines in a spectrum
- Spectral Resolution (R): measure of a spectrograph's ability to resolve features of the spectrum
- Spectrograph: device to record the spectrum of incoming light
- Spectrography: charting the strengths of different electromagnetic wavelengths
- Spectrometer: device to measure light by wavelength across its spectrum
- Spectrometry: measuring the strengths of different electromagnetic wavelengths
- Spectroscope: device to study the spectrum of incoming light
- Spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- Starburst Galaxy: galaxy forming stars at a very high rate
- Stokes Parameters: way to describe polarization state
- Strömgren Photometric System: four-color photometric system devised in 1950s
- Submillimeter Galaxy (SMG): galaxy that produces significant submillimeter radiation
- Subradio: electromagnetic radiation, frequency below 3kHz
- Super Low Frequency (SLF): electromagnetic radiation, frequency 30Hz to 300Hz
- Surface Brightness: brightness per unit area of a surface
- Synchrotron Radiation: radiation emitted when high-speed charged particles are accelerated
- Synchrotron Self-Compton (SSC): charged particle cloud scattering its own synchrotron-produced photons
- Thomson Optical Depth: a measure of affects of Thomson scattering
- Transit Spectroscopy: spectroscopy through an exoplanet's transit
- Transmission Spectroscopy: spectrum of radiation passing through a substance
- Tremendously Low Frequency (TLF): electromagnetic radiation, frequency below 3Hz
- Two-stream Approximation: approximation of a star's internal EMR's divergence from isotropic
- U: photometric filter for ultraviolet light
- UBV Photometric System: commonly-cited photometric system for describing stars' colors
- Ultra Low Frequency (ULF): electromagnetic radiation, frequency 300Hz to 3kHz
- Ultra-High-Energy Gamma Rays (UHEGR): energetic gamma rays with more than 100 TeV photon energy
- Ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- V: photometric filter for visible light
- Vega System: magnitude calibration such that Vega has zero magnitude
- Very Low Frequency (VLF): electromagnetic radiation, frequency 3kHz to 30kHz
- Very-High-Energy Gamma Rays (VHEGR): energetic gamma rays with 100 GeV to 100 TeV photon energy
- Very-long-baseline Interferometry (VLBI): interferometry based upon storing timing data at each telescope
- Visible Light: electromagnetic radiation, wavelength 390-750 nm
- Wavelength: an alternative description of an electromagnetic wave's frequency or photon energy
- Weak Lensing: slight lensing detected in random patterns of distant objects
- Wien's Displacement Law: temperature times wavelength with maximum intensity equals a constant
- X-ray: electromagnetic radiation, wavelength .01 to 10 nanometers
- XEUV: electromagnetic radiation in the range of .15nm-400nm
- Zeeman-Doppler Imaging (ZDI): technique for imaging stellar magnetic fields
- EMU:
- ENA:
- Enceladus: Saturn moon considered possible carrier of life
- Enceladus Life Finder (ELF): mission to search for life on Saturn moon Enceladus
- Endothermic Reaction: reaction that absorbs heat
- Energetic Neutral Atom (ENA): high-speed neutral atom
- energy:
- Energy Density: energy per unit volume at a point in a field
- Energy Spectral Density:
- engineering:
- England:
- Entropic Gravity:
- Entropy:
- Envelope:
- Enzo: hydrodynamic simulation system
- EOR:
- EoS:
- EPAM:
- EPIC:
- EPICS:
- Epicycle: small circular motion around a large circular motion
- Epicyclic Frequency: frequency of oscillation in an accretion disk
- Epicycle: small circular motion around a large circular motion
- EPOCh:
- Epoch: time on which to base celestial coordinates
- EPOXI: mission using Deep Impact for further exploration
- Epoch J2000.0: noon 1/1/2000 GMT as used as a time reference
- Epoch of Galaxy Assembly:
- Epoch of Galaxy Formation: before z=1, when many galaxies formed
- Epoch of Reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- EPOXI: mission using Deep Impact for further exploration
- EPS Merger Trees:
- Epsilon Eridani: third nearest visible star system in sky
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- EPTA:
- Equant:
- Epicycle: small circular motion around a large circular motion
- equation:
- Equation of Radiative Transfer (RTE): equation describing energy transfer by EMR
- Equation of State (EoS): equation relating temperature, pressure, and volume
- Equation of State: Supernovae trace Cosmic Expansion:
- ESSENCE: survey using supernova data to study dark energy
- equatorial:
- Equatorial Coordinate System: latitude/longitude-like system for the celestial sphere
- Equatorial Kelvin Wave:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Equatorial Mount: telescope mount with axis parallel to Earth's
- Equatorial Rossby Wave:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Equatorial Wave:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Equilibrium Condensation Model: chemical model explaining solar system planet abundances
- Equilibrium Temperature (Teq,Teq): temperature a planet would have if it were an externally-heated black body
- Equinox: times when tilt of Earth is neither toward or away from the Sun
- equipment:
- Drogue Chute: parachute to slow something moving at high speed
- Filter: optical device to filter out part of the EMR spectrum
- Mirror Support Cell: units in a telescope that support the mirror
- MMRTG: power source for space probes
- Equivalent Width:
- Era of Reionization:
- Erg: CGS unit of energy
- Ergosphere:
- Black Hole (BH): region of such high mass that light cannot escape
- Eridanus Supervoid:
- Void: empty spaces between large scale structures
- Eridanus Void:
- Eris:
- ERNE:
- EROS: search for MACHOs
- EROS-1:
- EROS-2:
- Erosion:
- Ablation: erosion of the surface of an object
- Weathering: changes in surface due to contact with atmosphere
- Erosion Barrier:
- eROSITA: space x-ray telescope
- Error Bar: feature of a graph to indicate accuracy
- ESA:
- Escape Fraction: fraction of ionizing photons escaping a body
- Escape Velocity:
- ESD:
- ESO:
- ESO (B) Atlas:
- ESO 137-001: barred spiral galaxy in the Abell 3627 cluster
- ESO 3.6 Meter Telescope:
- HARPS: high-precision spectrograph for exoplanet searches
- ESO 97-G13:
- ESO Quick Blue Survey:
- ESO Schmidt Camera:
- ESO Schmidt Telescope:
- ESO VLT:
- ESO/Uppsala Survey Of The ESO (B) Atlas: 1970s southern all-sky survey
- ESO594-G004:
- ESPaDOnS:
- ESPRESSO:
- ESSENCE: survey using supernova data to study dark energy
- Eta Carinae:
- ETG:
- Galaxy: gravitationally-bound group of stars
- Ethane:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Ethene:
- Ethylene (C2H4): compound of two carbon and four hydrogen atoms
- Ether:
- Relativity: physics models accommodating the constancy of the speed of light
- Ethylene (C2H4): compound of two carbon and four hydrogen atoms
- Ethyne:
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- ETNO:
- Euclid: planned observatory-satellite to measure dark energy
- Eulerian Code:
- Eunomia:
- Europa: well-known Jupiter moon
- Europa Clipper: planned Europa space probe
- Europa Multiple Flyby Mission:
- Europe:
- European:
- European Extremely Large Telescope (E-ELT,ELT): 39-meter telescope under construction
- European Gravitational Observatory (EGO): gravitational wave observatory in Italy
- European Pulsar Timing Array (EPTA): European collaboration of radio telescopes
- European Southern Observatory (ESO): organization operating telescopes in the southern hemisphere
- European Southern Observatory Very Large Telescope (ESO VLT,VLT): four 8.2-meter optical telescopes in Chile that can act together
- European Space Agency (ESA): NASA-like international space organization in Europe
- European VLBI Network (EVN): consortium of radio telescopes to coordinate VLBI efforts
- Europium:
- EUV:
- EUVE:
- evaluation:
- EVE:
- event:
- 1947 Sunspot: largest sunspot ever recorded
- 775 AD Event: apparent solar eruption, based upon tree-ring evidence
- Big Bang: theoretical event when the universe expanded from a point
- Carrington Event: solar storm September 1-3 1859
- Cassiopeia A: supernova remnant visible for 300 years
- Epoch of Reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- Great Debate: historical debate regarding the nature of galaxies
- Late Heavy Bombardment (LHB): time after solar system planet-formation when many impacts occurred
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Recombination: time when the universe's ionized hydrogen atoms neutralized
- SN 1987A (1987A): rare supernova in February 1987 visible by the naked eye
- SN 2014J: type Ia supernova in Messier 82, the Cigar Galaxy
- Event Horizon:
- Event Horizon Telescope (EHT): growing VLBI network
- event type:
- EVN:
- Evolution and Assembly of Galaxies and their Environments:
- EAGLE: simulation of galaxy formation and evolution
- Evolutionary Map of the Universe:
- ExaFLOP:
- ExAO:
- Exascale Computing: exaFLOP computing capability, i.e., quintillion FLOPs
- Excitation:
- Excitation Temperature:
- Excited State:
- Exit Pupil: size of the image as presented to the eye
- Exo-C:
- Exo-S: a study on the concept of a starshade mission
- Exo-earth:
- Exo-S: a study on the concept of a starshade mission
- Exo-Starshade:
- Exo-S: a study on the concept of a starshade mission
- ExoCTK: collection of software for exoplanet observation and analysis
- Exoearth: Earth-like exoplanet
- ExoMars:
- Mars: well-explored planet in the solar system
- Exomoon:
- Exoplanet:
- Exoplanet Characterization Toolkit:
- ExoCTK: collection of software for exoplanet observation and analysis
- Exoplanet Eclipse Light Curve: graph of light as an exoplanet transits in front of its star
- Exoplanet Starshade:
- Exo-S: a study on the concept of a starshade mission
- Starshade: spacecraft to block light from a specific body
- exoplanets:
- Exosatellite: natural satellite not in the solar system
- Exosphere: outer portion of atmosphere
- Expérience pour la Recherche d'Objets Sombres:
- Expansion Fan: the "sound" of a supersonic flow flowing around a convex corner
- experiment:
- Gravity Sounding: measuring a planet's gravitation field by study of nearby probe flights
- Explorer 42:
- Uhuru: 1970 satellite x-ray telescope
- Explorer 80:
- Explorers Program:
- Extended Chandra Deep Field-South Survey (ECDFS): 1100 square arcminute x-ray survey
- Extended Groth Strip (EGS): region of sky searched for distant galaxies
- Extended Roentgen Survey with an Imaging Telescope Array:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Extinction Coefficient:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Extinction Curve:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Extinction Event:
- Extra-Solar Planet: planet not in the solar system
- Extragalactic Background Light (EBL): electromagnetic radiation from star formation and AGNs
- Extragalactic Distance Scale:
- Extrasolar Moon:
- Extrasolar Planet Observation and Deep Impact Extended Investigation:
- EPOXI: mission using Deep Impact for further exploration
- Extrasolar Satellite:
- Extreme Adaptive Optics (ExAO): high-performance version of AO system
- Extreme Energy Cosmic Rays:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- Extreme Kuiper Belt Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Extreme Luminous Supergiant:
- Extreme Trans-Neptune Object:
- Extreme Trans-Neptunian Object:
- Extreme Ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10nm-124nm
- Extreme Ultraviolet Explorer (EUVE): 1990s ultraviolet space telescope
- Extreme-Energy Cosmic Rays:
- Extremely Large Telescope (ELT): optical telescope with a 20+ meter aperture
- Extremely Low Frequency (ELF): electromagnetic radiation, frequency 3Hz to 30Hz
- Extremely Luminous Infrared Galaxy:
- Extrinsic S-Star:
- S-Type Star: type of star with lines indicating zirconium
- Eye Piece:
- Exit Pupil: size of the image as presented to the eye
- Eye Relief:
- Exit Pupil: size of the image as presented to the eye
- F:
- F-Type Star (F): type of star with about 1.5 times the mass of the Sun
- F Orbital:
- F-Class:
- F-Type Star (F): type of star with about 1.5 times the mass of the Sun
- f-mode:
- F-number:
- F-stop:
- F-Type Star (F): type of star with about 1.5 times the mass of the Sun
- f-value:
- fsky:
- Fsky (fsky): fraction of the sky, e.g. what a survey covers
- Faber-Jackson Relation: relation between elliptical galaxy luminosity and stellar velocity dispersion
- Faint Images of Radio Sky at Twenty Centimeters:
- USS Sources: catalog of sources with steep spectral index
- Faint Images of the Radio Sky at Twenty-Centimeters:
- FIRST: 1990s radio survey
- Faint Infrared Grism Survey (FIGS): survey to identify redshift of distant galaxies
- Fairall:
- Fairall Galaxy List (Frl,Fairall): 1977 list of galaxies with bright nuclei
- Fallback Supernova:
- False Vacuum: apparent QM vacuum
- Fanaroff-Riley Classification: a classification of the radio characteristics of radio sources
- Far Infrared (FIR): infrared radiation with wavelengths in the 30-450um range
- Far Infrared and Submillimetre Telescope:
- Far Ultraviolet:
- Far Ultraviolet Spectroscopic Explorer (FUSE): early 2000s space telescope for short-wavelength ultraviolet
- Far-Infrared Astronomy:
- Far Infrared (FIR): infrared radiation with wavelengths in the 30-450um range
- Faraday Effect:
- Faraday Rotation: rotation of optical polarization by a medium in a magnetic field
- Faraday Rotation: rotation of optical polarization by a medium in a magnetic field
- FAST: Arecibo-like 500m telescope in deployment in China
- Fast Fourier Transform (FFT): efficient algorithm for calculating a discrete Fourier transform
- Fast Fourier Transform Telescope: proposed all-digital telescope with synthetic aperture
- Fast Infrared Exoplanet Spectroscopy Survey Explorer:
- FINESSE: planned space mission for exoplanet spectrography
- Fast Radio Burst (FRB): astronomical high energy radio pulses of a few milliseconds
- Fast Shock:
- Shock Wave: abrupt propagating disturbance in a fluid
- FDM:
- Fe:
- Iron (Fe): metal, Fe, atomic number 26
- FEA:
- Feedback:
- Feedback in Realistic Environments:
- Feldspar:
- Basalt: an igneous rock type that shows rapid cooling
- FEM:
- Fenton Hill Observatory:
- Milagro: gamma ray telescope using Cherenkov radiation
- RAPTOR: automated array of telescopes to uncover and track transients
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Fermi Energy:
- Electron Degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- Fermi Gamma-Ray Space Telescope:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Fermi-Dirac Distribution:
- Fermi-Dirac Statistics:
- Fermion:
- Fermion Ray:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- Fermionic Ray:
- Cosmic Rays (CR): very-high-energy particles from beyond the solar system
- Ferrel Cell:
- Hadley Cell: circulation pattern of up at the equator, out, down, and back
- Ferromagnetism:
- FFT:
- FFT Telescope:
- FGK Star: a star of class F, G, or K
- FGM:
- THEMIS: set of satellites studying the Earth's magnetic field
- FGS:
- FGST:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Fick's Laws:
- Diffusion: the spreading of particles toward an even distribution
- Fickian Diffusion:
- Diffusion: the spreading of particles toward an even distribution
- Field:
- Field of View (FOV): angular measure of how much an optical instrument can view
- Field of Vision:
- Field of View (FOV): angular measure of how much an optical instrument can view
- Field Spectrometer:
- Spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- FIGS:
- Filament: linear volume of high molecular gas density within a galaxy
- Nessie: star forming filament found in the Orion star forming region
- Filled Ice:
- Clathrate: crystal lattice with voids that can trap molecules
