Term Index (A)
- A:
- A catalog of southern groups and clusters of galaxies:
- 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): star with spectral characteristics of around 8500 K
- A-class star:
- A-type star (A): star with spectral characteristics of around 8500 K
- A-type star (A): star with spectral characteristics of around 8500 K
- Am star: A-type star with metallic lines
- A0 V star:
- A1:
- HEAO-1: 1977 X-ray observatory space mission
- A1689:
- 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
- aw:
- A0:
- axion (A0): proposed light, electrically neutral elementary particle
- AAO:
- AAOmega:
- Anglo-Australian Telescope (AAT): 3.9 m reflector telescope in Australia
- Dark Energy Survey (DES): survey aimed at mapping the universe's expansion
- DEVILS: visible-light spectrographic survey of 56k distant galaxies
- GAMA: galaxy spectroscopy survey to roughly 1 Mpc
- WiggleZ: survey aimed at mapping dark energy
- AAT:
- AAVSO:
- APASS: down to 16 magnitude
- AAVSO Photometric All-sky Survey:
- APASS: down to 16 magnitude
- AB:
- AB magnitude:
- AB system: monochromatic magnitude calibration based upon absolute values
- AB Pictoris:
- AB system: monochromatic magnitude calibration based upon absolute values
- abbreviation:
- HRS: high resolution spectrography
- ABC:
- Abel:
- Abell:
- Abell 1367:
- Abell 1656:
- Abell 262:
- Abell 2667:
- Abell 347:
- Abell 426:
- Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
- aberration: types of flaws in telescope images
- Abetti:
- abiotic oxygen: oxygen from non-life sources
- ablation: erosion of the surface of an object
- ABS:
- ABS telescope:
- absolute astrometry:
- astrometry: precise measurement of the position and movement of stars
- absolute bolometric magnitude:
- absolute hot:
- Planck units: a set of units based on Planck constant and other fundamental constants
- absolute magnitude (M): magnitude as would be seen from 10 parsecs
- absolute photometry:
- photometry: studying starlight through bandpass filters
- Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission:
- ARCADE: balloon-borne centimeter-wavelength surveyor
- absolute zero:
- kelvin (K): temperature scale starting at absolute zero
- absorptance:
- absorption: removal of photons from a beam of EMR
- absorption band:
- absorption coefficient: measure of how much light a substance absorbs
- opacity (κ): a measure of opaqueness of a material
- absorption cross section:
- absorption line: dark line in a spectrum
- absorption line galaxy:
- absorption nebula:
- absorption redshift:
- redshift (z): change to longer wavelengths due to Doppler effects
- absorption spectroscopy:
- absorptivity:
- abstract algebra:
- abundance ratio:
- abundances: relative amounts of each chemical element
- abundance retrieval:
- retrieval: determining measures through observation and modeling
- abundances: relative amounts of each chemical element
- abundances of the chemical elements:
- abundances: relative amounts of each chemical element
- AC:
- ACA:
- Academia Sinica:
- Academia Sinica Institute of Astronomy and Astrophysics (ASIAA,IAA): Taiwanese astrophysics research organization
- ACAM:
- ACBAR: instrument used in CMB search
- ACBAR 2008:
- ACBAR: instrument used in CMB search
- ACBAR08:
- ACBAR: instrument used in CMB search
- Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun:
- THEMIS: set of satellites studying the Earth's magnetic field
- accelerometer:
- accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- accretion disk: disk around an astronomical body of material that is accreting
- accretion induced collapse:
- 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
- ACF:
- Achernar: ninth-brightest star in the sky
- achondrite:
- chondrite: stony meteorites showing no melting
- achromatic transit:
- acidity (pH): measure of the activity of hydrogen ions in a solution
- ACIS: imaging spectrometer on Chandra X-ray telescope
- Ack:
- ACO:
- ACOS:
- acoustic frequency:
- acoustic peak:
- acoustic scale:
- ACP:
- Cassini: explorer spacecraft sent to Saturn
- ACR:
- ACRIM:
- ACRIM2:
- 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 comet:
- comet: Sun-orbiting object with coma and possible tail
- 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
- active phase:
- symbiotic binary (SS): giant star transferring mass to a somewhat distant companion
- ACTPol:
- ACTPol Survey:
- actuator: telescope control motor
- ACV:
- ACYG:
- pulsating star: variable star that varies through energy pulses
- Rigel: brightest star in constellation Orion
- AD Leo:
- AD Leonis (AD Leo): active red dwarf
- ADAF:
- 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
- ADEC: NASA unit to coordinate efforts of data archiving and dissemination
- ADEPT:
- 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
