Term Index (A)

 A0  A1  A2  A3  A4  A6  A8  AA  AB  AC  AD  AE  AF  AG  AH  AI  AJ  AK  AL  AM  AN  AO  AP  AQ  AR  AS  AT  AU  AV  AW  AX  AZ

• A (A-type star): star with spectral characteristics of around 8500 K
• A (mass number): number of nucleons in an atomic nucleus
• A: see APM Galaxy Survey
• A: see Abell Catalog
• A: see Ariel 5
• A: see Reference Catalogue of Bright Galaxies
• A: see double star designation
• A: see rare designator prefixes
  • siemens: SI unit of electrical conductance
• a (scale factor): relative size of the universe as a function of time
• A Bag of Stellar Tracks and Isochrones (BaSTI): database relating isochrones to stellar parameters
• A Broadband Imaging X-ray All-sky Survey: failed 1999 space mission
• A catalog of southern groups and clusters of galaxies (Duus-Newell catalog): list of southern galaxies/clusters assembled in 1970s
• A Multiwavelength Study of ELAN Environments (AMUSE²): survey of ELANs
• 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&A (Astronomy & Astrophysics): European scientific journal
• A&G Unit: see William Herschel Telescope
• AΩ (etendue): measure of how wide and deep a telescope observes
• A+E galaxy: see emission line galaxy
• A-class: see A-type star
• A-class star (A-type star): star with spectral characteristics of around 8500 K
• A-LIST: catalog of templates of H-band spectra for SPS
• A-type star: star with spectral characteristics of around 8500 K
  • Am star: A-type star with metallic lines
  • Ap star: peculiar type of A star
• A/2017 U1 (Oumuamua): small body that passed through the solar system in 2017
• A0 V star
• UBV photometric system: commonly-cited photometric system for describing stars' colors
• A1: see HEAO-1
• A1689 (Abell 1689): very massive galaxy cluster
• A1689: see rare designator prefixes
• A2: see HEAO-1
• A2744: see rare designator prefixes
• A3: see HEAO-1
• A4: see HEAO-1
• A66 85: see Abell 85
• A85 (Abell 85): galaxy cluster with central giant elliptical galaxy
• a_w (water activity): measure of partial vapor pressure of water
• A⁰ (axion): proposed light, electrically neutral elementary particle
• AAA (Amateur Astronomers Association of New York): American organization
• AAO
• UK Schmidt Telescope: 1.2 meter telescope in Australia with wide field-of-view
• AAO/UKST Hα Survey: see SuperCOSMOS Sky Survey
• AAOmega: see Anglo-Australian Telescope
  • Dark Energy Survey: 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
  • Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
  • WiggleZ: survey aimed at mapping dark energy
• AAP: see Llano de Chajnantor Observatory
• AAS (American Astronomical Society): American organization
• AAS Job Register: directory of astrophysics jobs
• AAT (Anglo-Australian Telescope): 3.9-m reflector telescope in Australia
  • 2dF-SDSS LRG and QSO survey: spectroscopic survey of distant galaxies
  • Dark Energy Survey: survey aimed at mapping the universe's expansion
  • DEVILS: visible-light spectrographic survey of 56k distant galaxies
  • GALAH: survey of Milky Way with an emphasis on old structures
  • GAMA: galaxy spectroscopy survey to roughly 1 Mpc
  • Hawaii K-band Galaxy Survey: near-infrared survey of a selection of fields
  • RESOLVE­: galaxy and gas survey limited to 65-100 Mpc
  • Siding Spring Observatory: observatory in New South Wales, Australia
  • Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
  • Uppsala-ESO Survey of Asteroids and Comets: 1990s comet and asteroid survey
• AAVSO (American Association of Variable Star Observers): organization of amateur observers of variable stars
  • APASS: down to 16 magnitude
• AAVSO Photometric All-sky Survey (APASS): down to 16 magnitude
• AB: see rare designator prefixes
• AB Aur (AB Aurigae): YSO with disk apparently forming planets
• AB Aurigae: YSO with disk apparently forming planets
• AB Aurigae b: see AB Aurigae
• AB magnitude (AB system): monochromatic magnitude calibration based upon absolute values
• AB magnitude system (AB system): monochromatic magnitude calibration based upon absolute values
• AB Pic (AB Pictoris): K-type star with possible planet
• AB Pictoris: K-type star with possible planet
  • Tucana Horologium association: nearby stellar association
• AB Pictoris b: see AB Pictoris
• AB system: monochromatic magnitude calibration based upon absolute values
• ABBA (ADC Backend For Bolometer Array): APEX instrument
• abbreviation
• AMOS: Advanced Maui Optical and Space Surveillance Technologies Conference
• API: application programming interface
• BEL: broad emission line
• BJD: barycentric Julian day
• BOAT: brightest of all time
• CHNOPS: six common elements in biological molecules
• CHON: four common elements in biological molecules
• CST: variable star type meaning it is currently thought non-variable
• DEIA: abbreviation used for US government efforts
• DRDF: "Director's Research and Development Fund"
• DRS: data reduction system
• EIE: Italian engineering company that produces astronomical equipment
• EPO: "education and public outreach"
• FTL: "faster than light"
• GCRT: galactic center radio transient
• global navigation satellite system: type of space-based service that can impede radio astronomy
• high time-resolution astrophysics: second-by-second observation of/for transients
• HRS: high resolution spectrography
• Intracluster: region between objects of a cluster such as between stars in a star cluster
• laser com: laser communications
• line of sight: line between observer and observed object
• LN₂: "liquid nitrogen"
• LOSVD: line-of-sight velocity distribution
• LPR: for "light pollution reduction"
• maggie: AB magnitude
• MSSSO: Mount Stromlo and Siding Spring Observatories
• nanomaggie: a billionth of an AB magnitude
• NELM: naked eye limiting magnitude
• non-thermal: regarding radiation other than black-body
• PDR: review checking initial design with requirements
• RIX: enquiry/answer about some issue regarding a project review
• Stripe 82: SDSS field in southern hemisphere
• TAC: telescope allocation committee
• TAC: time allocation committee (for telescopes)
• telescope nut: avid amateur telescope maker self-description
• telescope operator: professional technical position at a research telescope site
• thermal infrared: infrared emission due to black body radiation
• TLM: magnitude of the dimmest astronomical object you can see
• TOA: time of arrival
• ToO: target of opportunity
• total infrared: typically meaning a wide wavelength range covering NIR to FIR
• total infrared luminosity: luminosity over a wide IR range
• UF: "ultra faint"
• unidentified flying object: reported but unexplained observation
• Venus-Earth-Earth Gravity Assist: interplanetary method of Galileo spacecraft
• very low luminosity object: term sometimes used for protostars with luminosity less than 0.1 solar
• very low mass: abbreviation
• very small grains: dust grains of just a few molecules
• white paper: paper giving a general explanation of an issue or proposal
• WIT: "what is it" for an unexplainable object
• WIYN: Wisconsin-Indiana-Yale-NOAO
• wrt: "with respect to"
• zenith hourly rate: a meteor shower's maximum meteors/per/hour rate
• ABC (Approximate Bayesian Computation): shortcut-method in Bayesian statistics
• Abel 3627
• ESO 137-001: barred spiral galaxy in the Abell 3627 cluster
• Abell (Abell Catalog): galaxy cluster catalog assembled over 1950s-1980s
• Abell: see Palomar Globular Clusters
• Abell: see rare designator prefixes
• Abell 1367
• Coma Supercluster: nearby supercluster
• Abell 1656
• Coma Supercluster: nearby supercluster
• Abell 1689: very massive galaxy cluster
  • galaxy cluster: large group of galaxies gravitationally-bound to the group
• Abell 262
• Perseus-Pisces Supercluster: nearby supercluster
• Abell 2667
• Comet Galaxy: unique spiral galaxy in cluster Abell 2667
• Abell 347
• Perseus-Pisces Supercluster: nearby supercluster
• Abell 426 (Perseus Cluster): large galaxy cluster in the Perseus-Pisces Supercluster
  • Perseus-Pisces Supercluster: nearby supercluster
• Abell 85: galaxy cluster with central giant elliptical galaxy