- Filter: optical device to filter out part of the EMR spectrum
- B: photometric filter for blue light
- G Band: band of visible light around 5100 angstroms
- I Band: photometric filter for near infrared light
- Passband: range of electromagnetic wavelengths that a filter allows
- R Band: band of visible light around 6500 angstroms
- U: photometric filter for ultraviolet light
- V: photometric filter for visible light
- filters:
- Final Parsec Problem: lack of a convincing theory on how SMBHs can reach each other
- Fine Structure: spectral lines due to electron spin and relativistic effects
- Fine Structure Constant:
- Fine Structure: spectral lines due to electron spin and relativistic effects
- FINESSE: planned space mission for exoplanet spectrography
- Finger of God Distortion:
- Finite Difference Method (FDM): means of estimating calculus and differential equation solutions
- Finite Element Analysis:
- Finite Element Method (FEM,FEA): computational method for PDEs suited to physical problems
- Finite Volume Method (FVM): computational method to PDEs especially suited to fluid dynamics
- Finite-Volume Method:
- MITgcm: well-known general circulation model
- FIR:
- Far Infrared (FIR): infrared radiation with wavelengths in the 30-450um range
- FIRAS:
- FIRE:
- FIRE Simulations: high resolution simulation of galaxies
- FIRST: 1990s radio survey
- First Galaxies: targeted highest red-shift galaxies showing little or no metal
- First Light: initial demonstration that a telescope works
- First Order Perturbation Problem:
- First Point of Aries:
- Equinox: times when tilt of Earth is neither toward or away from the Sun
- FIS:
- AKARI: Japanese space infrared telescope
- Fission:
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- Quantum Number: number representing a conserved quantity
- FITS:
- SPECTRE: an interactive spectrum analysis software package
- Five Hundred Meter Aperture Spherical Telescope:
- FAST: Arecibo-like 500m telescope in deployment in China
- Flagship Missions:
- NASA: includes space-based astronomy research
- FLAMES:
- Flamsteed Designation: star designation system dating from 1700s
- FLAO:
- Flare Spray:
- Flare Star:
- Flaring State:
- FLASH: hydrodynamic simulation system
- Flash Center For Computational Science:
- FLASH: hydrodynamic simulation system
- Flat Universe:
- Flatness Problem:
- Inflation: theorized rapid expansion of the very early universe
- Flexible Image Transport System:
- SPECTRE: an interactive spectrum analysis software package
- Flexible Modeling System:
- TAM: non-gray-RT 3D model of Titan's atmosphere
- FLITECAM:
- SOFIA: aircraft-based infrared observatory
- Flora:
- Fluence:
- Flux: flow rate per unit area
- Fluffy CAI:
- CAI: calcium/aluminum specs in chondrites
- fluid dynamics:
- fluid mechanics:
- Fluorescence:
- Fluorescence Protection:
- Biofluorescence: common fluorescence in organisms to dissipate harmful UV radiation
- Fluorescent Protein:
- Biofluorescence: common fluorescence in organisms to dissipate harmful UV radiation
- Fluoride:
- Geochemistry: the chemistry of the Earth, planets, and moons
- Fluorine:
- Geochemistry: the chemistry of the Earth, planets, and moons
- Flux: flow rate per unit area
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- PCA Analysis: an automatable method of determining galaxy morphology
- Solar Constant: flux from the Sun at 1 AU
- Spectral Flux Density (S): flux or power of radiation per unit area per unit wavelength
- Flux Density:
- Flux Reconstruction (FR): numerical approach emphasizing joining the subdivisions
- Flux Rope: rope-shaped structure in magnetic fields associated with coronal mass ejections
- FLWO:
- FM:
- FMOS:
- FMS:
- TAM: non-gray-RT 3D model of Titan's atmosphere
- FOC:
- Focal Length: length from optical element to focal plane
- Focal Plane: plane within optical system at which an image is in focus
- Focal Plane Array (FPA): array of receivers at the focus of a radio telescope
- Focal Point:
- Focal Plane: plane within optical system at which an image is in focus
- Focal Ratio:
- Focal Length: length from optical element to focal plane
- Focal Plane: plane within optical system at which an image is in focus
- FOCAS:
- Focus:
- Focal Plane: plane within optical system at which an image is in focus
- Foe: unit of energy on the order of a supernova's output
- Fokker-Planck Equation: shows likelihood of velocity over time of a disturbed particle
- Forbidden Line: lines that quantum mechanics disallows for the most part
- Forbidden Mechanism:
- Forbidden Line: lines that quantum mechanics disallows for the most part
- Forbidden Transition:
- Forbidden Line: lines that quantum mechanics disallows for the most part
- FORCAST:
- SOFIA: aircraft-based infrared observatory
- Forced Libration:
- Enceladus: Saturn moon considered possible carrier of life
- Libration: oscillating motion of orbiting bodies relative to each other
- FORNAX: hydrodynamics simulation software
- Fornax Cluster:
- Fornax Wall:
- FORS2:
- Forward Model: model producing potential observable values from parameters
- FOS:
- Four-body Problem:
- N-Body Problem: predicting the paths of celestial objects with gravitation interaction
- Four-Shooter:
- Fourier Analysis:
- Linear Theory: theory of operators satisfying the property of superposition
- Fourier Domain:
- Fourier Space: domain into which the Fourier transform maps a function
- Fourier Series:
- Fourier Series Expansion:
- Fourier Space: domain into which the Fourier transform maps a function
- Fourier Transform: systematic method of breaking down functions into periodic components
- FourStar:
- Fourth Cambridge Catalog of Radio Sources (4C): 1960s catalog of northern hemisphere 178MHz sources
- Fourth Cambridge Survey:
- FOV:
- Field of View (FOV): angular measure of how much an optical instrument can view
- FPA:
- FPCS:
- HEAO-2: 1978 x-ray observatory space mission
- FR:
- FR Classification:
- FR-I:
- FR-II:
- Fraction Of The Sky:
- Fsky (fsky): fraction of the sky, e.g. what a survey covers
- Fractionation: separation of compounds from a mixture
- Fractionation Factor: isotope quantity
- Fragmentation Barrier:
- Frame Dragging:
- Black Hole (BH): region of such high mass that light cannot escape
- Frame Of Reference: possibly moving region from which something is observed/considered
- Reduced Mass: the reciprocal of the sum of the reciprocals of the masses of two objects
- Relativity: physics models accommodating the constancy of the speed of light
- France:
- Frank Ross's Catalog: high-proper-motion and variable stars catalogued by Frank Ross
- Frank Ross's List:
- Fraunhofer Diffraction:
- Fraunhofer Lines:
- G Band: band of visible light around 5100 angstroms
- Fraunhofer's G Band:
- G Band: band of visible light around 5100 angstroms
- FRB:
- Fast Radio Burst (FRB): astronomical high energy radio pulses of a few milliseconds
- FRB 121102:
- Fast Radio Burst (FRB): astronomical high energy radio pulses of a few milliseconds
- Fred Lawrence Whipple Observatory (FLWO): observatory near Amado, Arizona
- IOTA: optical interferometer
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Frederick C. Gillett Gemini Telescope:
- Free Electron:
- Free-Bound Emission:
- Recombination: time when the universe's ionized hydrogen atoms neutralized
- Free-Fall Time: time it would take a body to collapse if unopposed
- Free-Fall Timescale:
- Free-Fall Time: time it would take a body to collapse if unopposed
- Timescale (t,τ): general length of time something takes
- Free-Free:
- Free-Free Absorption:
- Bremsstrahlung: photon emission when a charged particle is decelerated
- Free-Free Radiation:
- Bremsstrahlung: photon emission when a charged particle is decelerated
- Freeman Law:
- Freeman's Law: all spiral galaxy's have the same central surface brightness
- Freeman's Law: all spiral galaxy's have the same central surface brightness
- Frequency: number of cycles per unit of time, such as waves per second
- Frequency Domain:
- Fourier Space: domain into which the Fourier transform maps a function
- Frequency Modulation (FM): changing the frequency of a signal's carrier
- Frequentist Statistics:
- Fresnel Diffraction:
- Fried parameter:
- Seeing: apparent blurring and twinkling of objects seen through atmosphere
- Friedmann Equation:
- Friedmann Model:
- Friedmann Universe:
- Frl:
- Front End Instrument: instruments of a telescope that detect and encode the signal
- Frost Line:
- Snow Line: distance from protostar cool enough for water to condense
- Fsky (fsky): fraction of the sky, e.g. what a survey covers
- FSPS:
- FU Orionis Star:
- Full Width At Half Maximum (FWHM): a measure of the width of a hump-shaped curve
- function:
- Function Space:
- Basis Function: one of a set of functions used to approximate a function of interest
- Fundamental Plane: three-way relation between elliptical galaxy characteristics
- Funnelweb Survey:
- TAIPAN: multi-object spectrograph with robot fiber-positioner
- FUor:
- FUSE:
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- FUV:
- Ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- FVM:
- Finite Volume Method (FVM): computational method to PDEs especially suited to fluid dynamics
- MITgcm: well-known general circulation model
- FWHM:
- G:
- G-Type Star (G): stars similar to the Sun
- Gauss (G,Gs): measurement of magnetic field β
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- Glycine (Gly,G): smallest of the twenty common amino acids
- G 268-38:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- G 270-58:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- G Band: band of visible light around 5100 angstroms
- G-Class:
- G-Class Star:
- G-CLEF: spectrograph on the GMT
- G-Dwarf:
- G-Dwarf Problem: lack of metal-poor G-Dwarfs in the Milky Way
- g-mode:
- G-Type Star (G): stars similar to the Sun
- G395:
- Gadget:
- Gadget-2: an n-body/SPH simulation computer program
- Gadget-1:
- Gadget-2: an n-body/SPH simulation computer program
- Gadget-2: an n-body/SPH simulation computer program
- Gaia: survey satellite at 400-1000 nanometers
- Gaia Data Release 1:
- Gaia: survey satellite at 400-1000 nanometers
- Gaia Data Release 2:
- Gaia: survey satellite at 400-1000 nanometers
- Gaia DR1:
- Gaia: survey satellite at 400-1000 nanometers
- Gaia DR2:
- Gaia: survey satellite at 400-1000 nanometers
- Gaia-ESO Survey:
- Gaia: survey satellite at 400-1000 nanometers
- GALA:
- JUICE: mission to Jupiter in development
- Galactic All-Sky Survey (GASS): HI survey of the Milky Way
- Galactic Archaeology with HERMES:
- GALAH: survey of Milky Way with an emphasis on old structures
- Galactic Binary: system of two object co-orbiting in the Milky Way
- Galactic Bulge:
- Bulge: denser group of stars within a larger group
- Galactic Center: region at the middle of the Milky Way
- MicroFUN: observers following up on microlensing events in the galactic bulge
- Galactic Center: region at the middle of the Milky Way
- Galactic Cluster:
- Galaxy Cluster (CL): large group of galaxies gravitationally-bound to the group
- Open Cluster: group of stars within a galaxy apparently formed by a single cloud
- Galactic Coordinate System: celestial coordinate system system based upon the galactic plane
- Galactic Core:
- Galactic Corona:
- Corona: plasma surrounding a star
- Galactic Halo: spherical region around a galaxy with gas, dark matter, etc.
- Galactic Electron Density: density of electrons in the ISM
- Galactic Equator:
- galactic habitable zone:
- Galactic Halo: spherical region around a galaxy with gas, dark matter, etc.
- Galactic Latitude:
- Galactic Longitude:
- Galactic Main Sequence:
- Galactic Nucleus:
- Galactic Plane: plane in which the stars of the Milky Way reside
- Galactic Plane Infrared Polarization Survey:
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Galactic Poles:
- Galactic Spheroid:
- Galactic Halo: spherical region around a galaxy with gas, dark matter, etc.
- Galactic Stellar Nucleus:
- GALAH: survey of Milky Way with an emphasis on old structures
- Galatea:
- galaxies:
- 2dF Galaxy Redshift Survey (2dFGRS): imaging survey of 300,000 objects
- 3D-HST: near-infrared survey of 100,000 galaxies by HST
- Active Galactic Nucleus (AGN): central region of a galaxy with extremely high luminosity
- AEGIS: survey study of distant galaxies
- ALFALFA: HI survey of many galaxies
- APM Galaxy Survey (APMUKS): 1990s survey of galaxies in southern sky
- Arakelian Catalog (Ark): 1970s list of small/bright galaxies
- Arp-Madore Catalog of Southern Peculiar Galaxies (AM): 1970s-1980s catalog from the UK Schmidt Survey
- Asiago Supernova Catalog (B/SN): 1999 catalog of known supernovae and their galaxies
- Atlas 3d: survey of local galaxies
- Atlas of Peculiar Galaxies (APG): 1960s catalog-book with photos
- Bar: feature of some spiral galaxies
- BDF: field used in search for distant galaxies
- BigBOSS: BOSS survey follow-on
- Bulge: denser group of stars within a larger group
- Caldwell Catalog: small catalog for amateur astronomers as an adjunct to the Messier Catalog
- CALIFA: spectroscopic map of 600 galaxies
- CARMA EDGE: CO survey of galaxies
- Catalog Of Galaxies And Clusters Of Galaxies (CGCG): list of galaxies/clusters assembled in 1960s
- Catalogue of Interacting Galaxies (VV): begun in the 1950s
- CFHTLS: surveys of transients and stars
- Chandra Deep Field South (CDFS,CDF-S): highly-detailed X-ray image of small region of the sky taken by Chandra
- Circumgalactic Medium (CGM): gas surrounding a galaxy
- Cold Gas: gas cool enough to form galaxies and stars
- COLD GASS: survey of CO in nearby large galaxies
- Color-Magnitude Diagram (CMD): diagram relating color to luminosity
- Conditional Luminosity Function (CLF): function characterizing luminosity of galaxies with a given halo mass
- Conditional Stellar Mass Function (CSMF): function characterizing galaxies within a halo of a given mass
- Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS): early universe survey by HST
- Dark Matter: matter hypothesized to provide galaxies with mass that can't be viewed
- Dark Matter Halo: hypothetical dark matter throughout and surrounding a galaxy
- David Dunlap Observatory Catalog (DDO): catalog of dwarf galaxies
- de Vaucouleurs' Profile: relation between elliptical galaxy surface brightness and distance from center
- Deep Field (DF): survey field subject to lengthy observation to identify distant galaxies
- Deep Lens Survey (DLS): investigating mass distribution of the universe
- Deep Survey: survey using lengthy observation to identify distant galaxies
- DEEP2: redshift survey of 60,000 galaxies
- Dropout: means of identifying distant galaxies
- Dwingeloo Obscured Galaxy Survey (DOGS): radio survey of ZOA for 21cm lines indicating galaxies
- Effective Radius (Re): radius of a galaxy within which 1/2 the light is emitted
- Escape Fraction: fraction of ionizing photons escaping a body
- Extended Chandra Deep Field-South Survey (ECDFS): 1100 square arcminute x-ray survey
- Extended Groth Strip (EGS): region of sky searched for distant galaxies
- Faber-Jackson Relation: relation between elliptical galaxy luminosity and stellar velocity dispersion
- Faint Infrared Grism Survey (FIGS): survey to identify redshift of distant galaxies
- Fairall Galaxy List (Frl,Fairall): 1977 list of galaxies with bright nuclei
- Fanaroff-Riley Classification: a classification of the radio characteristics of radio sources
- FIRE Simulations: high resolution simulation of galaxies
- Freeman's Law: all spiral galaxy's have the same central surface brightness
- Fundamental Plane: three-way relation between elliptical galaxy characteristics
- Galactic Electron Density: density of electrons in the ISM
- Galactic Halo: spherical region around a galaxy with gas, dark matter, etc.