- admittance: effect of atmospheric pressure on gravity
- ADONIS:
- Adrastea:
- Adron-RM:
- ADS:
- AdS/CFT correspondence:
- adsorption: adhesion to a surface
- AdvACT:
- AdvACT Survey:
- Advanced CCD Imaging Spectrometer:
- ACIS: imaging spectrometer on Chandra X-ray telescope
- Advanced Composition Explorer (ACE): satellite collecting solar wind and cosmic rays
- Advanced Dark Energy Physics Telescope:
- Advanced LIGO:
- LIGO: pair of observatories to detect gravitational waves
- Advanced Research and Global Observation Satellite:
- ARGOS: 1999 technology-research satellite
- Advanced Satellite for Cosmology and Astrophysics:
- ASCA: 1990s Japanese space X-ray telescope
- Advanced Telescope for High Energy Astrophysics:
- Advanced Virgo:
- Virgo: ground-based gravitational-wave detector in Italy
- Advanced X-ray Astrophysics Facility:
- advection: transport of something through a fluid's motion
- advection dominated accretion flow (ADAF): accretion without radiating much energy
- 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
- Aeolis Mons:
- aeon:
- aerobraking:
- aerodynamics:
- aerosols: particles suspended in an atmosphere
- AF2:
- AFG:
- AFGL:
- AFGL Four Color Infrared Sky Survey (AFGL): 1970s infrared survey
- AFTA:
- afterglow:
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- AFWA:
- MarsWRF: Mars-oriented general circulation model
- Ag:
- AGAPE:
- AGB:
- AGB star:
- AGC:
- age:
- age of the universe:
- Hubble constant (H0): current rate of expansion of the universe
- Hubble time (tH): approximation of the age 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:
- Agenzia Spaziale Italiana (ASI): includes space-based astronomy research
- AGILE: Italian space gamma-ray observatory
- AGK:
- AGK1:
- AGK2:
- AGK3:
- AGKR:
- AGN:
- AGN bubble:
- AGN feedback:
- AGN jet:
- jet: stream of matter from an astronomical body
- AGN outflow:
- AH03:
- AIA:
- AIC:
- AIC corrected:
- AICc:
- AIM-CO: survey of CO from star forming epoch
- AIPS:
- Air Force Geophysics Laboratory:
- Air Force Weather Agency:
- MarsWRF: Mars-oriented general circulation model
- air mass:
- airmass: measure of Earth-atmosphere attenuation for a telescope observation
- air shower: particles and EMR generated in the atmosphere incoming particle or EMR
- airborne:
- ARCADE: balloon-borne centimeter-wavelength surveyor
- Archeops: balloon-borne 1.8 m submillimeter telescope
- BLAST: balloon-borne 1.8 m submillimeter telescope
- BOOMERanG: 1990s-2000s balloon-borne 1.3-meter millimeter telescope
- COSI: 2000s balloon-based gamma ray telescope
- EBEX: balloon-based CMB polarization survey
- Galileo Observatory: infrared observatory-plane in the early 1970s
- Kuiper Airborne Observatory (KAO): infrared observatory-plane in the 1980s
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- MAXIMA: 1998-1999 balloon-borne 1.3-meter millimeter telescope
- QMAP: mid 1990s balloon-based CMB survey
- SOFIA: aircraft-based infrared observatory
- SPIDER: 2015 airborne observatory to observe CMB polarization
- STARFIRE: planned balloon-borne 2.5 m telescope and spectroscope
- TopHat: 2001 balloon -based CMB survey
- airglow: glow from a planet's atmosphere
- 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
- AIS:
- Aitken Double Star Catalogue (ADS): 1932 catalog with both multiple-star systems and non-orbiting double stars
- Akaike information criterion (AIC): particular formula for comparison of statistical models
- AKARI: Japanese space infrared telescope
- Al:
- albedo: measure of reflectance
- earthshine: reflected and emitted electromagnetic radiation from Earth
- albedo feature:
- albedo: measure of reflectance
- Albion:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Alcock-Paczyński effect (AP effect): type of distortion of the apparent depth of galaxy clusters
- Alcock-Paczyński test:
- ALD:
- ALESS:
- Alessi:
- ALEXIS: 1990s soft X-ray transient monitor
- 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 (NS): 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
- algebra:
- Algol (Beta Per,β Per): multiple star system demonstrating effects of mass transfer
- Algol paradox:
- Algol (Beta Per,β Per): multiple star system demonstrating effects of mass transfer
- Algol variable:
- Algol (Beta Per,β Per): multiple star system demonstrating effects of mass transfer
- variable star: star that varies in magnitude
- Algols:
- Algol (Beta Per,β Per): multiple star system demonstrating effects of mass transfer
- algorithm:
- adaptive refinement tree (ART): algorithm-type for solving n-body problem
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- Alicante:
- ALICE:
- aLIGO:
- LIGO: pair of observatories to detect gravitational waves
- Alinda:
- 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 survey:
- survey field: portion of the celestial sphere where a survey's observations aim
- All-Sky Compiled Catalogue (ASCC,ASCC-2.5): 2001 catalog compiled from modern sources
- 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
- Aller:
- 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
- Proxima b: exoplanet orbiting Proxima Centauri
- Starshot: plan for mission to fly by Alpha Centauri
- Alpha Centauri A:
- Alpha Centauri B:
- Alpha Centauri C:
- alpha CO (αCO): ratio of CO emissions to H2
- Alpha Cygni variable:
- Alpha Cygni variable star:
- Rigel: brightest star in constellation Orion
- alpha disk: well-known model of an accretion disk
- 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 produced by radioactivity
- alpha process: synthesization of elements through alpha capture
- magnesium (Mg): element, Mg, atomic number 12
- neon (Ne): element, Ne, atomic number 10
- alpha ray:
- alpha species:
- Alpha² Canum Venaticorum variable:
- ALS:
- alt-azimuth mount:
- Alt/Az system:
- altazimuth mount: simple two-axis telescope mount
- altazimuth system:
- altazimuth telescope:
- alternative cosmologies: cosmological models other than Big Bang/Lambda-CDM
- altitude:
- altitude-azimuth mount:
- aluminum:
- CAI: calcium/aluminum specs in chondrites
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- globular cluster (GC): spherical group of stars orbiting a galaxy
- silicate: type of compound including silicon and oxygen
- AM:
- AM Herculis star:
- Am star: A-type star with metallic lines
- Am-Fm:
- AMANDA:
- IceCube: neutrino detector at the South Pole
- amateur:
- Astrolux: historically popular amateur telescope
- AMBER:
- AME:
- American Association of Variable Star Observers:
- APASS: down to 16 magnitude
- AMI:
- AMI LA:
- AMI Large Array:
- AMI SA:
- AMI Small Array:
- AMiBA:
- AMICA:
- AMIE:
- SMART-1: Swedish lunary orbiter operational 2004-2008
- amine: type of compound containing nitrogen
- amino acid:
- glycine (Gly,G): smallest of the twenty common amino acids
- amino acids:
- amine: type of compound containing nitrogen
- Lego principle: principle that life is associated with a skew in molecule abundances
- ammonia (NH3): particular compound of nitrogen and hydrogen
- amine: type of compound containing nitrogen
- Amor:
- amorphous galaxy:
- amorphous ice:
- ice: solid state of water
- snow line: distance from protostar cool enough for water to condense
- amorphous ice snow line:
- snow line: distance from protostar cool enough for water to condense
- amorphous-to-crystal ice transition radius:
- snow line: distance from protostar cool enough for water to condense
- amount of substance:
- diffusion: the spreading of particles toward an even distribution
- amp:
- siemens (S): SI unit of electrical conductance
- ampere:
- siemens (S): SI unit of electrical conductance
- Ampere's law:
- amplitude: the height of a wave
- amplitude spectral density:
- 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
- Andrews-Lindsay:
- Andromeda (M31): spiral galaxy in the Local Group
- Milkomeda: future galaxy resulting from merger of Milky Way and Andromeda
- Andromeda Galaxy Amplified Pixels Experiment:
- Andromeda I:
- Andromeda (M31): spiral galaxy in the Local Group
- Andromeda II:
- Andromeda (M31): spiral galaxy in the Local Group
- Andromeda subgroup:
- galaxy subgroup: group of fifty or fewer gravitationally bound Milky-Way-sized galaxies
- Andromeda-Milky_way_collision:
- Milkomeda: future galaxy resulting from merger of Milky Way and Andromeda
- anemic galaxy:
- angle:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- angle of incidence:
- angle of refraction:
- Anglo-Australian Telescope (AAT): 3.9 m reflector telescope in Australia
- angstrom (Å): unit of length 10-10 meters
- angular acoustic scale:
- 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 degree:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- angular diameter distance:
- angular differential imaging:
- angular distance:
- position angle (PA): indication of a direction across the celestial sphere
- angular frequency:
- frequency: number of cycles per unit of time, such as waves per second
- angular hour:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- 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
- point source: celestial object that focuses to a point or single Airy disk
- angular size-redshift relation:
- angular two-point correlation:
- angular velocity:
- angular wavenumber:
- anion:
- ion: non-neutral atom or molecule, with missing or extra electrons
- ANIR:
- anisotropy: directional-dependence such as temperature variation around the CMB
- Anlitak:
- Orion: well-known constellation in the northern hemisphere
- annihilation:
- anomalistic year:
- sidereal: relative to the fixed position of the stars
- anomalous cosmic rays (ACR): cosmic rays with unexpectedly low energies