  • galaxy cluster: large group of galaxies gravitationally-bound to the group
• Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
  • ESO Nearby Abell Cluster Survey: 1990s spectroscopy and photometry survey of galaxy clusters
• aberration: types of flaws in telescope images
  • astigmatism: focusing differently according to direction across the focal plane
  • barrel distortion: distortion such that a square shows with convex edges
  • chromatic aberration: focusing different wavelengths differently
  • distortion: aberration where the image is in focus but misshaped
  • field curvature: focusing to a curved surface rather than a plane
  • focal plane tilt: focal plane not perpendicular to the optical axis
  • pincushion distortion: distortion such that a square shows with concave edges
  • spherical aberration: mis-focusing by spherically-curved mirrors and lenses
• Abetti: see rare designator prefixes
• ABGC: see Abell Catalog
• abiotic: produced by something other than life
• abiotic oxygen: oxygen from non-life sources
• ablation: erosion of the surface of an object
• ABRIXAS (A Broadband Imaging X-ray All-sky Survey): failed 1999 space mission
• ABS (Atacama B-Mode Search): 2012-2014 survey of the CMB
• ABS telescope: see Atacama B-Mode Search
• absolute abundance: see metallicity
• absolute astrometry: see astrometry
• absolute bolometric magnitude (bolometric magnitude): absolute magnitude of all wavelengths
  • luminosity: measure of brightness
• absolute hot: see Planck units
• absolute magnitude: magnitude as would be seen from 10 parsecs
• absolute metallicity: see metallicity
• absolute photometry: see photometry
• Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE): balloon-borne centimeter-wavelength surveyor
• absolute zero: see kelvin
• absorptance: see emissivity
  • Kirchhoff's law of thermal radiation: for an object in thermodynamic equilibrium, emissivity equals absorptance
• absorption: removal of photons from a beam of EMR
  • 2175 angstrom feature: prominent absorption feature in ISM
  • absorption coefficient: measure of how much light a substance absorbs
  • absorption line: dark line within a spectrum
  • atmospheric window: frequency bands within which the atmosphere passes EMR
  • Balmer jump: abrupt change in stellar spectrum at the Balmer series wavelength limit
  • cavity-enhanced absorption spectroscopy: passing a beam through a gas multiple times to amplify absorption lines
  • continuous absorption: the absorption of a whole section of a spectrum
  • dark nebula: cloud that obscures stars behind it
  • diffuse interstellar bands: type of absorption bands seen in astronomical objects
  • Einstein coefficients: a substance's probabilities of emission and absorption
  • extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
  • Gunn-Peterson trough: spectral feature in EMR from redshift 6+
  • helium 1083 nm line: line useful in probing exoplanet atmospheres
  • Kramers opacity law: opacity's relation to density and temperature
  • line blanketing: so many bunched spectral lines that they cannot be distinguished
  • Lyman break: abrupt change in galaxy spectrum at the Lyman series wavelength limit
  • Lyman-alpha forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
  • opacity: a measure of opaqueness of a material
  • optical depth: a measure of opaqueness of a path of light
  • oscillator strength: fraction expressing QM's contribution to the probability of absorption
  • photochemistry: study of the chemical effects of light
  • photoionization: photon striking neutral atom expelling an electron
  • self-absorption: EMR absorption by the same substance that emitted it
  • stimulated emission: emission triggered by received photons
  • telluric line: absorption line in ground observation due to Earth atmosphere
• absorption band: see spectral band
  • continuous absorption: the absorption of a whole section of a spectrum
• absorption coefficient: measure of how much light a substance absorbs
  • opacity: a measure of opaqueness of a material
• absorption cross section: see absorption coefficient
  • oscillator strength: fraction expressing QM's contribution to the probability of absorption
• absorption line: dark line within a spectrum
• absorption line galaxy: see emission line galaxy
• absorption nebula (dark nebula): cloud that obscures stars behind it
  • emission nebula: nebula that emits light such as an HII region or PN
• absorption redshift: see redshift
• absorption spectroscopy (transmission spectroscopy): spectrum of radiation passing through a substance
  • cavity-enhanced absorption spectroscopy: passing a beam through a gas multiple times to amplify absorption lines
• absorptivity: see emissivity
  • Kirchhoff's law of thermal radiation: for an object in thermodynamic equilibrium, emissivity equals absorptance
• abstract algebra
• Lie transform: type of infinitesimal transform
• abundance notation (bracket notation): notation for a comparison of an abundance ratio with that of the Sun
• abundance ratio: see abundances
• abundance ratio: see bracket notation
• abundance retrieval: see retrieval
• abundances: relative amounts of each chemical element
  • chemical tagging: using abundances to trace the origin of particular stars
• abundances of the chemical elements (abundances): relative amounts of each chemical element
• AC (Astrographic Catalog): historical star catalog of the whole sky to magnitude 11
• AC: see AGILE
• AC: see double star designation
• AC: see rare designator prefixes
  • telegrapher's equations: two equations describing a transmission line
• ACA: see Atacama Large Millimeter Array
  • Millimeter-wave Intensity Mapping Experiment: project to map CO and [CII]
• Academia Sinica
• Academia Sinica Institute of Astronomy and Astrophysics: Taiwanese astrophysics research organization
• Academia Sinica Institute of Astronomy and Astrophysics: Taiwanese astrophysics research organization
  • East Asian Observatory: operator of JCMT
• ACAM: see William Herschel Telescope
• ACBAR: instrument used in a CMB survey
  • South Pole Station: science station at the South Pole
• ACBAR 2008: see ACBAR
• ACBAR08: see ACBAR
• Accelerating Space Commerce, Exploration, and New Discovery: AIAA interest group
• Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun: see THEMIS
• accelerometer: see gravimetry
• accreting X-ray pulsar (X-ray pulsar): pulsar producing X-rays from accretion
• accretion: enlargement of an astronomical body by gravitationally attracting additional mass
  • accretion disk: disk around an astronomical body of material that is accreting
  • accretion rate: rate of addition of mass to an object
  • black hole accretion rate: measure, especially used for AGNs
  • Bondi radius: radius within which a body moving through a medium will draw it in
  • cold mass accretion: stellar accretion through an accretion disk
  • core accretion model: model for the formation of giant planets
  • epicyclic frequency: frequency of oscillation in an accretion disk
  • gravitational instability model: model for the formation of giant planets
  • magnetospheric truncation radius: radius at which the disc ram pressure matches the magnetic field pressure
  • mass loading: moving gas gaining mass from clouds or stars
  • retrograde accretion: accretion disk spinning in opposite direction to the body
• accretion disk: disk around an astronomical body of material that is accreting
  • Blandford-Payne mechanism: means of by which an accretion disk can power a jet
  • Blandford-Znajek mechanism: means of extracting BH rotational energy by magnetized accretion disk
  • disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
  • jet: stream of matter from an astronomical body
  • magnetic tower: length of twisted magnetic field lines produced by rotating field
  • magnetorotational instability: instability in the fluid of a disk from MHD effects
• accretion induced collapse: see Type Ia supernova
• accretion luminosity: see accretion
• accretion rate: rate of addition of mass to an object
• accretion rate: see accretion
