Term Index (A)
- A:
- A-type star (A): type of star with about 2 times the mass of the Sun
- APM Galaxy Survey (APMUKS): 1990s survey of galaxies in southern sky
- scale factor (a): relative size of the universe as a function of time
- 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
- Am star: A-type star with metallic lines
- 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
- aw:
- A0:
- axion (A0): proposed light, electrically neutral elementary particle
- AAO:
- AAOmega:
- Anglo-Australian Telescope (AAT): 3.9m reflector telescope in Australia
- 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 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
- 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
- Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission:
- ARCADE: balloon-borne centimeter-wavelength surveyor
- 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 nebula:
- absorption redshift:
- redshift (z): change to longer wavelengths due to Doppler affects
- absorption spectroscopy:
- abstract algebra:
- 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:
- AGILE: Italian space gamma-ray observatory
- Astrographic Catalog (AC): historical star catalog of the whole sky to magnitude 11
- ACA:
- Academia Sinica:
- Academia Sinica Institute of Astronomy and Astrophysics (ASIAA,IAA): Taiwanese astrophysics research organization
- ACAM:
- 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 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 (pH): measure of the activity of hydrogen ions in a solution
- ACIS: imaging spectrometer on Chandra X-ray telescope
- ACO:
- acoustic frequency:
- acoustic peak:
- ACP:
- Cassini: explorer spaceship sent to Saturn
- 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
- active phase:
- ACTPol:
- ACTPol Survey:
- actuator: telescope control motor
- ACV:
- ACYG:
- 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:
- 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 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:
- WFIRST: proposed space observatory
- Advanced LIGO:
- LIGO: pair of observatories to detect gravitational waves
- 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:
- aerodynamics:
- aerosols: particles suspended in an atmosphere
- AF2:
- AFTA:
- WFIRST: proposed space observatory
- AFWA:
- MarsWRF: Mars-oriented general circulation model
- AGAPE:
- AGB:
- AGB star:
- AGC:
- 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:
- Agenzia Spaziale Italiana (ASI): includes space-based astronomy research
- AGILE: Italian space gamma-ray observatory
- AGK:
- AGK1:
- AGK2:
- AGK3:
- AGN:
- AGN bubble:
- AGN feedback:
- AGN outflow:
- AIA:
- AIM-CO: survey of CO from star forming epoch
- AIPS:
- Air Force Weather Agency:
- MarsWRF: Mars-oriented general circulation model
- air mass:
- airmass: measure of Earth-atmosphere attenuation for a telescope observation
- air shower:
- airborne:
- ARCADE: balloon-borne centimeter-wavelength surveyor
- BLAST: balloon-borne 1.8m submillimeter telescope
- Galileo Observatory: infrared observatory-plane in the early 1970s
- Kuiper Airborne Observatory (KAO): infrared observatory-plane in the 1980s
- SOFIA: aircraft-based infrared observatory
- STARFIRE: planned balloon-borne 2.5m telescope and spectroscope
- 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 emitted electromagnetic radiation from Earth
- albedo feature:
- albedo: measure of reflectance
- Alcock-Paczyński effect: distortion of the apparent size of galaxy clusters
- Alcock-Paczyński test:
- ALESS:
- 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: 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 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 survey:
- 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 Centauri A:
- Alpha Centauri B:
- Alpha Centauri C:
- alpha CO (αCO): ratio of CO emissions to H2
- 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 stemming from radioactivity
- alpha process: synthesization of elements through alpha capture
- alpha ray:
- alpha species:
- Alpha² Canum Venaticorum variable:
- alt-azimuth mount:
- Alt/Az system:
- altazimuth mount: simple two-axis telescope mount
- altazimuth system:
- altazimuth telescope:
- 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
- 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
- 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
- amine: type of compound containing nitrogen
- 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 Galaxy Amplified Pixels Experiment:
- 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
- DEVILS: visible-light spectrographic survey of 56k distant galaxies
- GALAH: survey of Milky Way with an emphasis on old structures
- 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 hour:
- arcsecond (arcsec,sec): 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
- angular size-redshift relation:
- angular two-point correlation:
- angular velocity:
- ANIR:
- anisotropy: directional dependence such as temperature variation in the CMB
- Anlitak:
- Orion: well-known constellation in the northern hemisphere
- annihilation:
- 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
- Antarctic Muon And Neutrino Detector Array:
- IceCube: neutrino detector at the South Pole
- antenna noise temperature:
- antenna pattern: a radio telescope's pattern of directional sensitivity
- antenna temperature: parameter in determining noise introduced by an antenna
- 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
- 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:
- 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:
- apparent binary:
- 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 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 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
- archive:
- HEASARC: archive of NASA data on high energy astronomy
- MAST: archive of data from surveys and missions
- arcmin:
- arcsecond (arcsec,sec): a 3600th of an angular degree
- arcminute:
- arcsecond (arcsec,sec): a 3600th of an angular degree
- ARCoRISI:
- arcsec:
- arcsecond (arcsec,sec): a 3600th of an angular degree
- arcsecond (arcsec,sec): a 3600th of an angular degree
- 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 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:
- 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
- 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:
- 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
- ARTEMIS:
- THEMIS: set of satellites studying the Earth's magnetic field
- artificial satellite:
- moon: a planet's natural satellite, such as Earth's
- arXiv.org: website with physics paper preprints
- ASAS:
- ASAS-SN:
- ASASSN:
- ascending node:
- 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:
- 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
- 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 planned sample-return mission
- 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:
- asteroid belt: ring 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: space mission aiming 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:
- 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 (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 catalog: lists of observed astronomical bodies and their characteristics
- Astronomical Image Processing System (AIPS): software for processing radio astronomy data
- astronomical quantities: some astronomy amounts/numbers
- astronomical survey: project to collect uniform astronomical data across the sky
- astronomical unit (AU): about 93 million miles
- Astronomische Gesellschaft:
- Astronomische Gesellschaft Katalog (AGK): 19th/20th century astrometric catalog
- astronomy:
- astrophysics:
- 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:
- WFIRST: proposed space observatory
- asymptotic giant branch (AGB): a second stage of helium burning in some stars
- AT:
- 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
- CCAT-prime (CCAT-p): planned 6 meter submillimeter telescope in Chile
- 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 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 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
- ionosphere: layers of Earth atmosphere with significant ions
- 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:
- 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
- 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
- AURA:
- 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
- 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
- Automated Planet Finder (APF): robotic telescope to find exoplanets using RV method
- HATNet: distributed array of telescopes to search for transients
- KELT: pair of telescopes searching for transients
- MASCARA: distributed array of telescopes to search for exoplanets
- MEarth Project (MEarth): automated observatories monitoring nearby red dwarfs for transits
- NGTS: survey of transits from Chile
- Palomar 48 Inch Telescope (P48): 48 inch Schmidt 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
- RoboNet: global network of robotic telescopes to follow up on GRBs
- 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
- 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
- Avogadro constant:
- AXAF:
- 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
- AXP:
- az/el system:
- azane:
- ammonia (NH3): compound of nitrogen and hydrogen
- azimuth:
- azimuth-elevation mount:
- azimuthal quantum number:
- AzTEC:
- AzTEC-3: very distant starburst galaxy
- AzV:
index