- anomalous microwave emission (AME): component of microwave background discovered in the 1990s
- anomalous X-ray pulsar (AXP): X-ray pulsars with slow rotation and strong magnetic field
- Anon:
- anorthite:
- CAI: calcium/aluminum specs in chondrites
- Antalova:
- Antarctic Circle:
- circle of latitude: circle around the Earth of points equidistant from a pole or the equator
- Antarctic Muon And Neutrino Detector Array:
- IceCube: neutrino detector at the South Pole
- Antarctica:
- antenna noise temperature:
- antenna pattern: a radio telescope's pattern of directional sensitivity
- antenna temperature: parameter in determining noise introduced by an antenna
- anti-de Sitter space (AdS): type of curved space
- anticenter:
- Anticenter Shell: nebula at edge of Milky Way
- Anticenter Superbubble:
- 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
- antiparticle:
- 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
- quark: type of elementary particle incorporated in protons and neutrons
- Antlia 2:
- Antu Telescope:
- ANU:
- ANU 40-inch Telescope:
- AO:
- AO188:
- AP effect:
- 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
- apastron:
- apsis: closest or furthest point in an eccentric orbit
- APD:
- 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:
- APEX-1:
- APEX-2:
- APEX-2A:
- APEX-3:
- APEX-T2:
- APF:
- 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:
- Apohele:
- Apollo:
- apparent binary:
- apparent elastic thickness:
- elastic thickness (Te): measure of the thickness of a sagging layer of a planet surface
- apparent magnitude (m): magnitude as seen from Earth adjusted for Earth atmosphere
- apparent radiant:
- meteoroid: rocky object in solar system, smaller than an asteroid
- Approximate Bayesian Computation (ABC): shortcut method in Bayesian statistics
- Approximate Places of Double Stars in the Southern Hemisphere:
- appulse: moment of apparent nearest distance of observed bodies
- apsis: closest or furthest point in an eccentric orbit
- APXS:
- aqueous solution:
- acidity (pH): measure of the activity of hydrogen ions in a solution
- Arakelian Catalog (Ark): 1970s list of small/bright galaxies
- arc:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- ARC 3.5m:
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- ARCADE: balloon-borne centimeter-wavelength surveyor
- ARCADE 2:
- ARCADE: balloon-borne centimeter-wavelength surveyor
- Archeops: balloon-borne 1.8 m submillimeter telescope
- Arches:
- Archival Legacy Program:
- archive:
- HEASARC: archive of NASA data on high energy astronomy
- MAST: archive of data from surveys and missions
- arcmin:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- arcminute:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- right ascension (RA): direction coordinate along celestial equator
- Arcminute Cosmology Bolometer Array Receiver:
- ACBAR: instrument used in CMB search
- Arcminute Microkelvin Imager (AMI): pair of microwave arrays
- ARCoRISI:
- arcsec:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- Arctic Circle:
- circle of latitude: circle around the Earth of points equidistant from a pole or the equator
- Arcturus: fourth brightest star in the sky
- Arecibo:
- Arecibo General Catalog (AGC): catalog of galaxies to support ALFALFA surveys
- Arecibo L-band Feed Array:
- Arecibo Observatory (NAIC): large 305 m radio telescope in Puerto Rico
- Arecibo Occultation Survey (AO): 1960s radio survey using occultations by the Moon
- Arecibo Pulsar ALFA Survey:
- PALFA: Arecibo survey for pulsars
- arene:
- hydrocarbon (HC): any compound of just carbon and hydrogen
- AREPO: cosmology simulation using moving mesh technique
- Ares Vallis:
- ARG:
- Argentina:
- ARGO-YBJ Experiment: cosmic-ray/gamma-ray detector in Tibet
- ARGOS: 1999 technology-research satellite
- 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
- argument of perihelion:
- apsis: closest or furthest point in an eccentric orbit
- Argus:
- Ariane:
- Space Launch System (SLS): launch rocket in development, e.g., for future astronomical projects
- Ariel:
- ARIEL: planned space mission for exoplanet spectrography
- moon: a planet's natural satellite, such as Earth's
- Uranus: second outer-most solar system planet
- Ariel 5: 1970s X-ray space telescope
- ARIES:
- MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
- Arizona:
- Arizona Radio Observatory:
- Arjuna:
- Ark:
- ARO 12m Radio Telescope:
- aromatic hydrocarbon:
- Arp:
- 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:
- Array for Microwave Background Anisotropy:
- Array of Low Energy X-ray Imaging Sensors:
- ALEXIS: 1990s soft X-ray transient monitor
- arrays:
- phased array: method of using a set of antennas directionally
- ART:
- ART-P:
- GRANAT: observatory-satellite for detecting gamma rays and X-rays
- ART-S:
- GRANAT: observatory-satellite for detecting gamma rays and X-rays
- ARTEMIS:
- THEMIS: set of satellites studying the Earth's magnetic field
- artificial satellite:
- moon: a planet's natural satellite, such as Earth's
- ARX-XC:
- Spektr-RG (SRG, SXG): Russian-German X-ray observatory launched in 2019
- arXiv.org: website with physics paper preprints
- ASAS:
- ASAS telescope:
- ASAS-SN:
- ASASSN:
- ASASSN telescopes:
- ASCA: 1990s Japanese space X-ray telescope
- ASCC:
- ASCC-2.5:
- ascending node:
- ASD:
- ASI:
- 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:
- Ariel 5: 1970s X-ray space telescope
- Ginga: 1980s Japanese space X-ray telescope
- RXTE: space mission to time X-ray variations
- ASP:
- ASPECS: millimeter survey of HUDF
- ASPERA:
- Assembly and Manufacturing:
- OSAM-1: prototype space robot for servicing satellites
- Association of Universities for Research in Astronomy (AURA): group of universities operating a number of observatories
- AST:
- NSF AST: US government astronomical research funding division
- ASTE:
- ASTE Band8:
- asterism: easily recognizable star pattern
- asteroid: minor planet without comet characteristics
- 101955 Bennu: near-Earth asteroid that is the target of a sample-return mission
- Ceres: dwarf planet and largest asteroid
- asteroid belt: ring 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:
- asteroseismology: study of stars through analysis of their pulsation
- normal mode: sinusoidal oscillation, such as in seismology
- asterosphere:
- astigmatism: focusing differently according to direction across the focal plane
- Astro:
- Astro G:
- HALCA: Japanese space radio telescope operating 1997-2005
- 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
- astrograph: telescope designed for astrometry and other precise position measurements
- Astrographic Catalog (AC): historical star catalog of the whole sky to magnitude 11
- Astrographic Catalog / Tycho:
- Hipparcos: ESA astrometry space observatory circa 1990
- Astrographic Chart:
- 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
- ASTRON: Netherlands radio astronomy research organization
- Astronet: European astronomy consortium
- astronomer:
- Hipparchus: Greek astronomer who developed concept of magnitude
- astronomical aberration:
- astronomical body:
- astronomical catalog: lists of observed astronomical bodies and their characteristics
- Astronomical Image Processing System (AIPS): software for processing radio astronomy data
- astronomical object: planet, star, galaxy, etc.
- astronomical quantities: some astronomy amounts/numbers
- astronomical scintillation:
- twinkling: blinking, apparent movement and color changes of observed stars
- Astronomical Society of the Pacific:
- astronomical survey: project to collect uniform astronomical data across the sky
- astronomical symbol: traditional symbols specific to astronomy, for Sun, Earth, etc.
- astronomical unit (AU): about 93 million miles
- Astronomische Gesellschaft:
- Astronomische Gesellschaft Katalog (AGK): 19th/20th century astrometric catalog
- astronomy:
- appulse: moment of apparent nearest distance of observed bodies
- asterism: easily recognizable star pattern
- astrometry: precise measurement of the position and movement of stars
- astronomical object: planet, star, galaxy, etc.
- astronomical unit (AU): about 93 million miles
- barycenter: center of mass of two orbiting bodies
- Bayer designation: star designation system dating from 1600s
- blind survey: survey conducted independently of prior information
- cadence: period between observations
- celestial event: generally something happening visible in the sky
- celestial sphere: the sky in considered as a sphere surrounding the observer
- circle of latitude: circle around the Earth of points equidistant from a pole or the equator
- confusion limit: limit on telescope imaging due to too many sources in the same region
- constellation: division of the celestial sphere
- counterpart: image found at same coordinates using different EMR
- dark sky: sky with limited light pollution
- data cube: "table" of numerical data covering three dimensions
- data release (DR): publication or distribution of a set of data from a survey
- double star designation: Systems and format of double star designators
- Eddington bias: selection bias from mistaking something common for something rare
- ephemeris: information on the position of a celestial body in the sky over time
- epoch B1950.0: midnight 1/1/1950 GMT as used as a time reference
- epoch J2000.0: noon 1/1/2000 GMT as used as a time reference
- extended source: term for astronomical object producing EMR that can be focused
- extragalactic astronomy: astronomy of other galaxies, galaxy clusters, AGNs, quasars, etc.