  • autoconversion rate: rate at which water changes from cloud droplets to new raindrops
• accretion runaway: see accretion
• accretor: see mass transfer
• ACE (Advanced Composition Explorer): satellite collecting solar wind and cosmic rays
• ACe consortium: corporations contracted to construct E-ELT
• ACES: a spectrometer used to view the corona during eclipses
  • Air-SPEC: a spectrometer used to view the corona during eclipses
  • ASPIRE: mechanism to stabilize observations from an airplane
• acetylene: compound of two carbon and two hydrogen atoms
• ACH: see rare designator prefixes
• Achernar: ninth-brightest star in the sky
• achondrite: see chondrite
• achondrite: see meteorite
• achromatic transit
• transiting planet: planet crossing between another body and the observer
• acidity: measure of the activity of hydrogen ions in a solution
  • carbonate system: system governing water and CO2 in the presence of each other
• ACIS: imaging spectrometer on Chandra X-ray telescope
• ACIS: see Chandra X-ray Observatory
  • Chandra Deep Field North: X-ray deep survey encompassing HDF region
  • Chandra Deep Field South: X-ray deep survey encompassing HDF-South region
• Ack: see rare designator prefixes
• ACM (Asteroids, Comets, and Meteors): special-interest meeting
• ACO: see Abell Catalog
• ACO 85 (Abell 85): galaxy cluster with central giant elliptical galaxy
• ACOS: see Mauna Loa Solar Observatory
• acoustic frequency: see asteroseismology
• acoustic peak: see baryon acoustic oscillations
• acoustic scale: see baryon acoustic oscillations
• ACP: see Cassini
• ACR (anomalous cosmic rays): cosmic rays with unexpectedly low energies
• ACRIM: see Solar Maximum Mission
• ACRIM2: see Upper Atmosphere Research Satellite
• ACS: see Hubble Space Telescope
• ACS: see INTEGRAL
• ACS: see PHAT
• ACS: see Trace Gas Orbiter
  • Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey: early-universe survey by HST
  • Cosmic Evolution Survey: investigation of dark matter and the universe's large scale structure
  • field of view: angular measure of how much an optical instrument can view
  • Hubble Ultra-Deep Field: extremely detailed HST image of a small region of space
  • Sagittarius Window Eclipsing Extrasolar Planet Search: transit search using HST time
  • Ultraviolet Hubble Ultra-deep Field: ultraviolet data covering the Hubble Ultra Deep Field region of the sky
• ACSIS: see James Clerk Maxwell Telescope
• ACT (Atacama Cosmology Telescope): 6-meter microwave survey telescope in Chile
• ACT: see Hipparcos
  • Atacama Desert: Chilean high-altitude, dry plateau with numerous observatories
  • Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
  • Simons Array: telescope array to map CMB polarization
  • Simons Observatory: CMB observatory on Atacama Desert
• ACT Reference Catalog: see Hipparcos
• ACT Survey
• Atacama Cosmology Telescope: 6-meter microwave survey telescope in Chile
• ACT-RC: see Hipparcos
• actinide: see lanthanide
• actinide nucleosynthesis: see lanthanide
• actinium: see lanthanide
• active BHB: see black hole binary
• active BHMF: see black hole mass function
• active black hole mass function: see black hole mass function
• active comet: see comet
• active galactic nucleus: central region of a galaxy with extremely high luminosity
  • Compton reflection: recognizable emission due to a gas or plasma's Compton scattering
• active galaxy: galaxy with an active, i.e., extremely luminous central region
• Active Magnetospheric Particle Tracer Explorers (AMPTE): three spacecraft experimenting on Earth magnetosphere
• active phase: see symbiotic binary
• activity (stellar activity): transient behavior of a star
• ACTPol: see Atacama Cosmology Telescope
• ACTPol Survey
• Atacama Cosmology Telescope: 6-meter microwave survey telescope in Chile
• D56: a target survey field of ACT telescope
• actuator: telescope control motor
• ACV: see variable star
• ACYG: see pulsating star
  • Rigel: brightest star in constellation Orion
• AD Leo (AD Leonis): active red dwarf
• AD Leonis: active red dwarf
• ADAF (advection dominated accretion flow): accretion without radiating much energy
  • AGN accretion: an SMBH's accretion, such as powers AGNs/quasars
  • alpha disk: well-known model of an accretion disk
• ADAM: procedure to retrieve the shape of an asteroid
• ADAM: see ADAM::THOR
• ADAM::THOR: computerized system for discovering asteroids in observation data
• adaptive alignment: see segmented mirror
• adaptive mesh refinement: numerical modeling method balancing detail with tractability
• adaptive optics: optical mechanism to compensate for varying atmospheric distortion
  • wavefront sensor: instrument for determining a wave's deformation
• adaptive refinement tree: algorithm-type for solving n-body problem
• adaptive-optics (adaptive optics): optical mechanism to compensate for varying atmospheric distortion
• ADBS: see rare designator prefixes
• ADC (Astronomical Data Center): 1980s-1990s NASA/Goddard data archive
• ADC Backend For Bolometer Array: APEX instrument
• ADDGALS: method of galaxy mock-catalog creation
• Adding Density Dependent Galaxies to Lightcone Simulations (ADDGALS): method of galaxy mock-catalog creation
• ADEC: NASA unit to coordinate efforts of data archiving and dissemination
• ADEPT
• Roman Space Telescope: proposed near-infrared space observatory
• ADF (Astrophysics Data Facility): former NASA unit responsible for data from NASA astrophysics missions
• ADI (angular differential imaging): using telescope rotation to suppress speckles
  • speckle suppression: methods of reducing noise in telescope observations
• ADI+RDI: see reference star differential imaging
• adiabatic index: see specific heat
• adiabatic process: process that occurs with no transfer of heat
• ADIS (Astrophysics Data and Information Services): perhaps one-time name for NASA ADF or ADS
• Aditya-L1: 2023 spacecraft viewing Sun and analyzing solar wind
• AdLIGO: see LIGO
• aDM (atomic dark matter): theory of particle dark matter in which they interact
• admittance: effect of atmospheric pressure on gravity
• ADMX (Axion Dark Matter Experiment): a search for axions as potential dark matter particles
• ADMX G2: see Axion Dark Matter Experiment
• ADONIS: see ESO 3.6m Telescope
• ADONIS: see New Technology Telescope
• ADOPT: see Telescopio Nazionale Galileo
• ADP: see Magnetospheric Multiscale Mission
• Adrastea: see shepherd moon
• Adron-RM: see Rosalind Franklin
• ADS (Aitken Double Star Catalogue): 1932 catalog with both multiple-star systems and non-orbiting double stars
• ADS (Astrophysics Data System): online astrophysics bibliography and paper archive
• AdS (anti-de Sitter space): type of curved space
• AdS/CFT correspondence: see holographic duality
• adsorption: adhesion to a surface
• AdvACT: see Atacama Cosmology Telescope
• AdvACT Survey
• Atacama Cosmology Telescope: 6-meter microwave survey telescope in Chile
• Advanced CCD Imaging Spectrometer (ACIS): imaging spectrometer on Chandra X-ray telescope
• Advanced Composition Explorer: satellite collecting solar wind and cosmic rays
• Advanced Dark Energy Physics Telescope
• Roman Space Telescope: proposed near-infrared space observatory
• Advanced LIGO: see LIGO
• 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 Technology Large Aperture Space Telescope: see LUVOIR
• Advanced Technology Solar Telescope (DKIST): 4 m solar telescope at Haleakala Observatory
• Advanced Technology Telescope: see ANU 2.3m Telescope
  • Siding Spring Observatory: observatory in New South Wales, Australia
• Advanced Telescope for High Energy Astrophysics
• ATHENA: planned ESA X-ray space telescope
• Advanced Virgo: see Virgo
• Advanced X-ray Astrophysics Facility (Chandra X-ray Observatory): space X-ray telescope
• Advanced X-ray Imaging Satellite (AXIS): concept for space X-ray observatory
• advection: transport of something through a fluid's motion
• advection dominated accretion flow: accretion without radiating much energy
• advection length scale: see advection
• advection timescale: see advection