- Galaxy Bias: degree to which galaxy density fails to correspond to dark matter density
- Galaxy Classification: morphological classification of galaxies
- Galaxy Cluster (CL): large group of galaxies gravitationally-bound to the group
- Galaxy Filament: thread-like formations of galaxies, 50 to 80 megaparsecs
- Galaxy Formation: modeled as collapsing clouds
- Galaxy Group: group of fifty or fewer gravitationally bound milky-way-sized galaxies
- Galaxy Main Sequence: relation between galaxies' star formation and stellar mass
- Galaxy Merger: combination of galaxies upon collision
- Galaxy Power Spectrum: a power spectrum describing the occurrence of galaxies in space
- Galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- GALEX Arecibo SDSS Survey (GASS): HI survey of many galaxies
- GAMA: galaxy spectroscopy survey to roughly 1 Mpc
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- Globular Cluster Luminosity Function (GCLF): distribution of brightness of globular clusters
- GOODS NICMOS Survey (GNS): survey with HST NICMOS instrument of galaxies in GOODS fields
- Great Debate: historical debate regarding the nature of galaxies
- Halo Abundance Matching (HAM): method of comparing observed galaxies with cosmology models
- Hawaii K-Band Galaxy Survey: near-infrared survey of a selection of fields
- Herschel Redshift Survey (HeRS): 70 square-degree survey of galaxies redshifted 1.8 to 3.5
- Hierarchical Assembly of Galaxies: development of large galaxies by combining small ones
- Holmberg Radius: a measure of size of galaxy based on surface brightness
- Hubble Deep Field (HDF): highly-detailed image of a small region of the sky taken with HST
- Hubble Deep Field South (HDF-S): small region of the southern sky explored with HST
- Hubble Diagram: diagram comparing redshift with distance
- Hubble Ultra-Deep Field (HUDF): extremely detailed HST image of a small region of space
- Intergalactic Medium (IGM): matter between galaxies
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
- Kiso Survey of Ultraviolet Excess Galaxies (KUG): 1980 Japanese survey
- KMOS3D: survey of galaxies before to after peak star formation
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- Luminosity Function (LF): function giving number of stars or galaxies at different luminosities
- Mass Transport: transfer of mass from one part of a body/disk to another
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- MOJAVE: program to monitor AGN jet radio brightness and polarization
- Molecular Cloud Turbulence: observed turbulence in molecular clouds
- Morgan Classification: classification of galaxies by stellar spectrum and morphology
- Morphological Catalogue Of Galaxies (MCG): 1960s catalog from Palomar plates
- NASA/IPAC Extragalactic Database (NED): a database of galaxies and other objects outside the Milky Way
- New General Catalogue (NGC): 1888 catalog of galaxies, star clusters, and other nebulae
- NOAO Deep Wide-Field Survey (NDWFS): survey investigating large scale structure of the universe
- OB Association: stellar association with O or B class stars
- Open Cluster: group of stars within a galaxy apparently formed by a single cloud
- Palomar Four-Filter Survey (PC): Hale telescope survey aimed at discovering high-redshift quasars
- Parkes HI Zone Of Avoidance Survey (HIZOA): radio survey to identify galaxies hidden by the Zone of Avoidance
- PCA Analysis: an automatable method of determining galaxy morphology
- Peak Star-Formation Epoch: around 10 billion years ago when star formation peaked
- Planetary Nebula Luminosity Function (PNLF): model used in distance estimation
- Polar-Ring Catalog (PRC): 1990 catalog of polar-ring galaxies
- Principal Galaxies Catalog (PGC): modern catalog of more than 70k galaxies
- Protogalaxy: gas cloud forming a galaxy
- Quasar (QSO): distant, bright object that appears something like a star
- Radio Galaxy Zoo (RGZ): crowd-sourced classification of radio galaxies
- RASS/Green Bank Catalog (RGB,RASSGB): combined list of radio galaxies from Rosat and Green Bank surveys
- Roma-BZCAT: 2013 catalog of blazars
- Rotation Curve: function of orbital speed to orbital radius for a galaxy
- Sérsic Profile: model of the relative surface brightness across a galaxy
- Scott Effect: bias toward finding clusters that have bright galaxies
- SINS: near-infrared study of distant luminous galaxies
- Spitzer Extended Deep Survey (SEDS): survey of galaxy mass and black holes through life of the universe
- Spitzer HETDEX Exploratory Large Area Survey (SHELA): Spitzer-based survey of galaxies
- Star Formation Feedback: mechanisms whereby star formation regulates its own rate
- Star Formation History (SFH): star formation rate as a function of time
- Star Formation Rate (SFR): rate at which material such as gas is turned into stars
- Star-Formation Rate Stellar-Mass Ratio: ratio between a galaxy's stellar mass and its SF rate
- Stellar Association: like a large open cluster but even less tightly bound
- Stellar Nucleus: group of many stars at the center of a galaxy
- Stellar Population Synthesis (SPS): using spectral characteristics of galaxies to characterize their stellar populations
- Subaru Deep Field (SDF): survey of a small region of the sky using the Subaru telescope
- Subaru XMM-Newton Deep Survey (SXDS): survey using the Subaru telescope and XMM-Newton
- Submillimeter Galaxy Designator: designation system of submillimeter galaxies
- Supermassive Black Hole (SMBH): black hole with a mass of millions to billions of solar masses
- Tidal Arm: arm of gas and potentially stars leading from a galaxy
- TiNy Titans (TNT): study of dwarf galaxy pairs
- Tully-Fisher Relation (TFR): relation between spiral galaxy luminosity and line width
- Two Micron All-Sky Survey (2MASS): near-infrared survey of both hemispheres
- Uppsala General Catalogue (UGC): 1979 catalog of galaxies visible from northern hemisphere
- WiggleZ: a survey aiming at mapping dark energy
- WINGS: all-sky survey investigating known galaxy clusters
- WISeREP: interactive catalog of supernovae
- Galaxies With High Surface Brightness:
- Galaxy: gravitationally-bound group of stars
- Galaxy And Mass Assembly Survey:
- GAMA: galaxy spectroscopy survey to roughly 1 Mpc
- Galaxy Bias: degree to which galaxy density fails to correspond to dark matter density
- Galaxy Bimodality:
- Galaxy: gravitationally-bound group of stars
- Galaxy Classification: morphological classification of galaxies
- Galaxy Cluster (CL): large group of galaxies gravitationally-bound to the group
- galaxy clusters:
- Galaxy Color Magnitude Diagram:
- Galaxy Diagram:
- Galaxy Evolution Explorer (GALEX): observatory-satellite with 50cm ultraviolet telescope
- Galaxy Feedback:
- Galaxy Filament: thread-like formations of galaxies, 50 to 80 megaparsecs
- Galaxy Formation: modeled as collapsing clouds
- Galaxy Group: group of fifty or fewer gravitationally bound milky-way-sized galaxies
- Galaxy Interaction:
- Galaxy Merger: combination of galaxies upon collision
- Tidal Tail: string of mass ejected by a tidal forces in a neutron star merger
- Galaxy Luminosity Function:
- Luminosity Function (LF): function giving number of stars or galaxies at different luminosities
- Galaxy Main Sequence: relation between galaxies' star formation and stellar mass
- Galaxy Merger: combination of galaxies upon collision
- Galaxy Merger Mass Ratio:
- Galaxy Merger Timescale:
- galaxy nucleus:
- Active Galactic Nucleus (AGN): central region of a galaxy with extremely high luminosity
- Galactic Center: region at the middle of the Milky Way
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- Galaxy Power Spectrum: a power spectrum describing the occurrence of galaxies in space
- Galaxy Rotation Curve:
- Rotation Curve: function of orbital speed to orbital radius for a galaxy
- Galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- Galaxy Sheet:
- Galaxy Spectral Energy Distribution:
- Galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- galaxy supercluster:
- galaxy type:
- Galaxy Wall:
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- Galaxy Zoo: Hubble:
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galerkin Method:
- GALEX:
- GALEX Arecibo SDSS Survey (GASS): HI survey of many galaxies
- GALFA-HI:
- Galilean Frame Of Reference:
- Galilean Moons:
- Jupiter: largest planet in the solar system
- Moon: Earth's natural satellite
- Galilean Relativity:
- Relativity: physics models accommodating the constancy of the speed of light
- Galilean Transform:
- Relativity: physics models accommodating the constancy of the speed of light
- GALILEO:
- Galileo Observatory: infrared observatory-plane in the early 1970s
- GalMC:
- GAMA: galaxy spectroscopy survey to roughly 1 Mpc
- Gamma Leporis A:
- F-Type Star (F): type of star with about 1.5 times the mass of the Sun
- Gamma Rays: electromagnetic radiation, wavelength 10 picometers and less
- Gamma-Ray Burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Gamma-ray Large Area Space Telescope:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Gamow Factor:
- Gamow Peak: relative speed most likely to cause atoms to fuse
- Gamow Peak: relative speed most likely to cause atoms to fuse
- Ganymede: well-known Jupiter moon
- gas:
- Gas Blowout:
- Gas Constant:
- Gas Disk Migration:
- Gas Dwarf:
- Super-Earth: exoplanet more massive than Earth but substantially less than Neptune
- Gas Excitation:
- Gas Extinction:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Gas Flow: dynamics of gas, plasma, i.e. compressible fluids
- Gas Fraction: fraction of a galaxy or cluster consisting of gas
- Gas Fraction Estimation: methods of estimating various amounts of gas in galaxies
- Gas Giant: large planet made largely of gas
- Acetylene (C2H2): compound of two carbon and two hydrogen atoms
- Gas Mass Fraction:
- Gas Fraction: fraction of a galaxy or cluster consisting of gas
- Gas Planet: planet made largely of gas
- Gas Streamer: stream of gas
- Gas Torus:
- Io: well-known Jupiter moon
- Gaseous Envelope:
- Gasoline:
- GASS:
- Gaunt Factor:
- Gauss (G,Gs): measurement of magnetic field β
- Gauss's Law:
- Gaussian Distribution:
- Gaussian Function: function producing the bell curve
- GB300:
- GB6:
- GBM:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- GBT:
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- Green Bank Telescope (GBT): West Virginia large radio telescope
- GC:
- GCLF:
- GCM:
- GCVS:
- Gemini North:
- Gemini Observatory: pair of telescopes in Hawaii and Chile
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- Gemini South:
- General Catalogue of Nebulae and Clusters of Stars:
- General Catalogue of Variable Stars (GCVS): 20th/21st century catalog of 58000 variable stars
- General Circulation Model (GCM): climate model of a planet's atmosphere or ocean
- General Relativity (GR): formula relating gravity, space, time, and mass
- Geocentric System:
- Geochemistry: the chemistry of the Earth, planets, and moons
- Geodesic: equivalent to a straight line in curved space
- Geodynamo:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- geology:
- Geomagnetic Storm: disturbance in Earth's magnetosphere
- Geometrical Theory of Diffraction:
- geometry:
- Geopotential Model:
- J2: geopotential coefficient regarding a planet's oblateness
- Geosignature: geological sign of consequences of life
- geostationary:
- Orbital Speed: speed of an orbiting body around the barycenter of a system
- Geostrophic Balance:
- Thermal Wind: wind from pressure and the Coriolis force varying with altitude
- Geostrophic Wind:
- Thermal Wind: wind from pressure and the Coriolis force varying with altitude
- German:
- ROSAT: 1990s German space x-ray telescope
- Germanium:
- R-Process: synthesization of elements through neutron capture faster than beta decay
- Germany:
- GES:
- Gaia: survey satellite at 400-1000 nanometers
- GG Tau: much-studied quadruple star system
- GG Tauri:
- GG Tau: much-studied quadruple star system
- GHRS:
- GI2T: optical interferometer in France
- GIADA:
- Rosetta: space probe that visited a comet
- GIANO:
- Giant Impact:
- Impact: collision of one solid body with another
- Giant Impact Hypothesis:
- Moon: Earth's natural satellite
- Giant Impact Theory:
- Impact: collision of one solid body with another
- Giant Impacts:
- Giant Magellan Telescope (GMT): 24.5 meter telescope under construction
- Giant Metrewave Radio Telescope (GMRT): large radio interferometer in India
- Giant Molecular Cloud (GMC): interstellar gas cloud with molecules, thousands of solar masses
- Giant Planet: planet of more than 10 Earth masses
- giant planets:
- Helium Rain: possible source of heat in giant planet atmospheres
- Giant Radio Galaxy:
- Giant Radio Source:
- Radio Source (RS): something in the sky generating radio signal
- Giant Segmented Mirror Telescope (GSMT): concept for an extremely large telescope
- Giant Star: star larger than main sequence stars
- GIMIC:
- EAGLE: simulation of galaxy formation and evolution
- Gini:
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- Gini-M20:
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- GISMO: 2 mm bolometer camera on IRAM 30m telescope
- GIZMO:
- GJ:
- GJ 1132:
- GJ 1132 b: Earth-like extrasolar planet discovered in 2015
- GJ 1132 b: Earth-like extrasolar planet discovered in 2015
- GJ 1214:
- GJ 1214 b: super-Earth extrasolar planet discovered in 2009
- GJ 1214 b: super-Earth extrasolar planet discovered in 2009
- GJ 3053:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- GK Dwarf:
- GLAS:
- GLAST:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Gliese 1132:
- GJ 1132 b: Earth-like extrasolar planet discovered in 2015
- Gliese 1132 b:
- GJ 1132 b: Earth-like extrasolar planet discovered in 2015
- Gliese 1214:
- GJ 1214 b: super-Earth extrasolar planet discovered in 2009
- Gliese 1214 b:
- GJ 1214 b: super-Earth extrasolar planet discovered in 2009
- Gliese 191:
- Gliese 388:
- Gliese 411:
- Gliese 436 b:
- Gliese 581:
- M-Type Star (M): type of star with a temperature in the vicinity of 2500K
- Gliese 65:
- Gliese-Jahreiss Catalog (GJ): 1991 catalog of stars within 25 parsecs
- GLIMPSE:
- Global Climate Model:
- Global Microlensing Alert Network:
- GMAN: automated survey to identify microlensing transients
- Globular Cluster (GC): spherical group of stars orbiting a galaxy
- Globular Cluster Luminosity Function (GCLF): distribution of brightness of globular clusters
- Luminosity Function (LF): function giving number of stars or galaxies at different luminosities
- globular clusters:
- Glue: visualization software good for astrophysical data
- Gluon:
- Gly:
- Glycine (Gly,G): smallest of the twenty common amino acids
- Glycine (Gly,G): smallest of the twenty common amino acids
- GMACS:
- GMAN: automated survey to identify microlensing transients
- GMC:
- GMOS:
- GMRT:
- GMT:
- GMT - CfA Large Earth Finder:
- G-CLEF: spectrograph on the GMT
- GMT-Consortium Large Earth Finder:
- G-CLEF: spectrograph on the GMT
- GMTIFS:
- GMTNIRS:
- GN:
- GNS:
- GOBELINS:
- Goddard High Resolution Spectrograph:
- HRS: high resolution spectrography
- Goddard IRAM Superconducting Two Millimeter Camera:
- GISMO: 2 mm bolometer camera on IRAM 30m telescope
- Goddard Space Flight Center (GSFC): NASA space research laboratory near Washington D.C.
- Goldilocks Zone:
- GOLF:
- GOODS: survey combining data from different sources on very distant objects
- GOODS NICMOS Survey (GNS): survey with HST NICMOS instrument of galaxies in GOODS fields
- GOODS-N:
- GOODS: survey combining data from different sources on very distant objects
- GOODS-North:
- GOODS: survey combining data from different sources on very distant objects
- GOODS-S:
- GOODS: survey combining data from different sources on very distant objects
- GOODS-South:
- GOODS: survey combining data from different sources on very distant objects
- Gould Belt:
- Gould's Belt: ring of stars around the sky
- Gould's Belt Distances Survey (GOBELINS): survey of parallax distances to Gould's Belt YSOs
- GPC:
- GPI:
- GPIPS:
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- GPR:
- Radar: probe based on reflecting radio waves
- GPS:
- GR:
- GR1D: core collapse supernova simulation in 1D with GR
- Grams Per Mole:
- Gran Telescopio Canarias (GTC): 10.4 meter telescope in the Canary Islands
- Gran Telescopio Milimétrico:
- Grand Design Spiral Galaxy: spiral galaxy with two just two arms that are well-defined
- Grand Interféromètre a 2 Télescopes:
- GI2T: optical interferometer in France
- Grand Unified Theory:
- Electroweak: single conception including both electromagnetic and weak forces
- Granulation:
- Sun: star at center of solar system
- graph:
- Error Bar: feature of a graph to indicate accuracy
- Graph Theory:
- Dendrogram: diagram of a "tree", i.e., of a graph without cycles
- Grating: spectrometer component
- Grating Prism:
- Grism: combination of a grating and a prism
- Grating Spectrometer:
- Gravitational Collapse: shrinking of an object from gravitational force
- Gravitational Collapse Energy:
- Gravitational Constant: indicates how much pull between two masses
- Gravitational Harmonics:
- J2: geopotential coefficient regarding a planet's oblateness
- Gravitational Instability:
- Gravitational Instability Model: model for the formation of giant planets
- Gravitational Lens:
- Gravitational Lensing: focusing electromagnetic radiation by gravitational force
- Gravitational Locking:
- Gravitational Microlensing: gravitational lensing by "small" objects such as individual stars and planets
- Gravitational Moment:
- J2: geopotential coefficient regarding a planet's oblateness
- Gravitational Potential: conceptual field indicating the strength of gravity at each point
- Gravitational Potential Energy:
- Gravitational Pumping:
- Gravitational Quadrupole Radiation:
- Gravitational Radius:
- Gravitational Redshift: redshift due to GR effects of gravity
- Gravitational Scattering:
- Gravitational Separation:
- Gravitational Spectrum:
- J2: geopotential coefficient regarding a planet's oblateness
- Gravitational Time Dilation:
- Gravitational Wave (GW): ripples in the curvature of spacetime propagating as a wave
- Gravitational Wave Background:
- Gravitational Wave Detection:
- Gravitational Wave Detector:
- Gravitational Wave Event:
- Gravitational Wave Strain: a measure of the magnitude of a gravitational wave
- gravitational waves:
- Gravitational-Wave Memory: a gravitational wave that does not return
- Gravity: theory that mass attracts
- Gravity Harmonics:
- J2: geopotential coefficient regarding a planet's oblateness
- Gravity Sounding: measuring a planet's gravitation field by study of nearby probe flights
- Gravity Spectrum:
- J2: geopotential coefficient regarding a planet's oblateness
- Gravity Wave: wave in fluid where restoring force is gravity
- Gravity-sensitive Spectral Lines:
- Gray Atmosphere: a model atmosphere whose opacity does not depend upon wavelength
- GRB:
- Gamma-Ray Burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Great Andromeda Nebula:
- Andromeda (M31): spiral galaxy in the Local Group
- Nebula: cloud of dust and gas
- Great Attractor: gravity anomaly at the center of our supercluster
- Great Circle:
- Meridian: circle around the Earth passing through both poles
- Great Debate: historical debate regarding the nature of galaxies
- Great Observatories Origins Deep Survey:
- GOODS: survey combining data from different sources on very distant objects
- Great Void:
- Void: empty spaces between large scale structures
- Great Wall: large slab of galaxies
- green:
- G Band: band of visible light around 5100 angstroms
- Green Bank 140 Foot Telescope: West Virginia radio telescope
- Green Bank 300ft Telescope (GB300): former large radio telescope at Green Bank
- Green Bank 6-cm Radio Source Catalog (GB6): catalog of from 1980s northern-hemisphere radio survey
- Green Bank 90m Telescope:
- Green Bank 91m Telescope:
- Green Bank Observatory:
- Green Bank Telescope (GBT): West Virginia large radio telescope
- Green Bank Ultimate Pulsar Processing Instrument:
- GUPPI: radio-telescope instrument aimed at observing pulsars
- Green Valley:
- Green Valley Galaxy:
- Greenhouse Effect: mechanism that boosts temperature through selective blocking of EMR
- Greenhouse Gas:
- Earthshine: reflected and electromagnetic radiation from Earth
- Greenhouse Effect: mechanism that boosts temperature through selective blocking of EMR
- Radiative Forcing (RF): difference between a planet's incoming and outgoing radiation
- Greenwich Meridian:
- Meridian: circle around the Earth passing through both poles
- Greenwood Time Constant:
- Seeing: apparent blurring and twinkling of objects seen through atmosphere
- Gregorian Telescope: type of reflecting telescope
- Greisen-Zatsepin-Kuzmin Limit:
- GRG:
- Galaxy Group: group of fifty or fewer gravitationally bound milky-way-sized galaxies
- Radio Galaxy (RG): a galaxy emitting a lot of radio
- GRID:
- AGILE: Italian space gamma-ray observatory
- Grism: combination of a grating and a prism
- Gross Structure:
- Fine Structure: spectral lines due to electron spin and relativistic effects
- Hyperfine Structure: spectral lines due to magnetic and spin interactions between electrons nucleus
- Groth Strip:
- Groth Survey Strip:
- ground:
- Ground State:
- Ground-penetrating Radar:
- Radar: probe based on reflecting radio waves
- Group of Galaxies:
- Galaxy Group: group of fifty or fewer gravitationally bound milky-way-sized galaxies
- GRS:
- Radio Source (RS): something in the sky generating radio signal
- Grus Wall:
- GS:
- Gauss (G,Gs): measurement of magnetic field β
- GOODS: survey combining data from different sources on very distant objects
- Juno: mission to Jupiter
- GSAOI:
- GSC:
- GSC-I:
- GSC-II:
- GSFC:
- GSFC xray.page and EUV Spectroheliograph:
- OSO 7: 1970s observatory-satellite for viewing the Sun
- GSMT:
- GSS:
- GTC:
- GTCAO-FRIDA:
- Guide Star:
- Guide Star Catalog (GSC,HSTGC): catalog of stars to help aim HST
- Guillotine Factor:
- Gunn-Peterson Trough: spectral feature in EMR from redshift 6+
- Guo Shoujing Telescope:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- GUPPI: radio-telescope instrument aimed at observing pulsars
- GUT:
- Electroweak: single conception including both electromagnetic and weak forces
- GW:
- GW Memory:
- GW Strain:
- GW150914:
- Chirp: burst of signal rising or falling in frequency
- Gravitational Wave (GW): ripples in the curvature of spacetime propagating as a wave
- LIGO: pair of observatories to detect gravitational waves
- Gyrochronology: means of estimating stellar age from rotation
- GZ2:
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- GZK Limit: limit on energy of cosmic rays
- H:
- H and K Spectrometer:
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- H Band:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- H line:
- Calcium (Ca): element, Ca, atomic number 20
- Hα:
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- H-α:
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- H-Alpha Filter:
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- H-alpha Star Formation Rate:
- H-alpha to UV Ratio:
- H-OH:
- H-R Diagram (HRD): diagram relating effective temperature to luminosity
- H2:
- Hydrogen (H): most prominent element, atomic number 1
- H2/CO Conversion Ratio:
- H0:
- H2:
- Hydrogen (H): most prominent element, atomic number 1
- H2 Dissociation Front:
- H++:
- H+:
- Ha:
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- HabEx: proposed space mission to directly image exoplanets
- Habitability: ability of a planet to support life
- Habitability Zone:
- Habitable Exoplanet Imaging Mission:
- HabEx: proposed space mission to directly image exoplanets
- Habitable Zone (HZ): zone where conditions are favorable for life
- Hadar:
- Hadley Cell: circulation pattern of up at the equator, out, down, and back
- Hadley Circulation:
- Hadley Cell: circulation pattern of up at the equator, out, down, and back
- Hadron:
- Baryon: protons, neutrons, and other three-quark particles
- Particle: very small thing
- Pion (π): first type of meson discovered
- HALCA:
- Hale Telescope: 5.1m reflector telescope in California
- Haleakala:
- Haleakala Observatory:
- Half Life:
- Hall Effect: voltage generated by interacting current and magnetic field
- Magnetometer: instrument to measure the strength of a magnetic field
- Halo:
- Halo Abundance Matching (HAM): method of comparing observed galaxies with cosmology models
- Halo Mass Function: mass of distribution of dark matter
- Halo Model:
- Halo Star:
- HAM:
- Hamburg/ESO Survey (HE): 1990s southern hemisphere survey aimed at finding quasars
- Hamiltonian: mathematical transform useful in mechanics
- Hamiltonian Function:
- Hamiltonian: mathematical transform useful in mechanics
- Hamiltonian Mechanics:
- Hamiltonian: mathematical transform useful in mechanics
- Hard X-Ray:
- X-ray: electromagnetic radiation, wavelength .01 to 10 nanometers
- Hardening Rate:
- Hardness: measure of the binding energy of a binary
- Hardness: measure of the binding energy of a binary
- Harlan J. Smith Telescope:
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- HARMONI:
- harmonics:
- HARP:
- HARPS: high-precision spectrograph for exoplanet searches
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- Hartley 2Extrasolar Planet Observation and Characterization:
- EPOXI: mission using Deep Impact for further exploration
- Harvard College Observatory:
- DASCH: project to digitize old astronomy plates
- Harvard Revised Photometry Catalog:
- HAT:
- Hat Creek Radio Observatory:
- HAT-1:
- HATNet: distributed array of telescopes to search for transients
- HAT-South:
- HATNet: distributed array of telescopes to search for transients
- HATNet: distributed array of telescopes to search for transients
- HATS:
- HATNet: distributed array of telescopes to search for transients
- Haumea:
- Hawaii:
- Hawaii Deep Survey:
- Hawaii K-Band Galaxy Survey: near-infrared survey of a selection of fields
- Hawaii Survey:
- HAWC:
- HAWK-I:
- Hawking Radiation:
- Black Hole (BH): region of such high mass that light cannot escape
- Hayashi Track: H-R diagram track of evolution of some pre-main-sequence stars
- HB:
- Horizontal Branch (HB): a second "giant" stage in the evolution of some main sequence stars
- HB87:
- HB89:
- HB93:
- HBK: study of M31 globular clusters
- HC:
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- HCI: imaging of targets very near bright objects
- HCN:
- HCO+:
- HCS:
- HCI: imaging of targets very near bright objects
- Subaru Telescope: 8.2 meter telescope in Hawaii
- HD:
- HD 209458 b: hot jupiter discovered in 1999
- HD 80606 b: hot jupiter discovered in 2001
- HD 95735:
- HDE:
- HDF:
- Hubble Deep Field (HDF): highly-detailed image of a small region of the sky taken with HST
- HDF-S:
- HDS:
- HDST:
- He:
- Hamburg/ESO Survey (HE): 1990s southern hemisphere survey aimed at finding quasars
- Helium (He): non-metallic element, He, atomic number 2
- Headlight Effect:
- HEAO A-1 X-ray Source Catalog:
- HEAO-1: 1977 x-ray observatory space mission
- HEAO B:
- HEAO-2: 1978 x-ray observatory space mission
- HEAO-1: 1977 x-ray observatory space mission
- HEAO-2: 1978 x-ray observatory space mission
- HEASARC: archive of NASA data on high energy astronomy
- Hectochelle:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Hectospec:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Heinrich Hertz Submillimeter Telescope:
- Heisenberg Uncertainty Principle:
- Heisenburg Uncertainty Principle:
- Heliocentric Julian Day:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Heliocentric System: model of the universe with the planets orbiting the Sun
- Heliocentricity:
- Epicycle: small circular motion around a large circular motion
- Heliocentric System: model of the universe with the planets orbiting the Sun
- Heliocentrism:
- Heliopause: boundary between solar wind and the interstellar medium
- helioseismology:
- Heliosheath: region just beyond the heliosphere
- Heliosphere: region of space dominated by the Sun
- Heliosheath: region just beyond the heliosphere
- Voyager: space probes to observe planets and the edge of the solar system
- Heliospheric Current Sheet:
- Current Sheet: narrow sheet within a magnetic field where current flows
- Helium (He): non-metallic element, He, atomic number 2
- Helium Rain: possible source of heat in giant planet atmospheres
- Helium Abundance:
- Helium (He): non-metallic element, He, atomic number 2
- Helium Burning:
- Helium Core Flash:
- Helium Flash: helium ignition in a star
- Helium Rain: possible source of heat in giant planet atmospheres
- Helium Runaway Shell: helium ignition in a shell in AGB giants
- Helium Shell Flash:
- Helium White Dwarf:
- White Dwarf: stellar remnant of mostly electron-degenerate matter
- Henry Draper Catalog (HD): early 20th century spectroscopic catalog of stars
- Henry Draper Extension:
- Her-CrB GW:
- HERA: low frequency radio telescope
- Herbig Ae/Be Star:
- Herbig-Haro Object (HH): illuminated nebula from colliding jets
- Hercules Cluster:
- Galaxy Cluster (CL): large group of galaxies gravitationally-bound to the group
- Hercules Supercluster:
- Hercules-Corona Borealis Great Wall (Her-CrB GW): large slab of galaxies discovered in 2013
- HERITAGE:
- SAGE: survey of gas and dust in the Magellanic Clouds
- HERMES: four-channel spectrograph on the Anglo-Australian Telescope
- HeRS:
- Herschel:
- Herschel Inventory of the Agents of Galaxy Evolution:
- SAGE: survey of gas and dust in the Magellanic Clouds
- Herschel Orion Protostar Survey (HOPS): survey of SEDs of YSOs in Orion
- Herschel Redshift Survey (HeRS): 70 square-degree survey of galaxies redshifted 1.8 to 3.5
- Herschel Space Observatory: infrared observatory-satellite with 3.5 meter reflector
- Herschel Telescope:
- Herschelian Telescope: type of off-axis reflecting telescope
- Hertz:
- Jansky (Jy): unit of measurement of spectral flux density
- Hertzsprung Gap:
- H-R Diagram (HRD): diagram relating effective temperature to luminosity
- Hertzsprung-Russell diagram:
- H-R Diagram (HRD): diagram relating effective temperature to luminosity
- HESS:
- HET:
- HETDEX:
- Heterosphere:
- Homopause: level of atmosphere up to which components are mixed
- HETGS:
- Heuristic Habitable Zone:
- Hewitt & Burbidge Catalog (HB87): optical catalog of quasi-stellar objects
- HEXTE:
- RXTE: space mission to time X-ray variations
- HFI:
- Planck: microwave telescope in space
- HFLS3: very distant starburst galaxy
- HH:
- HH Andromedae:
- HHSMT:
- HI:
- HI Cloud:
- HI Region (HI): cloud of neutral atomic hydrogen
- HI Line:
- 21cm Line: hydrogen line useful for determining redshift
- HI Parkes All Sky Survey:
- HI Region (HI): cloud of neutral atomic hydrogen
- HI Supershell: bubbles of HI hundreds of light-years across
- HiCIAO:
- Hierarchical Assembly of Galaxies: development of large galaxies by combining small ones
- HIFI:
- Higgs Boson:
- High Accuracy Radial Velocity Planet Searcher:
- HARPS: high-precision spectrograph for exoplanet searches
- High Accuracy Radial Velocity Planet Searcher for the Northern Hemisphere:
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- High Contrast Imaging:
- HCI: imaging of targets very near bright objects
- High Contrast Spectrography:
- HCI: imaging of targets very near bright objects
- High Contrast Spectroscopy:
- HCI: imaging of targets very near bright objects
- High Definition Space Telescope (HDST): proposed 12m space telescope
- High Energy Astronomy Observatory 1:
- HEAO-1: 1977 x-ray observatory space mission
- High Energy Astrophysics Observatory 2:
- HEAO-2: 1978 x-ray observatory space mission
- High Energy Astrophysics Science Archive Research Center:
- HEASARC: archive of NASA data on high energy astronomy
- High Energy Stereoscopic System (HESS): ground gamma-ray telescope array
- High Resolution Shock Capture (HRSC): method of modeling shock waves
- High Resolution Spectrograph:
- HRS: high resolution spectrography
- High Resolution Spectrography:
- HRS: high resolution spectrography
- High Throughput X-ray Spectroscopy Mission:
- XMM-Newton: x-ray observatory-satellite operated by ESA
- High-Altitude Water Cherenkov Experiment:
- High-Altitude Water Cherenkov Observatory (HAWC): gamma ray telescope using Cherenkov radiation
- High-Resolution J:
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- High-Surface-Brightness Galaxy:
- High-Velocity Cloud (HVC): clouds in galactic halos
- High-Velocity Star: star moving noticeably faster than neighbors
- Higher-Order Method:
- Higher-Order Multiple Star System:
- HII:
- HII Cloud:
- HII Region (HII): cloud of partially-ionized atomic hydrogen
- HII Region (HII): cloud of partially-ionized atomic hydrogen
- HII Region Size--Galactic Luminosity Relation:
- HII Region (HII): cloud of partially-ionized atomic hydrogen
- HiJak:
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- Hill Radius: radius of gravitational influence of a body
- Hill Sphere:
- Hill Radius: radius of gravitational influence of a body
- Hill Stability: planetary orbits which will remain in the same order
- HIP:
- Hipparcos: ESA astrometry space observatory circa 1990
- HIP 45982 b:
- HIPASS: HI survey
- Hipparchus: Greek astronomer who developed concept of magnitude
- Hipparcos: ESA astrometry space observatory circa 1990
- Hipparcos Catalog:
- Hipparcos: ESA astrometry space observatory circa 1990
- HIRES:
- HiRISE:
- HITEMP: spectroscopic parameters for modeling gas optics
- Hitomi:
- ASTRO-H: Japanese space x-ray telescope
- HITRAN: spectroscopic parameters for modeling atmospheric optics
- HIZOA:
- HIZSS:
- HJ:
- Hot Jupiter (HJ): Jupiter-sized gas exoplanet orbiting very close to star
- HJD:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- HL Tau: much-studied T-Tauri star
- HL Tauri:
- HL Tau: much-studied T-Tauri star
- HLIRG:
- HMI:
- HNC:
- Hobbit Galaxy:
- Hobby-Eberly Telescope (HET): 9.2 meter telescope in Texas
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- Hobby-Everly Telescope Dark Energy Experiment:
- Holmberg Radius: a measure of size of galaxy based on surface brightness
- Homochirality:
- Homologous Collapse: collapse of a uniform sphere of material
- Homopause: level of atmosphere up to which components are mixed
- Homosphere:
- Homopause: level of atmosphere up to which components are mixed
- Hooker Telescope:
- Hopkins Ultraviolet Telescope (HUT): 1990s ultraviolet space telescope used on two shuttle missions
- HOPS:
- horizon:
- Horizon Distance:
- Horizon Problem:
- Inflation: theorized rapid expansion of the very early universe
- Horizontal Branch (HB): a second "giant" stage in the evolution of some main sequence stars
- Horizontal Coordinate System: celestial coordinate system based upon horizon and north
- Horn Feed:
- Phased Array: method of using a set of antennas directionally
- HORS:
- Hot Dark Matter:
- Cold Dark Matter (CDM): one of three "dark matter" theories
- Dark Matter: matter hypothesized to provide galaxies with mass that can't be viewed
- Hot DOG: high-energy galaxy with a lot of dust
- Hot Dust-Obscured Galaxy:
- Hot DOG: high-energy galaxy with a lot of dust
- Hot Dust-Obscured Object:
- Hot DOG: high-energy galaxy with a lot of dust
- Hot Jupiter (HJ): Jupiter-sized gas exoplanet orbiting very close to star
- Hot Mass Accretion:
- Hot Neptunes:
- Hot Start:
- Hour:
- Hour Angle:
- Hour Circle:
- HPF:
- HR:
- HR 8799: star with four exoplanets
- HRC:
- HRD:
- H-R Diagram (HRD): diagram relating effective temperature to luminosity
- HRI:
- HEAO-2: 1978 x-ray observatory space mission
- ROSAT: 1990s German space x-ray telescope
- HRS: high resolution spectrography
- HRS-2:
- HRSC:
- HSB Galaxy:
- HSP:
- HST:
- HST-1:
- M87: supergiant elliptical galaxy
- HSTGC:
- HTT:
- Huan Tran Telescope:
- Hubble Constant (H0): rate of expansion of the universe
- Hubble Deep Field (HDF): highly-detailed image of a small region of the sky taken with HST
- Hubble Deep Field South (HDF-S): small region of the southern sky explored with HST
- Hubble Diagram: diagram comparing redshift with distance
- Hubble Expansion:
- Hubble Extreme Deep Field:
- Hubble Deep Field (HDF): highly-detailed image of a small region of the sky taken with HST
- Hubble Flow:
- Hubble Law:
- Hubble Parameter:
- Hubble Sequence:
- Hubble Space Telescope (HST): observatory-satellite with 2.4 meter reflective telescope
- Hubble Space Telescope Guide Catalog:
- Hubble Time:
- Hubble Type:
- Hubble Ultra-Deep Field (HUDF): extremely detailed HST image of a small region of space
- Hubble's Law:
- HUDF:
- HUDF09:
- Hulse-Taylor Binary (PSR B1913+16,PSR J1915+1606, PSR 1913+16): binary system consisting of a pulsar and neutron star
- Hulse-Taylor Pulsar:
- Hulse-Taylor Binary (PSR B1913+16,PSR J1915+1606, PSR 1913+16): binary system consisting of a pulsar and neutron star
- Humidity: amount of water vapor in a portion of the atmosphere
- Humphreys Series:
- Hydrogen (H): most prominent element, atomic number 1
- Hungarian:
- HATNet: distributed array of telescopes to search for transients
- Hungarian Automated Telescope Network:
- HATNet: distributed array of telescopes to search for transients
- HUT:
- Huygens:
- Cassini: explorer spaceship sent to Saturn
- Huygens-Fresnel Principle:
- HV:
- HVC:
- HVS:
- HVS2:
- HXD:
- HXI:
- ASTRO-H: Japanese space x-ray telescope
- HXT:
- ASTRO-H: Japanese space x-ray telescope
- Yohkoh: 1990s Japanese solar observatory spacecraft
- Hyades Cluster: nearest open cluster
- Hydra:
- Pluto: dwarf planet formerly listed as one of the nine planets
- Sloan Great Wall (SGW): large slab of galaxies discovered in SDSS
- Hydra and Centaurus Superclusters:
- Hydra-Centaurus Supercluster: near neighbor of Local Supercluster
- Hydridocarbon:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Hydrocarbon (HC): any compound of just carbon and hydrogen
- Hydrodynamic Equations: equations describing the dynamics of fluids
- Hydrodynamic Escape: ongoing escape of gas particles from atmosphere
- Hydrodynamic Gas Loss:
- Hydrodynamic Model:
- Hydrodynamical Model:
- Hydrodynamics: study of liquids in motion
- Hydrogen (H): most prominent element, atomic number 1
- Hydrogen Bond:
- Ice: solid state of water
- Hydrogen Epoch of Reionization Array:
- HERA: low frequency radio telescope
- Hydrogen Intensity Mapping:
- Hydrogen Line:
- 21cm Line: hydrogen line useful for determining redshift
- Hydrogen Nitride:
- Ammonia (NH3): compound of nitrogen and hydrogen
- Hydrogen-Alpha Filter:
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- Hydrologic Cycle:
- Hydrology: study of the movement of water
- Hydrostatic Balance:
- Hydrostatic Equilibrium: state of a fluid body when forces are such that the fluid is at rest
- Hydroxide:
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- Hydroxyl Radical:
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- Hygiean:
- HyLIRG:
- Hyper Suprime-Cam:
- Hyperbola:
- Conic Section: orbit shapes, like the intersection of a plane and cone
- Keplerian Orbit: orbit following a perfect ellipse or other conic section
- Hyperfine Level:
- Hyperfine Structure: spectral lines due to magnetic and spin interactions between electrons nucleus
- Hyperfine Structure: spectral lines due to magnetic and spin interactions between electrons nucleus
- Fine Structure: spectral lines due to electron spin and relativistic effects
- Hypergiant: extremely bright stars
- Hypergiant Star:
- Hyperion: Monte-Carlo radiative transfer code
- Moon: Earth's natural satellite
- Saturn: second largest planet in the solar system
- Hyperluminous Infrared Galaxy (HLIRG, HyLIRG): a galaxy emitting a more far infrared than an ULIRG
- Hypernova:
- Hypervelocity Star (HVS,HV): star moving very much faster than usual
- HZ:
- HZE Ion:
- I:
- I Band: photometric filter for near infrared light
- i-Band:
- Iapetus:
- Moon: Earth's natural satellite
- Saturn: second largest planet in the solar system
- IAU:
- IAU Galactic Coordinate System:
- IBEX:
- IBEX-Hi:
- IBEX-Low:
- IBIS:
- INTEGRAL: European gamma ray observatory-satellite
- IC:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- IC 342: spiral galaxy in the Council of Giants
- IC 342/Maffei Group:
- IC 342: spiral galaxy in the Council of Giants
- ICAT:
- Ice: solid state of water
- Ice Giant: planet more massive than gas planets and less than rocky planets
- Snow Line: distance from protostar cool enough for water to condense
- Superionic Ice: odd state of water at high temperature and pressure
- Water-Ice Planet: planet made entirely of water ice
- Ice Dwarf:
- Ice Giant: planet more massive than gas planets and less than rocky planets
- Ice Line:
- Snow Line: distance from protostar cool enough for water to condense
- IceCube: neutrino detector at the South Pole
- IceCube Neutrino Observatory:
- IceCube: neutrino detector at the South Pole
- ICEMAG:
- ICM:
- Ideal Gas:
- Ideal Gas Law:
- IDL: interactive vector-oriented programming language
- IDST:
- IFS:
- IFTS:
- IFU:
- IFU Observation:
- IGM:
- IGR:
- INTEGRAL: European gamma ray observatory-satellite
- II:
- III:
- Illumination: measure of light energy producing a telescope's image
- Illustris Project: 2013-2015 series of cosmological simulations
- IllustrisTNG Project:
- IMACS:
- Image Scale:
- Plate Scale: relation between angle and distance across an image
- Image Slicer:
- Image Stabilization: camera mechanism to compensate for movement
- imager:
- imaging:
- Imaging Fourier Transform Spectroscope:
- Imaging Fourier Transform Spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
- Imaging Spectrograph:
- Imaging Spectrometer: device to capture spectrum point-by-point of an image
- Spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- IMAPS:
- IMBH:
- Black Hole (BH): region of such high mass that light cannot escape
- IMF:
- IMPACT:
- Impact: collision of one solid body with another
- STEREO: two-satellite system to observe the Sun
- Tillotson Equation: equation of state for high speed impacts
- Impact Erosion:
- Impact: collision of one solid body with another
- In Situ: on site
- In Situ Observation:
- INAF:
- Incidence:
- Inclination:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- Index Catalogue of Nebulae and Clusters of Stars:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
- India:
- Indian Initiative in Gravitational-wave Observations:
- LIGO-India: planned gravitational wave detector in India
- INDIGO:
- LIGO-India: planned gravitational wave detector in India
- Inertial Forces:
- Reynolds Number (Re): measure reflecting a fluid system's propensity to turbulence
- Inertial Frame Of Reference:
- Inertial Reference Frame: frame of reference where no force means no acceleration
- Inferior Planet:
- Infinitesimal Transform:
- Inflated Gas Giant:
- Hot Jupiter (HJ): Jupiter-sized gas exoplanet orbiting very close to star
- Inflated Radii: exceptionally large radii of some hot jupiters
- Inflation: theorized rapid expansion of the very early universe
- Inflation Theory:
- Inflation: theorized rapid expansion of the very early universe
- Inflationary Theory:
- Inflation: theorized rapid expansion of the very early universe
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- Infrared Astronomical Satellite:
- IRAS: 1983 satellite that surveyed the sky in infrared
- Infrared Astronomy:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- Infrared Dark Cloud (IRDC): molecular cloud not emitting nor transmitting infrared
- Infrared Optical Telescope Array:
- IOTA: optical interferometer
- Infrared Processing and Analysis Center:
- IPAC: Caltech group to collect and analyze infrared observations
- Infrared Science Archive:
- IRSA: archive center for infrared data from NASA missions
- Infrared Space Observatory (ISO): 60cm infrared space telescope
- Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
- Infrared Telescope Facility:
- IRTF: Mauna Kea 3-meter infrared telescope
- Infrared Window:
- Atmospheric Window: frequency bands in which the atmosphere passes electromagnetic radiation
- INGRID:
- Initial Fluctuation Spectrum: the power spectral density of the early universe
- Initial Mass Function (IMF): function describing initial mass of stars
- INMS:
- Cassini: explorer spaceship sent to Saturn
- Inner Lindblad Resonance:
- Inner Moon:
- Enceladus: Saturn moon considered possible carrier of life
- Inner Working Angle:
- Coronagraph: telescope feature to block light from a specific body
- Insolation: solar energy received in given time
- Instability Region: region around an object where orbits cannot persist
- Instability Strip: region of H-R diagram where stars are unstable
- Institut de radioastronomie millimétrique (IRAM): organized radio astronomy collaboration between France, Germany, and Spain
- Institut für Theoretische Astrophysik:
- Institute For Theoretical And Experimental Physics:
- Institute of Theoretical Astrophysics (ITA): Heidelberg research institute
- instrument:
- 4MOST: planned spectrograph for VISTA telescope
- CONCERTO: spectrometer aimed at mapping the [CII] line
- CorMASS: near-infrared spectrograph
- CRIRES: high resolution IR echelle spectrometer
- Dark Energy Spectroscopic Instrument (DESI): planned instrument for measuring red-shift of distant objects
- G-CLEF: spectrograph on the GMT
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- GISMO: 2 mm bolometer camera on IRAM 30m telescope
- GUPPI: radio-telescope instrument aimed at observing pulsars
- HARPS: high-precision spectrograph for exoplanet searches
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- HERMES: four-channel spectrograph on the Anglo-Australian Telescope
- Keck Planet Finder (KPF): spectrograph in development for Keck
- Keck Planet Imager And Characterizer (KPIC): proposed noise-reducing planet imager for Keck
- KMOS: 2-micron spectrograph on ESO VLT
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- MUSTANG: bolometer array on the Green Bank Telescope
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- POLARBEAR: instrument to map CMB polarization
- PUPPI: Arecibo radio-telescope instrument aimed at observing pulsars
- QUEST: sixteen square-degree survey camera
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- SpeX: a medium-resolution infrared spectrograph
- SPHERE: VLT instrument for imaging exoplanets
- TAIPAN: multi-object spectrograph with robot fiber-positioner
- Tomographic Ionized-Carbon Mapping Experiment (TIME): proposed instrument to map the [CII] line
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- WEAVE: spectrograph for the William Herschel Telescope
- Wide-Field Multi-Object Spectrograph (WFMOS): proposed instrument to detect baryon acoustic oscillations
- instrument type:
- instruments:
- INTEGRAL: European gamma ray observatory-satellite
- Integral Field Spectrograph: spectrograph that captures images
- Integral Field Spectrometer:
- Integral Field Spectroscopy:
- Integral Field Unit (IFU): instrument to allow a spectrograph to capture data over a 2d field
- Integrated Sachs-Wolfe Effect:
- Integration Time: time required to acquire signal
- Intensity: power reaching a surface from a specific source
- Intensity Mapping: measure of cosmic matter density
- Interactive Data Language:
- IDL: interactive vector-oriented programming language
- Interference: result of interaction of waves
- Interference Pattern:
- Interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- Interferometry: analysis of superimposed EMR waves
- Intergalactic Clouds:
- Lyman-Alpha Forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- Intergalactic Medium (IGM): matter between galaxies
- Intermediate Band Photometry:
- Photometry: studying starlight through bandpass filters
- Intermediate Polar:
- Intermediate-Mass Black Hole:
- Black Hole (BH): region of such high mass that light cannot escape
- Internal Gravity Wave: ripples in a change in density in a fluid
- Internal Wave:
- International Astronomical Union (IAU,UAI): association of professional astronomers
- International Gamma-Ray Astrophysics Laboratory:
- INTEGRAL: European gamma ray observatory-satellite
- International Pulsar Timing Array (IPTA): organization of pulsar timing arrays
- International Space Station:
- MAXI: Japanese X-ray camera on the International Space Station
- International System of Units:
- International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
- International Virtual Observatory Alliance:
- Interplanetary Medium (IPM): matter in the solar system around and between planets
- interpretation:
- CO to H2 Factor (Xco,XCO): assumed ratio between observed CO emission lines and H2 mass
- Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
- Interstellar Dust:
- Cosmic Dust: cosmic dust is dust in space such as interstellar dust
- Interstellar Extinction:
- Extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- Interstellar Holography: holographic analysis of incoming EMR to study the intervening ISM
- Interstellar Magnetic Field (ISMF): galactic magnetic field between that of stars
- Interstellar Medium (ISM): matter in a galaxy between star systems
- Interstellar Medium Absorption Profile Spectrograph (IMAPS): 1980s/1990s UV spectrometer
- Interstellar Reddening:
- Reddening: red appearance of astronomical objects because blue light is attenuated by dust
- Intertropical Convergence Zone (ITCZ): circulation pattern near equator where north and south Hadley cells meet
- Intracluster Gas:
- Intracluster Medium (ICM): hot plasma in center of a cluster
- Intrinsic Color Index:
- Color Index: a number that characterizes the color of an object
- Intrinsic S-Star:
- S-Type Star: type of star with lines indicating zirconium
- Inverse Beta Decay:
- Inverse Compton Scattering:
- Inverse Discrete Fourier Transform:
- Inverse Square Law: a value's dependency upon reciprocal of the square of the distance from something
- Inverse Volume Weighting:
- Io: well-known Jupiter moon
- Io Plasma Torus:
- Io: well-known Jupiter moon
- Io Torus:
- Io: well-known Jupiter moon
- Ion:
- Acidity (pH): measure of the activity of hydrogen ions in a solution
- C+: ionized carbon missing one electron
- Dark Age: interval when the universe's hydrogen atoms were neutral
- Epoch of Reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- Recombination: time when the universe's ionized hydrogen atoms neutralized
- Solar Energetic Particle (SEP): high-energy particles from the Sun
- State of Ionization: difference in an ion's electron count versus proton count
- Z+: symbol for ion or ion charge
- Ionic Bond:
- Ionic Ocean:
- Ionization:
- Ionization Front:
- Ionization State:
- Ionization Temperature:
- Ionized Interstellar Medium:
- IOTA: optical interferometer
- IPAC: Caltech group to collect and analyze infrared observations
- IPC:
- HEAO-2: 1978 x-ray observatory space mission
- IPM:
- IPTA:
- iPTF:
- IR:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- IR Star Formation Rate:
- IRAC:
- IRAM:
- IRAM 30m Millimeter Radio Telescope:
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS 16293-2422:
- IRAS F:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS Point Source Catalog:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS-FSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRAS-PSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRC:
- AKARI: Japanese space infrared telescope
- IRCAM:
- IRCS:
- IRDC:
- IREM:
- INTEGRAL: European gamma ray observatory-satellite
- Iridium:
- IRIS:
- Thirty Meter Telescope (TMT): extremely large telescope planned for Hawaii
- Voyager: space probes to observe planets and the edge of the solar system
- IRIS2:
- IRMS:
- Iron (Fe): metal, Fe, atomic number 26
- Iron Peak: relatively high abundance of iron and nearby elements
- Iron-56:
- Nickel (Ni): metal, Ni, atomic number 28
- Irradiance: power reaching a surface
- Irregular Galaxy:
- IRS:
- IRSA: archive center for infrared data from NASA missions
- IRSF:
- IRTF: Mauna Kea 3-meter infrared telescope
- IRTS:
- ISAAC:
- Isaac Newton Group of Telescopes:
- ISIS:
- ISM:
- ISMF:
- ISO:
- ISO Spectrum:
- ISOCAM:
- Isochrone:
- H-R Diagram (HRD): diagram relating effective temperature to luminosity
- ISOHDFS:
- Isolation Mass: mass of an oligarch after accreting all nearby planetesimals
- ISOPHOT:
- Isophote: line on a diagram indicating a level of brightness
- Isophoten:
- Isothermal Core: core region of a body of all the same temperature
- Isotope: subclass of an element with a specific number of nucleons
- Deuterium (D): hydrogen isotope with one neutron
- Isotope Fractionation:
- Isotope Notation:
- Isotope: subclass of an element with a specific number of nucleons
- Isotopic Fractionation:
- Isotropy: uniformity in all directions
- ISS:
- Voyager: space probes to observe planets and the edge of the solar system
- ISW:
- ITA:
- Italian:
- Italian National Institute of Astrophysics:
- Italian Space Agency:
- AGILE: Italian space gamma-ray observatory
- Italy:
- ITCZ:
- ITEP:
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
- Iterative Method:
- IUE:
- J:
- J Band:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- J Coefficients:
- J2: geopotential coefficient regarding a planet's oblateness
- J Designator: designator using ecliptic coordinates at year 2000
- J-MAG:
- JUICE: mission to Jupiter in development
- J-Type Shock:
- Shock Wave: abrupt propagating disturbance in a fluid
- J1407: star orbited by a companion with a ring system
- J2000 Epoch:
- Epoch: time on which to base celestial coordinates
- J2000 Equinox:
- Equinox: times when tilt of Earth is neither toward or away from the Sun
- J2000.0 Epoch:
- Epoch: time on which to base celestial coordinates
- J2000.0 Equinox: equinox as of the J2000.0 epoch used as a positional reference
- Equinox: times when tilt of Earth is neither toward or away from the Sun
- J20000 Epoch:
- Epoch: time on which to base celestial coordinates
- J2: geopotential coefficient regarding a planet's oblateness
- J3:
- J2: geopotential coefficient regarding a planet's oblateness
- Jacobi Constant:
- Jacobi Integral: method of solving some three-body problems
- JADE:
- James Clerk Maxwell Telescope (JCMT): far-infrared telescope in Hawaii
- James Webb Space Telescope (JWST): future space-based 6.5 meter infrared telescope
- Jansky (Jy): unit of measurement of spectral flux density
- JANUS:
- JUICE: mission to Jupiter in development
- Japan:
- Japan Aerospace Exploration Agency (JAXA): Japan agency includes astronomical research
- Japanese:
- AKARI: Japanese space infrared telescope
- ASTRO-H: Japanese space x-ray telescope
- MAXI: Japanese X-ray camera on the International Space Station
- SELENE: 2007-2008 Japanese lunar probe
- Yohkoh: 1990s Japanese solar observatory spacecraft
- JAXA:
- JCM:
- JCMT:
- JD:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- JDEM:
- WFIRST: proposed space observatory
- JDN:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Jeans Criterion:
- Jeans Length: critical radius below which gravity will collapse a cloud
- Jeans Density:
- Jeans Length: critical radius below which gravity will collapse a cloud
- Jeans Instability:
- Jeans Length: critical radius below which gravity will collapse a cloud
- Jeans Length: critical radius below which gravity will collapse a cloud
- Jeans Mass:
- Jeans Length: critical radius below which gravity will collapse a cloud
- JEDI:
- JEM-X:
- INTEGRAL: European gamma ray observatory-satellite
- Jet: stream of matter from an astronomical body
- 3C 273: first quasar discovered
- 3C 303: Seyfert galaxy
- 3C 9: first quasar discovered
- Cygnus A (3C 405,QSO B1957+405): early-discovered radio galaxy and quasar
- M87: supergiant elliptical galaxy
- Superrotating Wind: wind traveling in the same direction as the planet is rotating
- Zonal Flow: east-west air circulation
- Zone: apparent "horizontal" band in an atmosphere
- Jet Current: electric current within a plasma jet
- Jet Stream:
- Jet: stream of matter from an astronomical body
- Superrotating Wind: wind traveling in the same direction as the planet is rotating
- Thermal Wind: wind from pressure and the Coriolis force varying with altitude
- Zonal Flow: east-west air circulation
- jets:
- JHK:
- JHK Photometric System (JHK): system to classify stars according to near-infrared colors
- JIRAM:
- Jodrell Bank Mark II:
- Mark II (MKII): 38m radio telescope in England
- Jodrell Bank Observatory:
- Mark II (MKII): 38m radio telescope in England
- John A. Galt Telescope:
- Johnson System:
- Johnson-Cousins System:
- Johnson-Morgan System:
- Johnson-Nyquist Noise:
- Thermal Noise: noise inherent in electronic component warmer than absolute zero
- JOI:
- Joint Dark Energy Mission:
- WFIRST: proposed space observatory
- Joule: SI unit of energy
- journal:
- Jovian Planet:
- JPL:
- JUICE: mission to Jupiter in development
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Julian Day:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Julian Day Number:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Julian Year:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Juno: mission to Jupiter
- Juno Orbit Insertion:
- JunoCam:
- Jupiter: largest planet in the solar system
- Callisto: well-known Jupiter moon
- Europa: well-known Jupiter moon
- Europa Clipper: planned Europa space probe
- Galileo: space mission to Jupiter
- Ganymede: well-known Jupiter moon
- Helium Rain: possible source of heat in giant planet atmospheres
- Io: well-known Jupiter moon
- JUICE: mission to Jupiter in development
- Juno: mission to Jupiter
- Liquid Planet: planet consisting of liquid
- Shepherd Moon: small moon at outer edge of a ring
- Voyager: space probes to observe planets and the edge of the solar system
- Jupiter I:
- Io: well-known Jupiter moon
- Jupiter Icy Moons Explorer:
- JUICE: mission to Jupiter in development
- Jupiter II:
- Europa: well-known Jupiter moon
- Jupiter III:
- Jupiter IV:
- Jupiter Trojan:
- Jupiters:
- JVLA:
- JWST:
- Jy:
- Jansky (Jy): unit of measurement of spectral flux density
- K:
- Boltzmann Constant (k): relates particle energy with temperature
- K Band: infrared passband centered around 2.2 microns, or 136 THz
- K-Type Star (K): type of star with about 3/4 the mass of the Sun
- King Catalog: list of 21 open clusters
- Love Number: measures of rigidity of a body
- Permeability (κ,k): ability of a material to allow fluids to pass through it
- K Band: infrared passband centered around 2.2 microns, or 136 THz
- K Belt:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- K Belt Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- K Correction: correction to magnitude for redshift
- K Dwarf:
- M Dwarf: small, cool main-sequence star in stellar class M
- Red Dwarf: small, cool main-sequence star
- K line:
- Calcium (Ca): element, Ca, atomic number 20
- K-band Multi-Object Spectrograph:
- KMOS: 2-micron spectrograph on ESO VLT
- K-Class:
- K-Type Star (K): type of star with about 3/4 the mass of the Sun
- K-Type Star (K): type of star with about 3/4 the mass of the Sun
- K2: second kepler mission working around failed equipment
- KAGRA: pair of interferometers to detect gravitational waves
- Kaguya:
- SELENE: 2007-2008 Japanese lunar probe
- Kaiser Distortion:
- KAIT:
- Kamioka Gravitational Wave Detector:
- KAGRA: pair of interferometers to detect gravitational waves
- KAO:
- Kapteyn Universe: early 20th century model of the universe centered on the Milky Way
- Kapteyn's Star: nearby mdwarf
- Karl G. Jansky Very Large Array:
- Karoo Array Telescope:
- MeerKAT: new radio telescope in South Africa
- KAT:
- MeerKAT: new radio telescope in South Africa
- KAT-7:
- MeerKAT: new radio telescope in South Africa
- Katalog von 1053 staerker bewegten Fixsternen:
- Katzman Automatic Imaging Telescope:
- KB:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- KB Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- KBO:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Plutoid: Pluto-like dwarf planet
- KE:
- Keck:
- Keck Interferometer:
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Keck Planet Finder (KPF): spectrograph in development for Keck
- Keck Planet Imager And Characterizer (KPIC): proposed noise-reducing planet imager for Keck
- KELT: pair of telescopes to search for transients
- KELT-North:
- KELT: pair of telescopes to search for transients
- KELT-South:
- KELT: pair of telescopes to search for transients
- Kelvin Time:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Kelvin-Helmholtz Mechanism: release of energy from gravitational collapse
- Kelvin-Helmholtz Timescale:
- Kennicutt-Schmidt Law: relation between gas density and star formation rate
- Kennicutt-Schmidt Relation:
- Kepler:
- Kepler Dichotomy:
- Kepler Input Catalog:
- Kepler Object Of Interest:
- Kepler Orbit:
- Kepler Radius: radius at which a particular velocity would orbit
- Kepler Radius Distribution:
- Kepler Telescope: space telescope watching stars for exoplanets
- Kepler's Laws: laws of the kinematics of orbits
- Kepler's Laws Of Planetary Motion:
- Keplerian Disk: disk whose motion follows Kepler's laws
- Keplerian Orbit: orbit following a perfect ellipse or other conic section
- Keplerian Radius:
- Kerberos:
- Pluto: dwarf planet formerly listed as one of the nine planets
- KH Mechanism:
- KH Timescale:
- KI:
- Kibel Number:
- KIC:
- KiDS:
- Kilo-Degree Survey:
- Kilodegree Extremely Little Telescope:
- KELT: pair of telescopes to search for transients
- Kilometer Size Barrier: a barrier to accretion on the order of a kilometer diameter
- Kilonova: explosive event larger than a nova and smaller than a supernova
- Kinematic Distance: distance to objects within Milky Way based on radial velocity
- Kinematic Distance Ambiguity:
- Kinematic Sunyaev-Zel'dovich Effect:
- kinematics:
- Kinetic Energy (KE): an object's energy due to its motion
- Kinetic Equilibrium:
- Kinetic Temperature:
- Kinetic Theory Of Gases:
- Cross Section: "area" representation of probability of an interaction of particles
- King:
- King Catalog: list of 21 open clusters
- Kirchhoff Diffraction Formula:
- Kirchhoff's Laws: laws regarding the source of spectral lines
- Kirchhoff's Three Laws Of Spectroscopy:
- Kirkwood Gap: gaps in asteroid orbital radii corresponding to Jupiter resonances
- Kiso Observatory:
- Kiso Survey of Ultraviolet Excess Galaxies (KUG): 1980 Japanese survey
- Kitt Peak:
- Kitt Peak 4m:
- Kitt Peak National Observatory:
- KMOS: 2-micron spectrograph on ESO VLT
- KMOS3D: survey of galaxies before to after peak star formation
- KOALA:
- KOI:
- Kolmogorov Energy Spectrum:
- Kolmogorov Spectrum: energy spectrum of the eddies of different sizes in a turbulent fluid
- Konkoly Observatory:
- HATNet: distributed array of telescopes to search for transients
- Korean Solar Radio Burst Locator:
- Korsch Telescope: type of reflecting telescope
- Kowal's Object:
- Kozai Cycle:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- Kozai Oscillation:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- Kozai-Lidov Oscillation:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- kpc:
- Parsec (pc): about 3.26 light-years
- KPF:
- KPIC:
- KPNO:
- KPNO 4m:
- Kramers' Law:
- Kramers' Opacity Law: opacity's relation to density and temperature
- Krylov Subspace:
- Krylov Subspace Method: efficient method of numerically solving sets of linear equations
- KSRBL:
- kSZ:
- kSZE:
- KU-BAND:
- Kueyen Telescope:
- KUG:
- Kuiper Airborne Observatory (KAO): infrared observatory-plane in the 1980s
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Kuiper Belt Object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Plutoid: Pluto-like dwarf planet
- L:
- L Band:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- L Dwarf:
- Brown Dwarf (BD): star-like object with less mass than a star
- L-Type Star (L): type of star cooler than an M-type star
- L'Institute Canadian d'astrophysique théorique:
- L-Class:
- L-Type Star (L): type of star cooler than an M-type star
- L-point:
- L-Type Star (L): type of star cooler than an M-type star
- L1:
- L1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- L2:
- L3:
- L4:
- L5:
- L500:
- La Silla Observatory:
- LABOCA:
- LABOCA ECDFS Submillimeter Survey:
- LABOCA ECDFS Submm Survey:
- LABOCA Extended Deep Field South Submillimetre Survey (LESS): submillimeter survey of a well-studied piece of sky
- Lac 9352:
- Lacaille 9352: red dwarf that is the tenth nearest star system
- LAE:
- Laevens 2:
- Lagrange Point:
- Lagrange Stability: a quality of some stable orbits
- Lagrangian Code:
- Lagrangian Libration Point:
- Lagrangian Point: points around two orbiting bodies where small objects sit
- Lalande 21185: nearby red dwarf
- LAMBDA: NASA archive center re CMB data
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- Laminar Flow:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LAMOST Experiment for Galactic Understanding and Evolution:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LAMP:
- Landau-Oppenheimer-Volkoff Limit:
- Lane-Emden Equation: form of equation of state for gas ball in hydrostatic equilibrium
- Laniakea:
- Laniakea Supercluster: group of clusters including the Local Group
- Laplace Radius (rL): a radius for a stable orbit of a satellite around a planet
- Laplace Spherical Harmonics:
- Laplace's Equation:
- Laplace-Lagrange Secular Evolution Theory:
- Laplace-Lagrange Secular Theory: theory of evolution of planetary orbits
- Large Altazimuth Telescope (BTA-6): 6 meter reflector telescope in Russia
- Large Binocular Telescope (LBT): dual 8.4 meter telescope in Arizona
- Large Binocular Telescope Interferometer:
- Large Magellanic Cloud (LMC): irregular satellite galaxy of the Milky Way
- Large Millimeter Telescope (LMT): large microwave telescope in Mexico
- Large Scale Cryogenic Gravitational Wave Telescope:
- KAGRA: pair of interferometers to detect gravitational waves
- Large Scale Streaming Motion:
- Large Scale Structure (LSS): the universe's structure as in placement of clusters
- Large Scale Structure Of The Universe:
- large scale structures:
- Galaxy Bias: degree to which galaxy density fails to correspond to dark matter density
- Supercluster: cluster of galaxy clusters
- Void: empty spaces between large scale structures
- Large Sky Area Multi-Object Fibre Spectroscopic Telescope:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- Large Strategic Science Missions:
- NASA: includes space-based astronomy research
- Large Synoptic Survey Telescope (LSST): 8-meter survey reflecting telescope under construction in Chile
- Large UV/Optical/Infrared Surveyor:
- LUVOIR: plan for a space-based 10 meter telescope
- Large Zenith Telescope (LZT): 6 meter liquid mirror telescope in British Columbia
- Las Campanas Observatory:
- Las Cumbres Observatory (LCO): world-wide network of telescopes
- LASCO:
- LasDamas: simulations of large scale evolution of dark matter and galaxies
- Laser:
- Coherent Light: beam of light at a single frequency
- Emission: addition of photons to a beam of EMR
- Virgo: ground-based gravitational-wave detector in Italy
- Laser Interferometer Gravitational-Wave Observatory:
- LIGO: pair of observatories to detect gravitational waves
- Laser Interferometer Space Antenna:
- LISA: proposed space mission to detect gravitational waves
- LASS:
- HEAO-1: 1977 x-ray observatory space mission
- Last Parsec Problem:
- LAT:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- LAT All-Sky Survey:
- Fermi (FGST,GLAST): satellite for studying gamma-rays
- Late:
- Late Heavy Bombardment (LHB): time after solar system planet-formation when many impacts occurred
- Late-Type Galaxy:
- Galaxy: gravitationally-bound group of stars
- Latent Heat:
- Latitude:
- Law of Cosmic Censorship: a singularity cannot be observed
- Law of Gravitation:
- Law Of Refraction:
- LBC:
- LBG:
- LBN:
- LBT:
- LBTI:
- LBTI/LMIRCAM:
- LBTI/NOMIC:
- LCDM:
- Lambda-CDM model (ΛCDM,LCDM): big-bang cosmological model with a cosmological constant and cold dark matter
- LCGT:
- KAGRA: pair of interferometers to detect gravitational waves
- LCO:
- LCROSS: space probe observing the lunar poles
- LDN:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- LDSS3:
- Leakage Neutron:
- LECP:
- Voyager: space probes to observe planets and the edge of the solar system
- LEDA:
- Left-hand Circular Polarization:
- Polarization: property of waves that oscillate in a particular direction
- Legacy Archive for Microwave Background Data Analysis:
- LAMBDA: NASA archive center re CMB data
- Legendre Polynomials: useful sequence of polynomials
- Lego Principle: principle that life is associated with a skew in molecule abundances
- LEGUE:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LEND:
- Length Contraction:
- Lensing Deflection Field:
- Lensing Map:
- Lenslet Array:
- Lensmaker's Equation:
- Lensmaker's Formula:
- Lenticular Galaxy:
- Leo Cluster:
- Lepton:
- Baryon: protons, neutrons, and other three-quark particles
- Particle: very small thing
- LESS:
- LETGS:
- LF:
- Luminosity Function (LF): function giving number of stars or galaxies at different luminosities
- LF Radio Astronomy:
- LFAA:
- LFC:
- LFI:
- Planck: microwave telescope in space
- LG:
- Local Group (LG): group of galaxies including the Milky Way
- LGM-1:
- Pulsar (PSR): astronomical body whose electromagnetic radiation displays a cycle
- LGRB:
- LHB:
- LHCP:
- Polarization: property of waves that oscillate in a particular direction
- LHO:
- LIGO: pair of observatories to detect gravitational waves
- LHS:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- LHS 1140b:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- Li:
- Lithium (Li): metal, Li, atomic number 3
- Libration: oscillating motion of orbiting bodies relative to each other
- Libration In Latitude:
- Libration: oscillating motion of orbiting bodies relative to each other
- Libration In Longitude:
- Libration: oscillating motion of orbiting bodies relative to each other
- Libration Point:
- Lagrangian Point: points around two orbiting bodies where small objects sit
- Libration: oscillating motion of orbiting bodies relative to each other
- Lick 3m:
- Lick Observatory:
- Lick Observatory and Tenegra Observatory Supernova Searches:
- Lick Observatory Calcium Line Survey (LkCl): 1980s survey of T-Tauri Stars in the Taurus-Auriga Complex
- Lick Observatory Supernova Search (LOSS): search for supernovae for cosmological study
- Lidov-Kozai Effect:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- Lidov-Kozai Mechanism:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- Lie Group:
- Lie Transform: type of infinitesimal transform
- life:
- Light:
- Light Cone: region of space-time which you can see or can see you
- Light Curve: changing intensity of light from a transient
- Light Cylinder:
- Light Nebula:
- Light satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection:
- LiteBIRD: proposed spacecraft to map CMB polarization
- Light-Year:
- Parsec (pc): about 3.26 light-years
- LIGO: pair of observatories to detect gravitational waves
- LIGO A+:
- LIGO: pair of observatories to detect gravitational waves
- LIGO H:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Hanford Observatory:
- LIGO: pair of observatories to detect gravitational waves
- LIGO L:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Livingston Observatory:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Voyager:
- LIGO: pair of observatories to detect gravitational waves
- LIGO-India: planned gravitational wave detector in India
- Limb:
- Limb Darkening: the darkening of edge of a body such as the Sun
- limit:
- LINC/Nirvana:
- Lincoln Laboratory.:
- LINEAR: survey of near-Earth objects
- Lincoln Near-Earth Asteroid Research:
- LINEAR: survey of near-Earth objects
- Lindblad Resonance:
- Lindblad Torque: torque due to Lindblad resonances
- line:
- 21cm Line: hydrogen line useful for determining redshift
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- Lyman Alpha (Ly-α,Lyα): first line in the Lyman series
- Line Blanketing: so many bunched spectral lines that they cannot be distinguished
- Line Broadening: processes causing a spectral line to have width
- Line Depth:
- Line Intensity Mapping:
- line of beta stability:
- Line Of Nodes:
- Line Profile:
- line series:
- Balmer Series: hydrogen lines for electrons settling from n > 2 to n = 2
- Brackett Series: hydrogen lines for electrons settling from n > 4 to n = 4
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Oxygen Lines: spectral lines specific to oxygen
- Paschen Series: hydrogen lines for electrons settling from n > 3 to n = 3
- Water Lines: spectral lines specific to water
- Line Shape:
- Line Shape Function: function describing the shape of a spectral line
- Line-Blanketing Effect:
- Line Blanketing: so many bunched spectral lines that they cannot be distinguished
- LINEAR: survey of near-Earth objects
- Linear Algebra:
- Linear Polarization:
- Polarization: property of waves that oscillate in a particular direction
- Linear System:
- Linear Theory: theory of operators satisfying the property of superposition
- Linear Theory: theory of operators satisfying the property of superposition
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- LINER Galaxy:
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- lines:
- Lipid:
- Lego Principle: principle that life is associated with a skew in molecule abundances
- liquid mirror:
- Liquid Mirror Telescope: reflecting telescope with primary mirror formed of spinning liquid
- Liquid Planet: planet consisting of liquid
- Liquid Water Habitable Zone:
- Liquid Water Zone:
- LIRG:
- LIRIS:
- LISA: proposed space mission to detect gravitational waves
- LISA Pathfinder:
- LISA: proposed space mission to detect gravitational waves
- LiteBIRD: proposed spacecraft to map CMB polarization
- Lithium (Li): metal, Li, atomic number 3
- Littrow:
- LK Oscillation:
- Kozai Mechanism: an effect on an orbit by another, more distant orbiting body
- LkCl:
- Llano de Chajnantor Observatory:
- LLO:
- LIGO: pair of observatories to detect gravitational waves
- LMC:
- LMI:
- LMT:
- Lobe:
- local:
- Local Bubble:
- Local Group (LG): group of galaxies including the Milky Way
- Local Sheet: flat group of galaxies around the Local Group
- Local Standard of Rest (LSR): velocity with respect to our region of the Milky Way
- Local Supercluster:
- Local Thermodynamic Equilibrium (LTE): state where temperature variation is too small to matter
- Local Void: void next to the Local Group
- Local Volume (LV): region around the Local Group
- Locally Brightest Galaxy:
- location:
- Lockman Cloud:
- Smith Cloud: high-velocity cloud on collision course with Milky Way
- Lockman Hole: region of sky with little Milky Way neutral hydrogen
- LOFAR:
- LOFAR Prototype Station:
- LOPES: cosmic ray detector that detected resulting radio
- LOFAR Two-metre Sky Survey:
- LOFAR-Core:
- logarithmic:
- LOLA:
- LONEOS: survey of near-Earth objects
- Long Gamma Ray Burst:
- Gamma-Ray Burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Long Period Comet:
- Oort Cloud: cloud of comets and minor planets around the solar system
- Long Rossby Wave:
- Kelvin Waves: pressure and gravity waves formed by Coriolis Force and a barrier
- Longitude Of Ascending Node:
- Lookback Time:
- LOPES: cosmic ray detector that detected resulting radio
- Lorentz Drag:
- Lorentz Factor:
- Lorentz Force: force on a point charge due to magnetic fields
- Lorentz Invariance:
- Lorentz Transform:
- Lorentz Transformation: equations describing the effect of relative motion on length and velocity
- Lorenz Transform:
- Relativity: physics models accommodating the constancy of the speed of light
- LORRI:
- LOSS:
- LOTOSS:
- LoTSS:
- LOV:
- Love Number: measures of rigidity of a body
- Love-Shida Number:
- Lovell Telescope:
- Lovell Transit Telescope:
- Low Frequency Aperture Array:
- Low Frequency Radio Astronomy: astronomy using the lower end of the radio spectrum
- Low Mass Star: stars of less than half the solar mass
- Low Resolution Spectrograph.:
- HRS: high resolution spectrography
- Low Resolution Spectrography:
- HRS: high resolution spectrography
- Low-Frequency Array (LOFAR): low frequency radio telescope
- Low-ionization Nuclear Emission-Line Region:
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- Low-Surface-Brightness Galaxy (LSB Galaxy): galaxies less bright than those historically identified
- Lowell Observatory:
- Lowell Observatory Near-Earth-Object Search:
- LONEOS: survey of near-Earth objects
- Lowmass Star:
- LRG:
- LRIS:
- LRO:
- LROC:
- LRS:
- LRS2:
- LS:
- LSB Galaxy:
- LSC:
- LSR:
- LSR Velocity:
- LSS:
- LSST:
- Lsun:
- Sun: star at center of solar system
- LTE:
- LTG:
- Galaxy: gravitationally-bound group of stars
- LUCI:
- Lucky Exposures:
- Lucky Imaging: method of combining short-term images to yield better resolution
- Lucky Imaging: method of combining short-term images to yield better resolution
- Luhman 16: nearby binary brown dwarf
- Luminosity (L): measure of brightness
- Luminosity Class: classification of size/luminosity of stars
- Luminosity Density: luminosity per unit volume
- Luminosity Distance (dL, DL): distance to an object based upon the distance's effect on received flux
- Luminosity Equation:
- Luminosity Function (LF): function giving number of stars or galaxies at different luminosities
- Luminous Infrared Galaxy (LIRG): a galaxy emitting a lot of far-infrared light
- Luminous Red Galaxy (LRG): distant bright red galaxies in the Sloan Digital Sky Survey
- Luminous Supergiant:
- Lunar Cold Trap:
- Moon: Earth's natural satellite
- Lunar Crater Observation and Sensing Satellite:
- LCROSS: space probe observing the lunar poles
- Lunar Reconnaissance Orbiter (LRO): space probe orbiting the Moon
- Lunar Swirl: swirly spot on the surface of the Moon
- Lupus:
- Lupus Transit Survey: survey for hot Jupiters in a region of constellation Lupus
- LUVOIR: plan for a space-based 10 meter telescope
- Luyten 726-8: nearby binary star system
- Luyten Half-Second Catalog (LHS): 1979 catalog of 4000 stars with high proper motion
- LV:
- LWCam:
- CCAT: 25 meter submillimeter telescope planned for Chile
- LWP:
- LWR:
- LWS:
- Lyα:
- Lyman Alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Ly-α:
- Lyman Alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyapunov Exponent:
- Lyapunov Time: timescale over which a dynamical system is chaotic
- Lyapunov Time: timescale over which a dynamical system is chaotic
- Lyman:
- Lyman Alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman Alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman-Alpha Emitter (LAE): redshifted galaxy emitting the Lyman alpha line
- Lyman-Alpha Forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- Lyman Band:
- Lyman Limit:
- Lyman Lines:
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman Series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman-Alpha Emitter (LAE): redshifted galaxy emitting the Lyman alpha line
- Lyman-Alpha Emitting Galaxy:
- Lyman-Alpha Forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- Lyman-Break Galaxy (LBG): a galaxy emitting very little shorter than 912 angstroms
- Lyman-Werner Photon: ultraviolet photon with proper energy to excite molecular hydrogen
- Lynds 1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Lynds Bright Nebula Catalog (LBN): 1950s/1960s list of bright nebulae found on Palomar plates
- Lynds Catalog of Dark Nebulae (LDN,L): 1950s/1960s list of dark nebulae found on Palomar plates
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Lynx-Ursa Major Filament:
- Lyon Observatory:
- Lyon-Meudon Extragalactic Database:
- LZT:
- M:
- M Band:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- M Dwarf: small, cool main-sequence star in stellar class M
- Brown Dwarf (BD): star-like object with less mass than a star
- M-Type Star (M): type of star with a temperature in the vicinity of 2500K
- M-Class:
- M-Type Star (M): type of star with a temperature in the vicinity of 2500K
- M-Type Star (M): type of star with a temperature in the vicinity of 2500K
- m.f.u.:
- Jansky (Jy): unit of measurement of spectral flux density
- M/L:
- M1:
- M100:
- Messier 100 (M100,NGC 4321): easily observed spiral galaxy
- M101:
- M20:
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- M31:
- Andromeda (M31): spiral galaxy in the Local Group
- HBK: study of M31 globular clusters
- PAndAS: survey of M31 and M33
- POINTE-AGAPE: survey of M31 for microlensing
- SKHB: survey of globular clusters in M31
- M33:
- M42:
- Orion Nebula (M42, NGC 1976): easily observed nebula that includes SF regions
- M51:
- M51a:
- M64:
- M74:
- Messier 74 (M74,NGC 628): easily observed spiral galaxy
- M81:
- M82: nearby starburst galaxy
- M83:
- M87: supergiant elliptical galaxy
- M94:
- M20:
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- M500:
- Mbol:
- ms:
- Mach Angle:
- Expansion Fan: the "sound" of a supersonic flow flowing around a convex corner
- Mach Number: ratio of a flow with the speed of sound
- machine learning:
- MACHO: proposed astronomical objects comprising dark matter
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- MACHOs:
- EROS: search for MACHOs
- GMAN: automated survey to identify microlensing transients
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- OGLE: survey searching for microlensing transients
- POINTE-AGAPE: survey of M31 for microlensing
- Macquarie/AAO/Strasbourg Hα Planetary Galactic Catalog:
- Macronova:
- Kilonova: explosive event larger than a nova and smaller than a supernova
- MACS:
- MAESTRO:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Maffei 1:
- Council Of Giants: twelve large galaxies surrounding the Local Group
- IC 342: spiral galaxy in the Council of Giants
- Maffei 2:
- MAG:
- MAG/ER:
- MagAO:
- MagE:
- Magellan Planet Search Program:
- Magellan Telescopes: pair of 6.5m optical telescopes in Chile
- Magellanic Clouds:
- Magellanic Clouds Photometric Survey (MCPS): UBVI survey of the Magellanic Clouds
- Magellanic Spiral Galaxy:
- Magellanic Stream:
- MagIC: numerical code to for fluid dynamics including dynamos
- Magma Ocean: presumed to occur early in Earth history and potentially on exoplanets
- Magnesium:
- Magnetar: neutron star with a strong magnetic field
- Magnetic Anomaly: variation in a body's magnetic field
- Magnetic Arcade: series of arch-like magnetic flux lines on the Sun
- Magnetic Dipole Radiation: EMR naturally generated by a spinning magnetic dipole
- Magnetic Dynamo:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Magnetic Energy:
- Magnetic Energy Density:
- Magnetic Energy Spectrum: spatial spectral density of the energy associated with magnetic fields
- Magnetic Field: magnetic force as distributed over a space
- Magnetic Field Intensity:
- Magnetic Field Strength (H): a field associated with magnetism
- Magnetic Flux (B): total magnetism passing through a surface
- Magnetic Flux Density (B): vector field describing magnetism in relation to the Lorentz force
- Magnetic Induction: voltage across a conductor induced by changing magnetic field
- Magnetic Monopole:
- Magnetic Permeability:
- Permeability (κ,k): ability of a material to allow fluids to pass through it
- Magnetic Power Spectrum:
- Magnetic Pressure:
- Magnetic Quantum Number:
- Magnetic Reconnection: change in magnetic topology within a fluid
- Magnetic Reynolds Number:
- Reynolds Number (Re): measure reflecting a fluid system's propensity to turbulence
- magnetism:
- Magnetized Molecular Cloud:
- Magnetizing Field:
- Magneto-Brems:
- Magneto-Bremsstrahlung:
- Magneto-Plasma System:
- Magnetoacoustic Wave:
- Magnetobremsstrahlung:
- Magnetohydrodynamics (MHD): dynamics of electrically conducting fluids
- Magnetometer: instrument to measure the strength of a magnetic field
- Magnetorotational Instability (MRI): instability in the fluid of a disk from MHD effects
- Magnetosonic Wave: a type of sonic wave in a plasma
- Magnetosphere: area around an object where its magnetic field dominates
- DQ Tau: young binary star system
- Magnetospheric Truncation Radius: radius at which the disc ram pressure matches the magnetic field pressure
- Magnification:
- Magnitude: a logarithmic measure of brightness
- Magnitude-redshift relation:
- MAIA:
- Main Asteroid Belt:
- Main Belt:
- Main Belt Asteroid:
- Main Sequence:
- Main Sequence Fitting: cluster star distance determined through fitting with the H-R diagram
- Main Sequence Galaxy:
- Main Sequence Star: star burning hydrogen into helium
- Main-sequence Turn-off Point:
- Turn-off Point (TO): point in H-R diagram of a cluster where stars turn red
- MAJIS:
- JUICE: mission to Jupiter in development
- Major Merger:
- Makemake:
- Malmquist Bias: selection bias from detecting only the brighter objects
- MaNGA:
- MANIFEST:
- MAP:
- MARCI:
- MARDI:
- Phoenix: Mars probe launched by NASA in 2007 with lander
- Mariner:
- Mars: well-explored planet in the solar system
- Mariner 10:
- Mercury: inner-most and smallest planet in the solar system
- Mark:
- Mark II (MKII): 38m radio telescope in England
- Markarian:
- Markarian Galaxy (Mkn): list of galaxies with excess ultraviolet light
- Markov Chain:
- Markov Chain Monte Carlo (MCMC): model technique to approximate multi-dimensional integrals
- Mars: well-explored planet in the solar system
- Mars 2020: Mars rover in planning
- Mars: well-explored planet in the solar system
- Mars 2020 Rover:
- Mars Express: Mars probe launched by ESA in 2003
- Mars Global Surveyor (MGS): Mars probe launched by NASA in 1996
- Mars Phoenix:
- Phoenix: Mars probe launched by NASA in 2007 with lander
- Mars Reconnaissance Orbiter (MRO): Mars probe launched by NASA in 2005
- Mars: well-explored planet in the solar system
- Mars Weather Research and Forecasting Model:
- MarsWRF: Mars-oriented general circulation model
- MARSIS:
- MarsWRF: Mars-oriented general circulation model
- MARVELS:
- MARVELS Spectrograph:
- MASCARA: distributed array of telescopes to search for exoplanets
- Maser: electromagnetic radiation amplified by stimulated emission
- Maser Emission:
- Maser: electromagnetic radiation amplified by stimulated emission
- masers:
- Hydroxyl (OH): compound of hydrogen and oxygen, one atom each
- OH/IR Source: AGB star with strong OH maser
- MASH Catalog of Planetary Nebulae: 995 possible planetary nebulae
- MASPEX:
- Mass:
- Mass Conservation Equation:
- Mass Continuity Equation:
- Mass Density: density of a volume of space
- Mass Extinction: event in which many species went extinct
- Mass Fraction: measures of star's constituents
- Mass Function: measure of binaries that constrains the masses
- Mass Loading: moving gas gaining mass from clouds or stars
- Mass Loss: a star's reduction in mass
- Mass Number:
- Fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- Isotope: subclass of an element with a specific number of nucleons
- Radioactive Decay: changes in atomic nuclei that happen over time
- Mass Ratio:
- Mass Shell: conceptual volume of mass shaped like a hollow sphere
- Mass Spectrograph:
- Mass Spectrometer: device to determine the mass of molecules in a mixture
- Spectrometer: device to measure light by wavelength across its spectrum
- Mass Spectrometry:
- Mass Spectrometer: device to determine the mass of molecules in a mixture
- Spectrometry: measuring the strengths of different electromagnetic wavelengths
- Mass Transport: transfer of mass from one part of a body/disk to another
- Mass-Luminosity Relation: model relating stellar mass and luminosity
- Mass-Metallicity Relation:
- Mass-Radius Relation: model relating stellar mass and radius
- Mass-Radius Relationship:
- Mass-To-Light Ratio (M/L,ϒ): measure of a population of stars or region
- Massive Astrophysical Compact Halo Object:
- MACHO: proposed astronomical objects comprising dark matter
- Massive Cluster Survey (MACS): survey of distant clusters evident in ROSAT X-ray data
- Massive Compact Halo Object:
- MACHO: proposed astronomical objects comprising dark matter
- MAST: archive of data from surveys and missions
- Mastcam-Z:
- materials:
- mathematics:
- MATISSE:
- matrix:
- Matter Era:
- Radiation Era: early universe era when radiation pressure dominated
- Matter Power Spectrum:
- Matter Waves:
- Matter-Antimatter Asymmetry:
- Antimatter: similar to normal matter but with opposite electrical charge
- Matter-Dominated Era:
- Radiation Era: early universe era when radiation pressure dominated
- Mauna Kea: Hawaiian mountain, the site of observatories
- Mauna Kea Observatories (MKO): observatories on Mauna Kea in Hawaii
- Mauna Kea: Hawaiian mountain, the site of observatories
- Max Planck Institute for Astronomy (MPIA): Heidelberg research institute
- Max Planck Institute for Radio Astronomy (MPIR): Bonn research institute
- Max Planck Society:
- Max Wolf's Catalog of Stars With Proper Motion: early 20th century catalog of 1500 stars
- MAXI: Japanese X-ray camera on the International Space Station
- Maximum Accretion Rate:
- Accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- Maximum Iron Fraction: derived from planet-formation models
- Maximum Likelihood Estimation:
- Maximum Likelihood Mapmaking: method of making maps using varying data
- Maxwell:
- Gauss (G,Gs): measurement of magnetic field β
- Magnetic Flux (B): total magnetism passing through a surface
- Maxwell's Equations: four equations describing electricity and magnetism
- Maxwell-Boltzmann Distribution: distribution of velocities of gas particles
- Maxwell-Faraday Equation:
- Mayall 4m Telescope: 4m reflector telescope at Kitt Peak
- Mazurek's Law: tweaking parameters is canceled by feedback
- MB20:
- MBA:
- MBAC:
- MBJD:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Mbol:
- MBS:
- MC:
- HEAO-1: 1977 x-ray observatory space mission
- MCAL:
- AGILE: Italian space gamma-ray observatory
- McDonald Observatory:
- Hobby-Eberly Telescope (HET): 9.2 meter telescope in Texas
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- MCG:
- MCINN:
- MCMC:
- MCPS:
- MCS:
- MDI:
- MDR:
- MDR/SRR: planning step for a NASA mission
- MDR/SRR: planning step for a NASA mission
- Mean Free Path: average length that a particle travels before interaction
- Mean Intensity:
- Intensity: power reaching a surface from a specific source
- Mean Molecular Weight (μ): measurement of a gas usual for approximating in gas models
- Mean Motion Resonance:
- Orbital Resonance: orbits of multiple bodies that align from periodic gravitational interaction
- Mean-Field Dynamo Theory:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Mean-Field MHD:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- MEarth:
- MEarth Project (MEarth): automated observatory for spotting changes in light from red dwarf stars
- measure:
- measurement:
- Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanet host Stars:
- MUSCLES: HST UV survey of some M-Dwarfs that host exoplanets
- MECA:
- Phoenix: Mars probe launched by NASA in 2007 with lander
- mechanics:
- mechanisms:
- MEDA:
- Medicina Radio Observatory:
- medium:
- Cosmic Dust: cosmic dust is dust in space such as interstellar dust
- Medium Band Photometric System:
- Medium-Class Explorers Program:
- FINESSE: planned space mission for exoplanet spectrography
- NASA: includes space-based astronomy research
- MeerKAT: new radio telescope in South Africa
- MeerKAT Precursor Array:
- MeerKAT: new radio telescope in South Africa
- MeerLICHT: South African telescope to coordinate with MeerKAT
- Mega-Earth: rocky planet ten times the size of Earth
- MegaCam:
- Megaflare:
- Megajansky:
- Jansky (Jy): unit of measurement of spectral flux density
- MegaPrime:
- MEGARA:
- Mel:
- MELACOM:
- Melipal Telescope:
- Melotte:
- Melotte 25:
- Melotte Catalog: 1915 catalog of open and globular clusters
- Memory Burst:
- Mercator Telescope: 1.2m telescope in the Canary Islands
- HERMES: four-channel spectrograph on the Anglo-Australian Telescope
- Mercury: inner-most and smallest planet in the solar system
- Merger:
- mergers:
- Final Parsec Problem: lack of a convincing theory on how SMBHs can reach each other
- Galaxy Merger: combination of galaxies upon collision
- Gini/M20: an automatable method of detecting whether a galaxy has recently merged
- PCA Analysis: an automatable method of determining galaxy morphology
- Tidal Arm: arm of gas and potentially stars leading from a galaxy
- Tidal Tail: string of mass ejected by a tidal forces in a neutron star merger
- Meridian: circle around the Earth passing through both poles
- Meridional Current:
- Meridional Flow: north-south air circulation
- MEROPE:
- Meson:
- Baryon: protons, neutrons, and other three-quark particles
- Particle: very small thing
- Mesopause:
- Mesosphere:
- MESSENGER:
- Mercury: inner-most and smallest planet in the solar system
- Messier 1:
- Messier 100 (M100,NGC 4321): easily observed spiral galaxy
- Messier 31:
- Andromeda (M31): spiral galaxy in the Local Group
- Messier 33:
- Messier 74 (M74,NGC 628): easily observed spiral galaxy
- Messier 82:
- M82: nearby starburst galaxy
- Messier 87:
- M87: supergiant elliptical galaxy
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- Messier Objects:
- Messier Catalog: catalog of astronomical objects to avoid when looking for comets
- Metal: in astrophysics, any element more massive than helium
- Calcium (Ca): element, Ca, atomic number 20
- Carbon (C): element, C, atomic number 6
- Iron (Fe): metal, Fe, atomic number 26
- Lithium (Li): metal, Li, atomic number 3
- Metallicity (Z): metal fraction of an object
- Nickel (Ni): metal, Ni, atomic number 28
- Nitrogen (N): metal, N, atomic number 7
- Oxygen (O): element, O, atomic number 8
- Silicon (Si): metal, Si, atomic number 14
- Sodium (Na): metal, Na, atomic number 11
- Sulfur (S): metal, S, atomic number 16
- Metal Abundance:
- Metal-Free Stars:
- Metal-Poor Stars:
- Metal-Rich Stars:
- Metallic Helium:
- Metal: in astrophysics, any element more massive than helium
- Metallic Hydrogen:
- Metal: in astrophysics, any element more massive than helium
- metallicity:
- metals:
- Alpha Capture: combination of a nucleus and an incoming alpha particle
- Alpha Element: element created by alpha capture
- Alpha Process: synthesization of elements through alpha capture
- Iron Peak: relatively high abundance of iron and nearby elements
- Neutrons from Carbon-13: process by which neutrons are freed in the s process
- R-Process: synthesization of elements through neutron capture faster than beta decay
- S-Process: synthesization of elements through neutron capture and beta decay
- Trans-Iron Element: elements with atomic number greater than that of iron
- Metastable: characteristic of an excited state that lasts longer than typical
- Metastable Energy Level:
- Metastable: characteristic of an excited state that lasts longer than typical
- Meteor:
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Meteor Shower:
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Meteorite:
- CAI: calcium/aluminum specs in chondrites
- Carbonaceous Chondrite (C Chondrite): stony meteorites with carbon compounds showing no melting
- Chondrite: stony meteorites showing no melting
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Meter Size Barrier: a barrier to planet formation on the order of a meter diameter
- Meter-Wave Astronomy:
- METH6:
- Methane (CH4): compound of one carbon and 4 hydrogen atoms
- Methane Clathrate:
- Clathrate: crystal lattice with voids that can trap molecules
- method:
- Methyladyne:
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Methylidyne (CH): compound of one carbon and one hydrogen atom
- Metis:
- Metric: mathematical generalization of the concept of distance
- Mexico:
- MGRO:
- Milagro: gamma ray telescope using Cherenkov radiation
- MGS:
- MHD:
- Alfvén Wave: a type of transverse wave along magnetic field lines in plasma
- AstroBEAR: MHD simulation system
- Athena: MHD code
- Current Sheet: narrow sheet within a magnetic field where current flows
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Faraday Rotation: rotation of optical polarization by a medium in a magnetic field
- Flux Rope: rope-shaped structure in magnetic fields associated with coronal mass ejections
- Gas Flow: dynamics of gas, plasma, i.e. compressible fluids
- MagIC: numerical code to for fluid dynamics including dynamos
- Magnetic Arcade: series of arch-like magnetic flux lines on the Sun
- Magnetohydrodynamics (MHD): dynamics of electrically conducting fluids
- Magnetorotational Instability (MRI): instability in the fluid of a disk from MHD effects
- Magnetospheric Truncation Radius: radius at which the disc ram pressure matches the magnetic field pressure
- MHD Drag:
- MHD Dynamo:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- MHS:
- Michelle:
- Michelson Interferometer: device to measure small changes in distance or light speed
- Michelson-Morley Experiment:
- Relativity: physics models accommodating the constancy of the speed of light
- Micro-Bolometer:
- Bolometer: instrument measuring heat produced by radiation
- MicroFUN: observers following up on microlensing events in the galactic bulge
- Microlensing:
- EROS: search for MACHOs
- GMAN: automated survey to identify microlensing transients
- Gravitational Lensing: focusing electromagnetic radiation by gravitational force
- Gravitational Microlensing: gravitational lensing by "small" objects such as individual stars and planets
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- MicroFUN: observers following up on microlensing events in the galactic bulge
- MOA: search for microlensing
- OGLE: survey searching for microlensing transients
- POINTE-AGAPE: survey of M31 for microlensing
- Probing Lensing Anomalies Network (PLANET): automated survey to identify microlensing transients
- Microlensing Event:
- Microlensing Follow-up Network:
- MicroFUN: observers following up on microlensing events in the galactic bulge
- Microlensing Observations In Astrophysics:
- MOA: search for microlensing
- Micrometeoroid:
- Meteoroid: rocky object in solar system, smaller than an asteroid
- Microquasar: stellar-sized black hole with quasar-like activity
- Microvariability and Oscillations of Stars:
- MOST: observatory-satellite to look for stellar oscillations
- Microwave: electromagnetic radiation, frequency 300MHz to 300GHz
- Microwave Amplification by Stimulated Emission of Radiation:
- Maser: electromagnetic radiation amplified by stimulated emission
- Microwave Anisotropy Probe:
- Microwave Radiometer:
- Mid Infrared (MIR): infrared radiation with wavelengths in the 7.5um-25um range
- Mid-Scale Dark Energy Spectroscopic Instrument:
- MIDAS:
- Rosetta: space probe that visited a comet
- Middle Ultraviolet:
- Ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- MIDEX:
- FINESSE: planned space mission for exoplanet spectrography
- NASA: includes space-based astronomy research
- Mie Scattering: scattering of light by large particles
- Mie Theory:
- migration:
- MIKE:
- Mikheyev-Smirnov-Wolfenstein Effect (MSW Effect): neutrino oscillation between three flavors
- Mikulski Archive For Space Telescopes:
- MAST: archive of data from surveys and missions
- Milagro: gamma ray telescope using Cherenkov radiation
- Milky Way: our galaxy
- Milky Way Chemical Evolution: process of the development of metals in the Milky Way
- milli flux unit:
- Jansky (Jy): unit of measurement of spectral flux density
- Millibar:
- Millijansky:
- Jansky (Jy): unit of measurement of spectral flux density
- millimeter:
- Millimeter Array:
- Millimeter Astronomy: observation and analysis at wavelengths on the order of a millimeter
- Millimeter Wave Astronomy:
- Millimeter-wave Intensity Mapping Experiment (mmIME): project to map CO an [CII]
- Millimeter/Submillimeter Astronomy:
- Millisecond Pulsar (MSP): pulsar spinning with a period in the range of milliseconds
- Mills:
- Mimas:
- Moon: Earth's natural satellite
- Saturn: second largest planet in the solar system
- MIMI:
- Cassini: explorer spaceship sent to Saturn
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- MINECO:
- Mini Gas Giant:
- Super-Earth: exoplanet more massive than Earth but substantially less than Neptune
- Mini Neptune:
- Super-Earth: exoplanet more massive than Earth but substantially less than Neptune
- Mini Neptunes:
- Mini-RF:
- Miniature Black Hole:
- Black Hole (BH): region of such high mass that light cannot escape
- Minkowski Diagram:
- Minkowski Metric:
- Metric: mathematical generalization of the concept of distance
- Minor Merger:
- Minor Planet: lesser solar system body without comet characteristics
- 101955 Bennu: near-Earth asteroid that is the target of a planned retrieval mission
- 10199 Chariklo: largest minor planet in the outer solar system
- Planetoid: an asteroid or physically similar body
- Pluto: dwarf planet formerly listed as one of the nine planets
- Minor Planet Center (MPC): organization collecting and organizing minor planet data
- minor planets:
- Mintaka:
- Orion: well-known constellation in the northern hemisphere
- MIPS:
- MIPSGAL:
- MIR:
- Mid Infrared (MIR): infrared radiation with wavelengths in the 7.5um-25um range
- MIRADAS:
- Miranda:
- Moon: Earth's natural satellite
- Uranus: second outer-most solar system planet
- MIRI:
- MIRI MRS:
- MIRIC-BLINC:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MIRO:
- Rosetta: space probe that visited a comet
- mirror:
- Mirror Cell:
- Mirror Support Cell: units in a telescope that support the mirror
- MIRSI:
- IRTF: Mauna Kea 3-meter infrared telescope
- Misaligned Gas:
- MISE:
- mission:
- EPOXI: mission using Deep Impact for further exploration
- K2: second kepler mission working around failed equipment
- Mission Definition Review:
- MDR/SRR: planning step for a NASA mission
- Mission Definition Review/System Requirements Review:
- MDR/SRR: planning step for a NASA mission
- Mission-based Designator:
- missions:
- MDR/SRR: planning step for a NASA mission
- MIT Cosmic X-Ray Experiment:
- OSO 7: 1970s observatory-satellite for viewing the Sun
- MIT General Circulation Model:
- MITgcm: well-known general circulation model
- MIT X-ray Burst Source Catalog (MXB): 1970s catalog of X-ray bursters
- MITgcm: well-known general circulation model
- Mixing Length Model:
- Mixing Length Theory: tractable simplified model of convection
- Mixing Ratio: ratio of two components of a gas
- Mizuguchi-Dragone-Design:
- MJD:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- mJy:
- Jansky (Jy): unit of measurement of spectral flux density
- MK Class:
- MK Luminosity Class:
- MKII:
- Mark II (MKII): 38m radio telescope in England
- Mkn:
- MKO:
- ML Mapmaking:
- MLE:
- MMA:
- mmIME:
- MMIRS:
- Magellan Telescopes: pair of 6.5m optical telescopes in Chile
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMO:
- MMR:
- Orbital Resonance: orbits of multiple bodies that align from periodic gravitational interaction
- MMRTG: power source for space probes
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMT Observatory:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMT Spectrograph:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMT-Pol:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMTCam:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MMTO:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- MOA: search for microlensing
- MOC:
- Mock Catalog: catalog of simulated astronomical bodies
- Mode:
- model:
- models:
- Modified Julian Day:
- Julian Date (JD): time in days since Noon UT November 24 4714 BC Gregorian
- Modified Newtonian Dynamics (MOND): alternative theory of gravity addressing "dark matter"
- MODS:
- Modular Open Source Fitter for Transients:
- Astrocats: software to create and manage an astronomy catalog
- modulation:
- MOIRCS:
- MOJAVE: program to monitor AGN jet radio brightness and polarization
- MOLA:
- Molecular Cloud: interstellar gas cloud including molecules
- CO to H2 Factor (Xco,XCO): assumed ratio between observed CO emission lines and H2 mass
- Filament: linear volume of high molecular gas density within a galaxy
- Nessie: star forming filament found in the Orion star forming region
- Molecular Cloud Filament:
- Filament: linear volume of high molecular gas density within a galaxy
- Molecular Cloud Turbulence: observed turbulence in molecular clouds
- Molecular Deep Field: survey of molecular lines in Hubble Deep Field
- molecular gas:
- CARMA EDGE: CO survey of galaxies
- Cold Gas: gas cool enough to form galaxies and stars
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- EMPIRE Survey: survey of gas in M51a to follow up PAWS
- Filament: linear volume of high molecular gas density within a galaxy
- PAH Emissions: infrared emission from polycyclic aromatic hydrocarbons in gas clouds
- Star Formation Rate (SFR): rate at which material such as gas is turned into stars
- Molecular Gas Depletion Time:
- Galaxy: gravitationally-bound group of stars
- Molecular Gas Fraction:
- Gas Fraction: fraction of a galaxy or cluster consisting of gas
- Molecular Handedness: mirror-image forms of some molecules
- Molecular Hydrogen:
- Molecular Hydrogen Dissociation Front (H2 Dissociation Front): point in a gas cloud where it is hot enough to dissociate hydrogen
- Molecular Orbital:
- Molecular Star Formation Law:
- Molonglo Reference Catalog:
- USS Sources: catalog of sources with steep spectral index
- Molten Core:
- Dynamo: mechanism for generating magnetic fields around astronomical bodies
- Moment of Inertia:
- Precession: periodic change in a body's rotation or orbit
- MOND:
- Monitor of All-sky X-ray Image:
- MAXI: Japanese X-ray camera on the International Space Station
- Monitoring of Jets in Active Galactic Nuclei With VLBA Experiments:
- MOJAVE: program to monitor AGN jet radio brightness and polarization
- Monochromatic Luminosity: luminosity at a specific wavelength
- Monochromator:
- Spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- Monolithic:
- Monolithic Mirror: telescope mirror made of one piece of material
- Monopole:
- Monsoon:
- Monsoon Trough:
- Monte Carlo Method:
- Monte-Carlo:
- Hyperion: Monte-Carlo radiative transfer code
- Moon: Earth's natural satellite
- Morgan Classification: classification of galaxies by stellar spectrum and morphology
- N Galaxy: galaxy with bright nucleus and faint surroundings
- Morgan's Classification:
- Morgan-Keenan Luminosity Class:
- MORIS:
- IRTF: Mauna Kea 3-meter infrared telescope
- Morphological Catalog Of Galaxies:
- Morphological Catalogue Of Galaxies (MCG): 1960s catalog from Palomar plates
- MOSAIC II:
- MOSFIRE:
- MOSFiT:
- Astrocats: software to create and manage an astronomy catalog
- MOST: observatory-satellite to look for stellar oscillations
- CSA: Canadian agency includes astronomical research
- mount:
- Mount Graham:
- Mount Hopkins Observatory:
- Mount Stromlo Observatory:
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- Moving Mesh:
- AREPO: cosmology simulation using moving mesh technique
- Moving-Cluster Method: method of measuring distance to a nearby star cluster
- MOXE:
- MP:
- USS Sources: catalog of sources with steep spectral index
- MPA:
- MeerKAT: new radio telescope in South Africa
- Mpc:
- HEAO-2: 1978 x-ray observatory space mission
- Minor Planet Center (MPC): organization collecting and organizing minor planet data
- Parsec (pc): about 3.26 light-years
- MPG/ESO Telescope:
- MPIA:
- MPIR:
- MPO:
- MR:
- MRC:
- USS Sources: catalog of sources with steep spectral index
- Mre:
- Reynolds Number (Re): measure reflecting a fluid system's propensity to turbulence
- MRI:
- Mrk:
- MRO:
- MRS:
- MS Galaxy:
- MS-DESI:
- MSDESI:
- MSE:
- MSP:
- Msun:
- Sun: star at center of solar system
- MSW Effect:
- Mt. Bigelow:
- Mt. John University Observatory:
- MOA: search for microlensing
- Mt. Lemon:
- Mullard Radio Astronomy Observatory:
- Multi Mirror Telescope:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Multi-Color TES Array Camera:
- Multi-Conjugate AO:
- Adaptive Optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- Multi-messenger Astronomy: astronomy using more than one type of observation
- Multi-mission Radioisotope Thermoelectric Generator:
- MMRTG: power source for space probes
- Multi-Object Spectrograph: device to record the spectrum of multiple targets simultaneously
- Multi-Object Spectrography:
- Multi-Object Spectrometer:
- Multi-site All-sky Camera:
- MASCARA: distributed array of telescopes to search for exoplanets
- Multilevel Relaxation:
- Multiple Star System:
- Multiplexed SQUID TES Array at Ninety GHz:
- MUSTANG: bolometer array on the Green Bank Telescope
- Multiplicity Fraction: fraction of star systems that are multiple-star systems
- Multipole Expansion: series expansion of a function over the surface of a sphere
- Multipole Magnetic Field:
- Munich:
- Muon:
- Muon Neutrino:
- MUPUS:
- Rosetta: space probe that visited a comet
- Murchison Radio-astronomy Observatory:
- Murchison Widefield Array (MWA): low frequency radio telescope
- MUSCLES: HST UV survey of some M-Dwarfs that host exoplanets
- MUSE:
- MUSTANG: bolometer array on the Green Bank Telescope
- MUSTANG-2:
- MUV:
- Ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- MWA:
- MWA-128:
- MWR:
- Mx:
- MXB:
- N:
- N Band:
- Infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- Mid Infrared (MIR): infrared radiation with wavelengths in the 7.5um-25um range
- N Galaxy: galaxy with bright nucleus and faint surroundings
- N-body:
- N-Body Problem: predicting the paths of celestial objects with gravitation interaction
- N-Body Simulation: simulation of many objects gravitationally-bound to each other
- N-PDF:
- N-Point Correlation Function:
- N-Point Function: general term for analyses-techniques of spatial data
- N500:
- Na:
- Sodium (Na): metal, Na, atomic number 11
- NACO:
- NAI:
- NAIC:
- Naked Singularity:
- Namibia:
- Nançay Radio Telescope:
- NANOGrav: effort to detect gravitational waves through pulsar timing
- Nanohertz Gravitational Waves: size of GWs that pulsar-timing observations might catch
- Nanohertz GWs:
- Nanometer:
- Angstrom (Å): unit of length 10-10 meters
- NAOMI:
- Narrow Band Photometry:
- Photometry: studying starlight through bandpass filters
- Narrowband:
- Bandwidth: number of Hertz between minimum and maximum frequencies
- NARVAL:
- NASA: includes space-based astronomy research
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