- field: adjective meaning "in this field of view but unrelated"
- Flamsteed designation: star designation system dating from 1700s
- flux density: measure of the strength of a radio signal
- foe: unit of energy on the order of a supernova's output
- galactic anticenter: direction opposite the galactic center
- galactic astronomy: astronomy confined to the Milky Way
- galactic north: direction perpendicular to the galactic plane that's north of Earth's equator
- great debate: historical debate regarding the nature of galaxies
- guest observer (GO): non-affiliated researcher welcomed to use an observatory
- guest star: translation of ancient Chinese term for a visible transient
- heliocentric system: model of the universe with the planets orbiting the Sun
- interferometry: analysis of superimposed EMR waves
- International Astronomical Union (IAU,UAI): association of professional astronomers
- interstellar astrophysics: astronomy of the ISM including dust and clouds
- J designator: designator using equatorial coordinates at year 2000
- J2000.0 equinox: equinox as of the J2000.0 epoch used as a positional reference
- jansky (Jy): unit of measurement of spectral flux density
- legacy survey: phrase sometimes used in survey names
- light curve: changing intensity of light from a transient
- light pollution: light from cities that interferes with astronomical observation
- light-year (ly): distance that light travels in a year
- limb: the edge of an astronomical object as viewed
- limb darkening: the darkening of edge of a body such as the Sun
- low frequency radio astronomy: astronomy using the lower end of the radio spectrum
- Malmquist bias: selection bias from detecting only the brighter objects
- mean anomaly: angle describing an object's position within an elliptical orbit
- millimeter astronomy: observation and analysis at wavelengths on the order of a millimeter
- multi-messenger astronomy: astronomy using more than one type of observation
- NSF AST: US government astronomical research funding division
- obliquity: angle between an object's rotational and orbital axes
- observational astronomy: term covering observation
- observatory: facility for astronomical observation
- occultation: one celestial body hiding another from an observer
- opposition: positioning of two astronomical objects 180 degrees apart in the sky
- orrery: mechanical device to simulate the solar system
- panchromatic: involving all colors, i.e., all wavelengths
- parsec (pc): about 3.26 light-years
- phase angle: view angle of reflected light implied by the phase of the Moon
- phone number: colloquial expression for coordinates
- photometry: studying starlight through bandpass filters
- plane of the sky (POS): plane tangent to the celestial sphere
- planetary science: study of planet characteristics
- polarimetry: measurement of polarization of EMR
- primary: central body of a system such as the Sun in the solar system
- projected separation: lower limit on distance between two objects in same part of the sky
- provisional designation: way to designate newly discovered solar system objects
- radio astronomy: astronomy observation and analysis of radio EMR
- radiometer equation: shows how long to observe a radio source
- RMS astronomy: collective term for radio, millimeter, and submillimeter
- Roemer delay: timing differences in observed phenomenon due to Earth's position
- secondary eclipse: eclipse of a body that also transits
- secular: occurring slowly over a long period of time
- sidereal: relative to the fixed position of the stars
- SIMBAD: online database of astronomical objects
- solar mass (MSun,Msun): mass unit representing the mass of the Sun
- solar neutrino unit (SNU): unit for the detection rate of neutrino detectors
- spectral line designation: labels used to identify spectral lines
- spectrography: charting the strengths of different electromagnetic wavelengths
- spectrometry: measuring the strengths of different electromagnetic wavelengths
- spectroscopy: measurement of light with various electromagnetic wavelengths
- star cloud: lighter region of the night sky consisting of a high density of stars
- star count: surveys of stars counting them according to some criteria
- stellar astronomy: astronomy of the birth, structure, variety, evolution, and fate of stars
- Stelle Doppie: online database of double stars
- stray light: unintended light reaching a telescope's sensors
- submillimeter astronomy: astronomy observation and analysis of borderline infrared EMR
- submillimeter galaxy designator: designation system of submillimeter galaxies
- supernova designator: typical designation of supernovae
- supernova survey: survey to identify and/or study supernovae
- survey-based designator: astronomical object designators based on name of survey
- synodic period: period until a planet returns to the same position relative to the Sun
- synoptic: general, covering everything
- synthetic photometry: deriving photometry-style data from spectroscopy
- telescope: instrument to observe at a distance