  • timescale: general length of time something takes
• advection velocity scale: see advection
• Ae star: see Be star
• AEGIS: early 2000s survey study of distant galaxies
• Aeolis Mons: see Mars Science Laboratory
• aeon (gigayear): a billion years
• aerobraking
• Trace Gas Orbiter: ESA and Russian Mars orbiter-probe launched in 2016
• aerodynamics: see hydrodynamics
• Aeronomy of Ice in the Mesosphere: spacecraft to study upper Earth atmosphere
• aerosols: particles suspended in an atmosphere
• Aesara: see PyMC
• AF2: see William Herschel Telescope
• AFEOV (Association Française des Observateurs d'Étoiles Variables): French organization formed in 1920s
• AFG: see Magnetospheric Multiscale Mission
• AFGL (AFGL Four Color Infrared Sky Survey): 1970s infrared survey
• AFGL (Air Force Geophysics Laboratory): merged into the Air Force Research Laboratory (AFRL)
• AFGL: see AFGL Four Color Infrared Sky Survey
• AFGL Four Color Infrared Sky Survey: 1970s infrared survey
• afrc (Armstrong Flight Research Center): NASA aeronautical research center in California
• Africa Millimetre Telescope: planned 15 m radio telescope array in Namibia
• Africa Millimetre Telescope: see Swedish-ESO Submillimetre Telescope
• AFTA
• Roman Space Telescope: proposed near-infrared space observatory
• afterglow: see gamma-ray burst
• AFWA
• MarsWRF: Mars-oriented general circulation model
• AG (Astronomische Gesellschaft): German astronomical society
• AG: see rare designator prefixes
• Ag: see rare designator prefixes
• AGAPE: see POINT-AGAPE
• AGASA
• Telescope Array Project: cosmic-ray observatory aiming for extremely energetic particles
• AGB (asymptotic giant branch): a second stage of helium burning in some stars
  • blue loop: stellar evolutionary-track segment due to short-term helium burning
  • J-region asymptotic giant branch: standard candle consisting of selected AGB stars
  • post-AGB star: stellar-evolution phase between AGB and white dwarf
• AGB star: see asymptotic giant branch
• AGC (Arecibo General Catalog): catalog of galaxies to support ALFALFA surveys
• AGC: see Abell Catalog
• AGC: see rare designator prefixes
• age
• BaSTI: database relating isochrones to stellar parameters
• coeval: the same age
• Dartmouth Stellar Evolution Database: database relating isochrones to stellar parameters
• galaxy age determination: methods of estimating a galaxy's age
• gyrochronology: means of estimating stellar age from rotation
• Hubble time: approximation of the age of the universe
• isochronal fitting: method of estimating stellar age from retrievable parameters
• isochrone: line of equal ages on an HRD
• lithium depletion boundary: line on HRD dividing stars with lithium and those without
• pulsar characteristic age: approximate age determination of a pulsar based upon rotation rate
• stellar age determination: methods of estimating a star's age
• age of the universe (Hubble time): approximation of the age of the universe
• age of the universe: see Lambda-CDM model
  • Hubble constant: current rate of expansion of the universe
• age-metallicity relation: older stars generally have lower metallicity
  • metallicity: metal fraction of an object
  • stellar population: grouping of stars according to metallicity
• age-velocity-dispersion relation: relation between stellar age and peculiar velocity
• age-velocity-metallicity relation: see velocity-metallicity relation
  • age-metallicity relation: older stars generally have lower metallicity
  • age-velocity-dispersion relation: relation between stellar age and peculiar velocity
• Agena (Beta Centauri): second brightest star in Centaurus
• Agenzia Spaziale Italiana: includes space-based astronomy research
• AGILE: Italian space gamma-ray observatory
• AGK (Astronomische Gesellschaft Katalog): 19th/20th century astrometric catalog
• AGK1: see Astronomische Gesellschaft Katalog
• AGK2: see Astronomische Gesellschaft Katalog
• AGK3: see Astronomische Gesellschaft Katalog
• AGKR: see Astronomische Gesellschaft Katalog
• AGL: see AGILE
• AGN (active galactic nucleus): central region of a galaxy with extremely high luminosity
  • AGN corona: plasma surrounding or near an AGN
  • BASS: survey of AGNs found by the Swift BAT
  • blazar: very compact variable quasar
  • BPT diagram: diagram comparing emission-line ratios for characterizing ionization
  • broad line region: AGN region producing broader lines
  • Compton reflection: recognizable emission due to a gas or plasma's Compton scattering
  • extragalactic astronomy: astronomy of other galaxies, galaxy clusters, AGNs, quasars, etc.
  • galactic wind: wind of charged particles out of some galaxies
  • gas streamer: stream of gas
  • Kepler-Swift Active Galaxies and Stars Survey: X-ray/UV survey of objects within the Kepler field
  • MOJAVE: program to monitor AGN jet radio brightness and polarization
  • narrow line region: AGN region producing narrower lines
  • NGC 7469: spiral galaxy with AGN outflow
  • obscured fraction-luminosity relation: relation between AGN luminosity and surrounding dust IR emission
  • quasar: distant, bright object that appears something like a star
  • reverberation mapping: technique for measuring the size of SMBHs
  • star formation feedback: mechanisms whereby star formation regulates its own rate
  • ultra-fast outflow: characteristic of some AGNs
  • Whirlpool Galaxy: easily-observed spiral galaxy
• AGN accretion: an SMBH's accretion, such as powers AGNs/quasars
• AGN bubble: see active galactic nucleus
• AGN corona: plasma surrounding or near an AGN
• AGN corona: see corona
• AGN feedback: see active galactic nucleus
• AGN feedback: see star formation feedback
• AGN jet: see jet
• AGN microlensing: see gravitational microlensing
• AGN outflow: see active galactic nucleus
• AGPS: see ASCA
• AGU (American Geophysical Union): US organization
• AH03: see rare designator prefixes
• Ahmed: see rare designator prefixes
• AI
• convolutional neural network: type of image processing software
• AIA: see Solar Dynamics Observatory
• AIAA (American Institute of Aeronautics and Astronautics): society of engineers
• AIC (Akaike information criterion): particular formula for comparison of statistical models
• AIC: see Type Ia supernova
• AIC corrected: see Akaike information criterion
• AICc: see Akaike information criterion
• AIM (Aeronomy of Ice in the Mesosphere): spacecraft to study upper Earth atmosphere
• AIM-CO: survey of CO from star-forming epoch
• AIPS (Astronomical Image Processing System): software for processing radio astronomy data
• AIPS++: see Astronomical Image Processing System
• Air Force Geophysics Laboratory: merged into the Air Force Research Laboratory (AFRL)
• Air Force Geophysics Laboratory: see AFGL Four Color Infrared Sky Survey
• 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 by incoming particle or EMR
  • Cherenkov detector: type of high energy photon or particle detector
• Air-SPEC: a spectrometer used to view the corona during eclipses
  • ACES: a spectrometer used to view the corona during eclipses
  • ASPIRE: mechanism to stabilize observations from an airplane
• airborne
• ACES: a spectrometer used to view the corona during eclipses
• Air-SPEC: a spectrometer used to view the corona during eclipses
• ARCADE: balloon-borne centimeter-wavelength surveyor
• Archeops: balloon-borne 1.3 m submillimeter telescope
• ASPIRE: mechanism to stabilize observations from an airplane
• ASTHROS: balloon-borne 2.5-m submillimeter telescope
• BLAST: balloon-borne 1.8-m submillimeter telescope
• BOOMERanG: 1990s-2000s balloon-borne 1.3-meter millimeter telescope
• BUSS: 1970s balloon-based ultraviolet astronomy mission
• CIBER: sounding-rocket survey of near-infrared background
• COSI: 2000s balloon-based gamma ray telescope
• EBEX: balloon-based CMB polarization survey
• ESIS: EUV spectrograph for solar corona observation
• EUSO-SPB: balloon-borne cosmic ray observatory
• EXCLAIM: planned balloon-borne 70-cm telescope with spectrometers
• Galileo Observatory: 1960s-1970s infrared observatory aircraft
• GUSTO: balloon-borne 0.9-m far-infrared telescope
• Kuiper Airborne Observatory: 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
• SCAP: 1980s balloon-borne ultraviolet telescope
• SOFIA: aircraft-based infrared observatory
• SPIDER: 2015 balloon-borne observatory to observe CMB polarization
• STUDIO: balloon-borne 0.5 m ultraviolet telescope
• SUNRISE: balloon-borne 1 m solar telescope
• SuperBIT: balloon-borne 0.5-m telescope
• Taurus­: balloon-borne polarimeter to study the CMB
• TIM: planned balloon-borne 2 m telescope and spectrometer
• TopHat: 2001 balloon -based CMB survey
• Airborne Coronal Emission Surveyor (ACES): a spectrometer used to view the corona during eclipses
  • Air-SPEC: a spectrometer used to view the corona during eclipses
  • ASPIRE: mechanism to stabilize observations from an airplane
• Airborne Infrared Spectrometer (Air-SPEC): a spectrometer used to view the corona during eclipses
• Airborne Spectro-Polarization Infrared Experiment: see ASPIRE
• Airborne Stabilized Platform for Infrared Experiments (ASPIRE): mechanism to stabilize observations from an airplane
  • ACES: a spectrometer used to view the corona during eclipses
• 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: see Galaxy Evolution Explorer
• Aitken Double Star Catalogue: 1932 catalog with both multiple-star systems and non-orbiting double stars
• AJ (Astronomical Journal): American Astronomical Society journal
• Akaike information criterion: particular formula for comparison of statistical models
• AKARI: Japanese space infrared telescope
  • Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• Akeno Giant Air Shower Array
• Telescope Array Project: cosmic-ray observatory aiming for extremely energetic particles
• AL: see NIRCam
• Al (aluminum): element, Al, atomic number 13
• Al: see rare designator prefixes
• Alabama
• Automated Lunar and Meteor Observatory: ground observatory in Alabama to record Moon-meteoroid impacts
• ALaMO (Automated Lunar and Meteor Observatory): ground observatory in Alabama to record Moon-meteoroid impacts
• albedo: measure of reflectance
  • earthshine: reflected and emitted electromagnetic radiation from Earth
• albedo feature: see albedo
• Albion
• Kuiper Belt: further part of solar system beyond Neptune
• Alcaino: see rare designator prefixes
• Alcock-Paczyński effect: type of distortion of the apparent depth of galaxy clusters
• Alcock-Paczyński test: see Alcock-Paczyński effect
• ALD: see rare designator prefixes
• ALESS: see LABOCA Extended Chandra Deep Field-South Submillimetre Survey
• ALESS: see submillimeter galaxy designator
• Alessi: see rare designator prefixes
• ALEXIS: 1990s soft X-ray transient monitor
• ALFA: see Arecibo Observatory
  • ALFALFA: HI survey of many galaxies
  • PALFA: Arecibo search for pulsars
• ALFALFA: HI survey of many galaxies
• Alfvén Mach number: see Alfvén wave
• Alfvén Mach number: see Mach number
• Alfvén number: see Alfvén wave
• Alfvén number: see Mach number
• Alfvén point: see Alfvén wave
• Alfvén radius
• neutron star: stellar remnant consisting entirely of solar masses of neutrons
• Alfvén speed: see Alfvén wave
• Alfvén velocity: see Alfvén wave
• Alfvén wave: a type of transverse wave along magnetic field lines in plasma
  • plasma wave: wave incorporating the EM forces within plasma
• Alfven Wave Solar Atmosphere Model: see SWMF
• algebra
• Lie transform: type of infinitesimal transform
• Algol: a multiple-star system demonstrating effects of mass transfer
  • binary star: system of two stars co-orbiting
• Algol paradox: see Algol
• Algol variable: see Algol
• Algol variable: see variable star
• Algols: see Algol
• Algonquin Radio Observatory: 46 meter radio telescope
• algorithm
• adaptive refinement tree: algorithm-type for solving n-body problem
• HARM²: technique for parallelizing computations of radiation with hydrodynamics
• Alicante: see rare designator prefixes
• ALICE: see Rosetta
• Alice: see New Horizons
• aLIGO: see LIGO
• Alinda
• asteroid family: set of asteroids based on similar orbits
• Aliqa Uma stream
• Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
• alkane: see hydrocarbon
• alkene: see hydrocarbon
• alkyne: see hydrocarbon
• all sky
• 87GB Catalog of Radio Sources: 1980s Green Bank radio survey
• A Broadband Imaging X-ray All-sky Survey: failed 1999 space mission
• AFGL Four Color Infrared Sky Survey: 1970s infrared survey
• AIM-CO: survey of CO from star-forming epoch
• AKARI: Japanese space infrared telescope
• All Sky Automated Survey: Polish survey of 20 million objects brighter than 14 magnitude
• All Sky Automated Survey for SuperNovae: survey of both hemispheres for supernovae
• APASS: down to 16 magnitude
• APOGEE: SDSS near-infrared survey of stars
• Badgerys Creek Interferometer 101-MHz Survey: early 1950s survey of southern-hemisphere radio sources
• blind survey: survey conducted independently of prior information
• C-BASS: 6 cm survey of the entire sky
• Campo Imperatore Near-Earth Object Survey: survey of near-Earth objects
• Catalina Sky Survey: survey of near-Earth objects
• Cosmic Lens All-sky Survey: 1990s/2000s radio survey aimed at gravitational lensing
• CRATES: catalog of 8.4 GHz data on radio sources
• DENIS: 1990s southern sky survey of two near-infrared bands
• Digitized Sky Survey: digitization of Palomar and UK Schmidt plates
• Dominion Observatory 10.03 MHz Source Catalog: 1960s survey of northern-hemisphere radio sources
• Dominion Observatory 1420 MHz Source Catalog: 1960s survey of northern-hemisphere radio sources
• eROSITA: Russian/German space X-ray telescope launched in 2019
• ESO/Uppsala Survey of the ESO (B) Atlas: 1970s southern all-sky survey
• Fourth Cambridge Catalog of Radio Sources: 1960s catalog of northern hemisphere 178 MHz sources
• Gaia: astrometry survey satellite launched in 2013
• Galactic All-sky Survey: HI survey of the Milky Way
• Galactic Emission Mapping: radio sky survey
• GMAN: collaboration to alert on microlensing transients
• Green Bank 6-cm Radio Source Catalog: catalog of from 1980s northern-hemisphere radio survey
• Hamburg Schmidt Survey: photographic plates from the Hamburg Schmidt Camera
• HATNet: distributed array of telescopes to search for transients
• HI 4-Pi Survey: HI map based upon EBHIS and GASS
• HI Jodrell All-Sky Survey: northern-hemisphere HI survey carried out in late 90s/early 2000s
• HIPASS: HI survey carried out 1997 to 2002
• KELT: pair of telescopes that searched for transients
• LINEAR: survey of near-Earth objects
• LONEOS: survey of near-Earth objects
• MASCARA: distributed array of telescopes to search for exoplanets
• NEAT: survey tracking near-Earth objects
• NGTS: survey of transits from Chile
• NRAO VLA Sky Survey: 1990s microwave survey of 82% of the sky
• Ohio Radio Survey: 1960s radio survey by Ohio State University
• Palomar Observatory Sky Survey: 1950s photographic plates from Palomar 48 inch telescope
• Palomar Transient Factory: survey designed to find transients
• Pan-STARRS: set of survey telescopes
• Parkes Catalog: catalog of from 1960s-1990 of radio sources in southern hemisphere
• Parkes-MIT-NRAO Surveys: 1990 southern-hemisphere radio surveys
• POLARBEAR: instrument to map CMB polarization
• Rosat Bright Survey: list of bright X-ray sources from ROSAT observations
• Rosat Hard Survey: list of hard X-ray sources from ROSAT observations
• ROTSE: automated array of telescopes to uncover and track transients
• Second Byurakan Survey: 1970s-1990s survey of galaxies and quasars
• Simons Array: telescope array to map CMB polarization
• SIMP: 2000s infrared proper-motion survey
• SkyMapper Southern Survey: digital survey of the southern hemisphere sky
• Sloan Digital Sky Survey: imaging survey of 500,000,000 objects in 35% of sky
• SPHEREx: all-sky spectral survey space-mission plan
• SuperWASP: broad Earth-based search for transiting planets
• Texas Survey of Radio Sources at 365 MHz: 1970s/1980s radio survey made with the Texas Interferometer
• Tianlai Project: 21-cm line intensity mapping project
• Trans-Atlantic Exoplanet Survey: 2000s exoplanet-search survey using three telescopes