- terminator: line between regions of day and night
- Titius-Bode law: relationship between the distances between solar system planets
- tracer: chemical whose presence indicates the presence of another chemical
- transient: observed change in the sky
- transient astronomy: study of short-term astronomical phenomena
- transit: a celestial body passing between another and an observer
- ultraviolet astronomy: astronomy observation and analysis of UV
- variable star designation: Bayer system variant for variable stars
- virtual observatory (VO): online database of astronomical data
- volume weighting: method of accommodating the Malmquist bias
- astrophysical jet:
- jet: stream of matter from an astronomical body
- astrophysics:
- astronomical quantities: some astronomy amounts/numbers
- Astrophysics Data System (ADS): website with astrophysics bibliography and paper archive
- black hole binary (BHB,BBH): two black holes co-orbiting
- Blandford-Payne mechanism (BP process): means of extracting BH rotational energy by magnetized accretion disk
- Blandford-Znajek mechanism (BZ process): means of extracting BH rotational energy by magnetized accretion disk
- celestial mechanics: study of forces and motion of celestial objects
- Chandrasekhar limit: maximum mass of a white dwarf
- cold dark matter (CDM): one of three types of "dark matter" theory
- color-color diagram (CCD): means of comparing characteristics of stars
- color-magnitude diagram (CMD,CM): graph plotting stars' color to luminosity
- color-period diagram: means of comparing periods of stars at various wavelengths
- core collapse: results when the center of something loses its pressure
- cosmic rays (CR): very-high-energy particles from beyond the solar system
- critical density (ρc): density of the universe which leaves it flat
- erg: CGS unit of energy
- free-fall time: time it would take a body to collapse if unopposed
- fuzzy dark matter (FDM): concept of extremely light dark matter particles
- galaxy age determination: methods of estimating a galaxy's age
- galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- H-R diagram (HRD): diagram relating effective temperature to luminosity
- halo abundance matching (HAM): method of comparing observed galaxies with cosmology models
- Hayashi limit: limit on the temperature of a star dependent upon its mass and luminosity
- heliopause: boundary between solar wind and the interstellar medium
- Hess diagram: diagram relating effective temperature to luminosity
- high-energy astrophysics (HEA): astronomy and physics of X-rays and gamma rays
- Hill radius: radius of gravitational influence of a body
- instability strip: region of H-R diagram where stars are unstable
- Jeans length: critical radius below which gravity will collapse a cloud
- Kelvin-Helmholtz timescale (KH timescale,KH time,τKH): time that would radiate away a body's heat energy given its luminosity
- Kennicutt-Schmidt law: relation between gas density and star formation rate
- Kepler radius: radius at which a particular velocity would orbit
- Kepler's laws: laws of the kinematics of orbits
- Lagrangian point: points around two orbiting bodies where small objects sit
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- Lane-Emden equation: form of equation of state for gas ball in hydrostatic equilibrium
- local standard of rest (LSR): velocity with respect to our region of the Milky Way
- local thermodynamic equilibrium (LTE): state where temperature variation is too small to matter
- mass density: density of a volume of space
- P-Pdot diagram: diagram comparing the rotation and the slowing of pulsars
- peculiar velocity: velocity with respect to local rest
- plasma astrophysics: includes cosmology, IGM, ISM, HI regions
- Poynting-Robertson effect: force slowing dust grains orbiting a star
- radial velocity (RV): component of velocity toward or away from observer
- redshift-angular size relation: how observed size depends on redshift
- redshift-magnitude relation: how apparent magnitude depends on redshift
- relativistic astrophysics: physics applicable to cosmology and strong field gravity
- repulsive dark matter (RDM): concept of dark matter that resists extreme dark-matter density
- retrieval: determining measures through observation and modeling
- Schönberg-Chandrasekhar limit: maximum stellar isothermal helium core mass
- signatures of formation: qualities of a body that suggest how it was formed
- solar physics: study of the physics of the Sun
- stellar age determination: methods of estimating a star's age
- stellar distance determination: methods by which the distance to a star is determined
- stellar luminosity determination: methods by which the luminosity of a star is determined
- stellar mass determination: methods by which the mass of a star is determined
- stellar parameter determination: methods by which the parameters of stars are determined
- stellar radius determination: methods by which the radius of a star is determined