• Two Micron All-sky Survey: near-infrared survey of both hemispheres
• UK Schmidt Survey: photographic survey of the southern hemisphere sky
• WASP: multi-university initiative to locate transiting planets
• Wide-field Infrared Survey Explorer: infrared space telescope aimed at an all-sky survey
• XO Project: initiative to search for transiting planets
• Zwicky Transient Facility: survey designed to find transients
• All Sky Automated Survey: Polish survey of 20 million objects brighter than 14 magnitude
• All Sky Automated Survey for SuperNovae: survey of both hemispheres for supernovae
• all sky survey
• survey field: portion of the celestial sphere where a survey's observations aim
• All-Data Asteroid Modeling: see ADAM::THOR
• All-Data Asteroid Modelling (ADAM): procedure to retrieve the shape of an asteroid
• All-Sky Compiled Catalogue: 2001 catalog compiled from modern sources
• All-wavelength Extended Groth Strip International Survey (AEGIS): early 2000s survey study of distant galaxies
• Allen Telescope Array: array of radio telescopes in northern California for SETI
  • Hat Creek Radio Observatory: California observatory with the Allen Telescope Array
• Aller: see rare designator prefixes
• ALMA (Atacama Large Millimeter Array): advanced millimeter-telescope array in Chile
• ALMA: see DSHARP
• ALMA: see MAPS
  • ALMA-PILS Survey: millimeter survey of a protostar
  • ALMACAL: galaxy survey using ALMA calibration observations
  • ASPECS: millimeter survey of HUDF
  • Atacama Desert: Chilean high-altitude, dry plateau with numerous observatories
  • European Southern Observatory: organization operating telescopes in the southern hemisphere
  • Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
  • Millimeter-wave Intensity Mapping Experiment: project to map CO and [CII]
  • MORA: high resolution 2-mm survey of a portion of the COSMOS field
  • National Radio Astronomy Observatory: US radio astronomy organization
  • REBELS: survey of star-forming galaxies during the reionization
• ALMA Protostellar Interferometric Line Survey (ALMA-PILS Survey): millimeter survey of a protostar
• ALMA Prototype Antenna (ARO 12m Telescope): twelve meter microwave telescope at KPNO
• ALMA Spectroscopic Survey in the Hubble UDF (ASPECS): millimeter survey of HUDF
• ALMA-LESS: see LABOCA Extended Chandra Deep Field-South Submillimetre Survey
  • submillimeter galaxy designator: designation system of submillimeter galaxies
• ALMA-PILS Survey: millimeter survey of a protostar
• ALMA-T
• Academia Sinica Institute of Astronomy and Astrophysics: Taiwanese astrophysics research organization
• ALMACAL: galaxy survey using ALMA calibration observations
• almost dark galaxy: see dark galaxy
• Alnilam
• Orion: well-known constellation in the northern hemisphere
• ALONG: see NIRCam
• Alopeke: see Gemini Observatory
• ALP: see axion
• alpha (alpha particle): essentially a helium nucleus produced by radioactivity
• alpha abundance: see alpha-enhanced
• Alpha Aurigae (Capella): brightest star in Auriga
• 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: see Alpha Centauri
• Alpha Centauri B: see Alpha Centauri
• Alpha Centauri C: see Alpha Centauri
• alpha CO: ratio of CO emissions to H₂
• Alpha Cygni variable (BA supergiant): very bright giant star
• Alpha Cygni variable: see pulsating star
  • Rigel: brightest star in constellation Orion
• alpha decay: see alpha particle
• alpha decay: see radioactive decay
  • radioactivity: an unstable nucleus's tendency to change through emission of particles
• alpha disk: well-known model of an accretion disk
  • advection dominated accretion flow: accretion without radiating much energy
• alpha element: element created by alpha capture
  • alpha-enhanced: metallicity with a high percentage of alpha elements
  • iron peak element: element near the iron peak
• alpha enhancement: see alpha-enhanced
  • [α/Fe] versus [Fe/H] diagram: diagram indicating stars' degree of alpha enhancement
• Alpha Eridani (Achernar): ninth-brightest star in the sky
• alpha ladder (alpha process): synthesis of elements through alpha capture
• Alpha Lyrae (Vega): brightest star in constellation Lyra
• Alpha Magnetic Spectrometer (AMS-02): particle detector on ISS
• Alpha Orionis (Betelgeuse): second brightest star in constellation Orion
• alpha particle: essentially a helium nucleus produced by radioactivity
  • alpha capture: combination of a nucleus and an incoming alpha particle
  • alpha element: element created by alpha capture
  • alpha process: synthesis of elements through alpha capture
  • particle spectrometer: device to determine the characteristics of incoming particles
  • radioactive decay: changes in atomic nuclei that happen over time
  • radioactivity: an unstable nucleus's tendency to change through emission of particles
• alpha poor: see alpha-enhanced
• alpha poor disk: see alpha-enhanced
• alpha process: synthesis of elements through alpha capture
  • magnesium: element, Mg, atomic number 12
  • neon: element, Ne, atomic number 10
• alpha rays
• radioactive heating: a source of heat of some planets and moons
• alpha rich (alpha-enhanced): metallicity with a high percentage of alpha elements
• alpha rich disk: see alpha-enhanced
• alpha species (alpha element): element created by alpha capture
• Alpha² Canum Venaticorum variable: see variable star
• alpha-enhanced: metallicity with a high percentage of alpha elements
  • alpha element: element created by alpha capture
• alpha-to-iron ratio: see alpha-enhanced
• ALPO (Association of Lunar and Planetary Observers): international scientific organization
• ALS: see rare designator prefixes
• Alstadi
• ACe consortium: corporations contracted to construct E-ELT
• alt-azimuth mount (altazimuth mount): simple two-axis telescope mount
• Alt/Az system (horizontal coordinate system): celestial coordinate system based upon horizon and north
• Altair: see Gemini Observatory
• altazimuth mount: simple two-axis telescope mount
  • equatorial mount: telescope mount with axis parallel to Earth's
• altazimuth system (horizontal coordinate system): celestial coordinate system based upon horizon and north
• altazimuth telescope: see altazimuth mount
• alternating current
• telegrapher's equations: two equations describing a transmission line
• alternative cosmologies: cosmological models other than Big Bang/Lambda-CDM
• altitude: see horizontal coordinate system
  • altazimuth mount: simple two-axis telescope mount
• altitude-azimuth mount (altazimuth mount): simple two-axis telescope mount
• aluminium (aluminum): element, Al, atomic number 13
• aluminum: element, Al, atomic number 13
  • CAI: calcium/aluminum specs in chondrites
  • cosmic dust: dust in space such as interstellar dust
  • globular cluster: spherical group of stars orbiting a galaxy
• AM (Arp-Madore Catalog of Southern Peculiar Galaxies): 1970s-1980s catalog from the UK Schmidt Survey
• AM: see rare designator prefixes
• AM Herculis star: see variable star
• Am star: A-type star with metallic lines
• Am-Fm: see chemically peculiar star
• AMANDA: see IceCube
  • South Pole Station: science station at the South Pole
• AMASE (Astrophysics Multi-spectral Archive Search Engine): 1990s search tool
• Amaterasu particle
• Oh-My-God Particle: extremely energetic particle from space detected in 1991
• amateur
• American Association of Variable Star Observers: organization of amateur observers of variable stars
• Astrolux: historically popular amateur telescope
• GPX: amateur effort to uncover exoplanets within the galactic plane
• International Variable Star Index: variable star catalog by AAVSO
• amateur astronomer: see amateur astronomy
• Amateur Astronomers Association of New York: American organization
• amateur astronomy: astronomy carried out as a hobby
• amateur telescope: see amateur astronomy
• Amateur Telescope Making: abbreviation for the activity
• AMBER: see European Southern Observatory Very Large Telescope
• AME (anomalous microwave emission): component of microwave background discovered in the 1990s
  • spinning dust emission: source of microwave signal
• American Association of Variable Star Observers: organization of amateur observers of variable stars
  • APASS: down to 16 magnitude
• American Astronomical Society: American organization
• American Geophysical Union: US organization
• American Institute of Aeronautics and Astronautics: society of engineers
• American Meteor Society: meteor-science promotion organization
• American Museum of Natural History: NYC museum carrying out research including astrophysics
• American National Standards Institute: USA standards organization
• American Physical Society: American physics organization
• American Workshop on Cometary Astronomy: renamed to be international, i.e., IWCA
• AMES Research Center: NASA lab in silicon valley
• AMI (Arcminute Microkelvin Imager): pair of microwave arrays
• AMI (aperture masking interferometry): interferometry by means of a single telescope with a mask
  • James Webb Space Telescope: 6.5-meter infrared space telescope at L2
  • Mullard Radio Astronomy Observatory: radio observatory near Cambridge, UK
• AMI LA: see Arcminute Microkelvin Imager
• AMI Large Array: see Arcminute Microkelvin Imager
• AMI SA: see Arcminute Microkelvin Imager
• AMI Small Array: see Arcminute Microkelvin Imager
• AMiBA (Yuan-Tseh Lee Array): microwave interferometer in Hawaii
• AMICA: see Infrared Telescope Maffei
• AMIE: see SMART-1
• amine: type of compound containing nitrogen
• amino acid
• glycine: 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: particular compound of nitrogen and hydrogen
  • amine: type of compound containing nitrogen
• ammonium hydroxide
• hydroxyl: one hydrogen atom and one oxygen atom bound together
• AMNH (American Museum of Natural History): NYC museum carrying out research including astrophysics
• Amor: see near-Earth object
• amorphous galaxy: see irregular galaxy
  • galaxy classification: morphological classification of galaxies
• amorphous ice: see ice
  • snow line: distance from protostar so cool that water condenses
• amorphous ice snow line: see snow line
• amorphous-to-crystal ice transition radius: see snow line
• AMOS: Advanced Maui Optical and Space Surveillance Technologies Conference
• amount of substance
• diffusion: the spreading of particles toward an even distribution
• amp
• siemens: SI unit of electrical conductance
• ampere
• siemens: SI unit of electrical conductance
• Ampere's law
• Maxwell's equations: four equations describing electricity and magnetism
• amplitude: the height of a wave
• amplitude interferometer
• optical interferometer: interferometer of visible light
• amplitude spectral density: see spectral density
• AMPTE: three spacecraft experimenting on Earth magnetosphere
• AMPTE-CCE: see AMPTE
• AMPTE-IRM: see AMPTE
• AMPTE-UKS: see AMPTE
• AMR (adaptive mesh refinement): numerical modeling method balancing detail with tractability
• AMR (age-metallicity relation): older stars generally have lower metallicity
  • stellar population: grouping of stars according to metallicity
• AMS (American Meteor Society): meteor-science promotion organization
• AMS: see AMS-02
• AMS-01: see AMS-02
• AMS-02: particle detector on ISS
• AMT (Africa Millimetre Telescope): planned 15 m radio telescope array in Namibia
• AMT: see Swedish-ESO Submillimetre Telescope
• amu (dalton): mass unit used on atomic scale
  • mean molecular weight: measurement of a gas usual for approximating in gas models
• Amundsen-Scott South Pole Station (South Pole Station): science station at the South Pole
• AMUSE²: survey of ELANs
• AN (Astronomische Nachrichten): German scientific publication
• An: see lanthanide
• ANAIS-112: dark matter detection experiment in Spain
• analog computer: see numerical methods
• analysis
• analytical methods: using solved equations rather than a lot of arithmetic
• interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
• spectral density: strength of power or energy as a function of frequency
• analyte: see titration
• analytical methods: using solved equations rather than a lot of arithmetic
  • numerical methods: using equations through repetitive arithmetic
• anastigmat: optics avoiding common aberrations
• anastigmatic lens: see anastigmat
• ancient
• Hipparchus: Greek astronomer who developed concept of magnitude
• And: see Andromeda
• And I
• Andromeda: spiral galaxy in the Local Group
• ANDES: see European Extremely Large Telescope
• Andrews-Lindsay: see rare designator prefixes
• Andromeda: spiral galaxy in the Local Group
  • Giant Stellar Stream: extensive stellar stream in M31
  • Milkomeda: future galaxy resulting from merger of Milky Way and Andromeda
  • PHAT: HST survey of M31 stars
  • shell galaxy: galaxy with one or more surrounding layers of brightness
• Andromeda Galaxy Amplified Pixels Experiment: see POINT-AGAPE
• Andromeda I
• Andromeda: spiral galaxy in the Local Group
• Andromeda II
• Andromeda: spiral galaxy in the Local Group
• Andromeda subgroup
• galaxy subgroup: a major galaxy and its satellites
• Andromeda-Milky Way collision: see Milkomeda
• anemic galaxy: see spiral galaxy
• angle
• arcsecond: a 3600th of an angular degree
• angle of incidence
• Snell's law: optical principle of refraction
• angle of refraction
• Snell's law: optical principle of refraction
• Anglo-Australian Telescope: 3.9-m reflector telescope in Australia
  • Dark Energy Survey: survey aimed at mapping the universe's expansion
  • DEVILS: visible-light spectrographic survey of 56k distant galaxies
  • GALAH: survey of Milky Way with an emphasis on old structures
  • Siding Spring Observatory: observatory in New South Wales, Australia
  • Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
  • Uppsala-ESO Survey of Asteroids and Comets: 1990s comet and asteroid survey
• angstrom: unit of length 10^-10 meters
• angular acoustic scale: see baryon acoustic oscillations
• angular area (solid angle): three-dimensional analog of an angle
  • field of view: angular measure of how much an optical instrument can view
• angular degree: see arcsecond
• angular diameter: diameter of astronomical object in terms of its angle across the sky
• angular diameter: see angular distance
• angular diameter distance
• redshift-angular size relation: how observed size of an object depends on its redshift
• angular differential imaging: using telescope rotation to suppress speckles
  • antenna pattern: a radio telescope's pattern of directional sensitivity
  • speckle suppression: methods of reducing noise in telescope observations
• angular distance: measure of an angle across the sky
  • position angle: indication of a direction across the celestial sphere
• angular frequency: see frequency
• angular hour: see arcsecond
• angular hour: see right ascension
• angular magnification: a magnification measure for a magnifier with an eyepiece
• angular momentum
• electron shell: radius-level around an atomic nucleus at which electrons can orbit
• retrograde orbit: orbit opposite the usual direction
• specific angular momentum: absolute angular momentum divided by mass
• angular power spectrum: method of characterizing the CMB
• angular radius: see angular distance
  • precession of the equinoxes: Earth axial precession with a 26000-year cycle
• angular resolution: measure of a telescope's ability to distinguish spatial detail
  • parallax: angle due to different lines of sight
  • point source: celestial object that focuses to a point or single Airy disk
• angular size: see angular distance
• angular size-redshift relation (redshift-angular size relation): how observed size of an object depends on its redshift
• angular two-point correlation
• angular power spectrum: method of characterizing the CMB
• angular velocity
• magnetorotational instability: instability in the fluid of a disk from MHD effects
• stellar rotation: rotation of a star around an axis through the middle
• angular wavenumber: see wavenumber
• anion: see ion
  • nitrite: ion of a nitrogen atom and two oxygen atoms with extra electron
• ANIR: see University of Tokyo Atacama Observatory
• anisotropic: see anisotropy
• anisotropic explosion: see anisotropy