- stellar rotation: rotation of a star around an axis through the middle
- stellar temperature determination: methods by which the temperature of a star is determined
- systemic velocity: average velocity of grouped objects, such as a galaxy
- tidal locking: locked rotation of an orbiting body
- Tolman-Oppenheimer-Volkoff limit (TOV,LOV): maximum mass of a neutron star
- turn-off point (TO): point in H-R diagram of a cluster where stars turn red
- Yarkovsky effect: force on spinning, orbiting objects from asymmetric radiation
- Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP): rotational effect on asymmetric asteroids
- Astrophysics Data Centers Executive Council:
- ADEC: NASA unit to coordinate efforts of data archiving and dissemination
- Astrophysics Data Service:
- Astrophysics Data System (ADS): website with astrophysics bibliography and paper archive
- Astrophysics Focused Telescope Assets:
- asymmetrical galaxy:
- galactic tide: effect of one galaxy's gravity, such as on another galaxy
- asymptotic giant branch (AGB): a second stage of helium burning in some stars
- AT:
- ATA:
- ATA-350:
- ATA-42:
- Atacama B-Mode Search (ABS): 2012-2014 survey of the CMB
- Atacama Compact Array:
- Atacama Cosmology Telescope (ACT): 6 meter microwave survey telescope in Chile
- D56: a target survey field of ACT telescope
- 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:
- Aten:
- Athena: MHD code
- Atira:
- 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
- ATLAS-1:
- FAUST: 1990s ultraviolet space telescope used on two shuttle missions
- ATLAS3D:
- ATLAS3D:
- atm: unit of pressure
- atmosphere: gas surrounding astronomical object
- atmosphere formation: capture and modification of a planet's gases
- atmospheric escape: escape of gas particles from a planet's atmosphere
- atmospheric extinction:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- atmospheric formation:
- 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 within which the atmosphere passes EMR
- ionosphere: layers of Earth atmosphere with significant ions
- ATNF:
- ATNF Pulsar Catalogue: online catalog of pulsars
- 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 number:
- element: class of atom based on its number of protons
- atomic mass unit:
- atomic number (Z): number of protons in an atomic nucleus
- element: class of atom based on its number of protons
- fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- isotope: subclass of an element with a specific number of nucleons
- neutron capture: combination of an atomic nucleus and a neutron
- radioactive decay: changes in atomic nuclei that happen over time
- atomic orbital:
- atomic weight:
- element: class of atom based on its number of protons
- atoms:
- attenuation coefficient:
- AU:
- AU Mic:
- AU Microscopii (AU Mic): nearby star with disk and planets
- Auger de-excitation:
- Auger effect: mechanism by which ions emit an electron after receiving one
- Auger effect: mechanism by which ions emit an electron after receiving one
- AURA:
- aurora: light produced by atmosphere and solar wind
- aurora australis:
- aurora: light produced by atmosphere and solar wind
- aurora borealis:
- aurora: light produced by atmosphere and solar wind
- Australia:
- Australia Telescope Compact Array (ATCA): radio telescope in eastern Australia
- Australia Telescope Large Area Survey (ATLAS): radio survey of two survey fields
- Australia Telescope National Facility:
- Australian Astronomical Observatory:
- Australian Long Baseline Array:
- Australian National University:
- Australian Square Kilometre Array Pathfinder (ASKAP): radio telescope array of 36 12-meter dishes
- autoconversion rate: rate at which water changes from cloud droplets to new raindrops
- automated:
- Automated Planet Finder (APF): robotic telescope to find exoplanets using RV method
- Automatic Plate Measuring Machine:
- Autonomous Space Transport Robotic Operations (ASTRO): experiment re robotic satellite servicing/refueling in space
- autumnal equinox:
- equinox: times when tilt of Earth is neither toward or away from the Sun
- avalanche photodiode:
- Avogadro constant:
- Avogadro's number (NA): roughly number of hydrogen atoms in a gram
- ideal gas law: relates pressure, temperature, and volume
- mole (mol): unit roughly the count of hydrogen atoms in a gram
- AXAF:
- axial precession:
- axial tilt:
- obliquity: angle between an object's rotational and orbital axes
- axiom:
- axion (A0): proposed light, electrically neutral elementary particle
- dark matter: matter suggested by gravity in galaxies and galaxy clusters
- exotic star: term for theoretical stars not made of atoms/ions
- axisymmetric: identical in any direction from an axis
- axisymmetric galaxy:
- galaxy: gravitationally-bound group of stars
- AXP:
- az/el system:
- azane:
- ammonia (NH3): particular compound of nitrogen and hydrogen
- azimuth:
- azimuth-elevation mount:
- azimuthal quantum number:
- AzTEC:
- AzTEC J100020.54+023509.3:
- AzTEC-3: very distant starburst galaxy
- AzTEC-3: very distant starburst galaxy
- AzV:
Index