  • SN 1987A: supernova in February 1987 rare for being visible by the naked eye
• anisotropy: directional-dependence such as temperature variation around the CMB
  • CMB anisotropies: variations in the spectrum of the CMB
  • isotropy: uniformity in all directions
• Anlitak
• Orion: well-known constellation in the northern hemisphere
• annihilation: see antimatter
  • dark matter annihilation: particle/antiparticle annihilation of WIMPs
  • Majorana particle: theoretical particle that is its own antiparticle
• annual modulation: see dark matter detector
• anomalistic year: planet's time between successive periapses
• anomalistic year: see sidereal
• anomalous cosmic rays: cosmic rays with unexpectedly low energies
• anomalous microwave emission: component of microwave background discovered in the 1990s
  • spinning dust emission: source of microwave signal
• anomalous X-ray pulsar: X-ray pulsars with no high-mass companion
  • magnetar: neutron star with a strong magnetic field
• Anon: see Reference Catalogue of Bright Galaxies
• Anon: see rare designator prefixes
• anorthite
• CAI: calcium/aluminum specs in chondrites
• ANS (Astronomical Netherlands Satellite): 1970s X-ray/ultraviolet space telescope
• ANSI (American National Standards Institute): USA standards organization
• Antalova: see rare designator prefixes
• Antarctic Circle: see circle of latitude
• Antarctic Muon And Neutrino Detector Array: see IceCube
• Antarctica
• High Elevation Antarctic Terahertz Telescope: 61 cm FIR telescope in Antarctica
• Infrared Telescope Maffei: 80 cm infrared telescope in Antarctica
• South Pole Station: science station at the South Pole
• ANTARES: see KM3NeT
• antenna noise temperature (antenna temperature): a type of measure of the noise introduced by an antenna
• antenna pattern: a radio telescope's pattern of directional sensitivity
• antenna temperature: a type of measure of the noise introduced by an antenna
• Anthropocene era: theorized geological era substantially influenced by human activity
• anti-de Sitter space: type of curved space
• anticenter (galactic anticenter): direction opposite the galactic center
  • Anticenter Shell: nebula at edge of Milky Way
• Anticenter Shell: nebula at edge of Milky Way
• Anticenter Superbubble (Anticenter Shell): nebula at edge of Milky Way
• anticharge: see strong force
• antielectron (positron): electron-like antimatter particle with electric charge of +1
  • 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
  • Bethe-Heitler process: type of pair production interaction near nuclei
  • dark matter annihilation: particle/antiparticle annihilation of WIMPs
  • pair production: creation of a particle/antiparticle pair
  • positron: electron-like antimatter particle with electric charge of +1
• Antimatter Spectrometer: see AMS-02
• antineutrino
• antimatter: similar to normal matter but with opposite electrical charge
• antineutron
• antimatter: similar to normal matter but with opposite electrical charge
• positron: electron-like antimatter particle with electric charge of +1
• antiparticle: see antimatter
  • dark matter annihilation: particle/antiparticle annihilation of WIMPs
  • Majorana particle: theoretical particle that is its own antiparticle
• Antipin: see rare designator prefixes
• antiproton
• antimatter: similar to normal matter but with opposite electrical charge
• positron: electron-like antimatter particle with electric charge of +1
• antiquark: see quark
  • antimatter: similar to normal matter but with opposite electrical charge
  • particle: very small thing
• Antlia II
• Milky Way subgroup: the Milky Way and its satellites
• Antlia SN Remnant: dispersed supernova remnant in the constellation Antlia
• Antlia SNR (Antlia SN Remnant): dispersed supernova remnant in the constellation Antlia
• Antlia Supernova Remnant (Antlia SN Remnant): dispersed supernova remnant in the constellation Antlia
• Antu Telescope: see European Southern Observatory Very Large Telescope
• ANU
• Siding Spring Observatory: observatory in New South Wales, Australia
• ANU 2.3-m Telescope
• Siding Spring Observatory: observatory in New South Wales, Australia
• ANU 2.3m Telescope: 2.3-m telescope at Siding Spring Observatory
• ANU 40-inch Telescope
• Lupus Transit Survey: survey for hot Jupiters in a region of constellation Lupus
• Siding Spring Observatory: observatory in New South Wales, Australia
• AO (Arecibo Occultation Survey): 1960s radio survey using occultations by the Moon
• AO (adaptive optics): optical mechanism to compensate for varying atmospheric distortion
• AO188: see Subaru Telescope
• AO3000: see Subaru Telescope
• AO36: see Subaru Telescope
• AO3K: see Subaru Telescope
• AOF: see European Southern Observatory Very Large Telescope
• AOSA (Arecibo Observatory Space Academy): Arecibo pre-college program
• AOT (astronomical observation request): term for a proposal to use a telescope
• Ap: see rare designator prefixes
• AP effect (Alcock-Paczyński effect): type of distortion of the apparent depth of galaxy clusters
• Ap star: peculiar type of A star
  • chemically peculiar star: star with SED showing presence metals unusual for stars
• APA (ARO 12m Telescope): twelve meter microwave telescope at KPNO
• Apache Point Observatory
• APOGEE: SDSS near-infrared survey of stars
• Milky Way Mapper: SDSS spectrographic survey of Milky Way stars
• Sloan 2.5m Telescope: telescope for SDSS in New Mexico
• Sloan Digital Sky Survey: imaging survey of 500,000,000 objects in 35% of sky
• TripleSpec: near-infrared spectrograph on the Hale Telescope
• Apache Point Observatory Galactic Evolution Experiment (APOGEE): SDSS near-infrared survey of stars
• apapsis: see apsis
• APASS: down to 16 magnitude
• apastron: see apsis
• APD: see Geiger-avalanche photodiode
• APERTIF: see Westerbork Synthesis Radio Telescope
• aperture: opening through which light passes
  • collecting area: cross-sectional area over which a telescope receives EMR
• aperture array: see phased array
• aperture mask: see aperture masking interferometry
• aperture masking (aperture masking interferometry): interferometry by means of a single telescope with a mask
• aperture masking interferometry: interferometry by means of a single telescope with a mask
  • James Webb Space Telescope: 6.5-meter infrared space telescope at L2
• aperture photometry: method of determining the brightness of an imaged star
• aperture synthesis: interferometry to simulate a larger aperture telescope
  • baseline: distance between dishes of an interferometer
  • interferometer: device detecting EMR properties using interference between waves
  • Low-frequency Array: low frequency radio telescope
• APEX (Atacama Pathfinder Experiment): 12-meter submillimeter telescope in Chile
  • Atacama Desert: Chilean high-altitude, dry plateau with numerous observatories
  • CONCERTO: spectrometer aimed at mapping the [CII] line
  • DeGaS-MC: APEX survey of potential star formation regions in the Magellanic Clouds
  • European Southern Observatory: organization operating telescopes in the southern hemisphere
  • LABOCA Extended Chandra Deep Field-South Submillimetre Survey: submillimeter survey of a well-studied piece of sky
  • Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
• APEx (Atmospheric Physics of Exoplanets): MPIAA department
• APEX-1: see Atacama Pathfinder Experiment
• APEX-2: see Atacama Pathfinder Experiment
• APEX-2A: see Atacama Pathfinder Experiment
• APEX-3: see Atacama Pathfinder Experiment
• APEX-T2: see Atacama Pathfinder Experiment
• APF (Automated Planet Finder): robotic telescope to find exoplanets using RV method
  • Lick Observatory: California observatory of long standing
  • TESS-Keck Survey: Keck follow-up survey to TESS discoveries
• APG (Atlas of Peculiar Galaxies): 1960s catalog-book with photos
• aphelion: see apsis
  • astronomical unit: about 93 million miles
• API: application programming interface
• ApJ (Astrophysical Journal): American Astronomical Society scientific publication
• ApJL (Astrophysical Journal Letters): American Astronomical Society scientific publication
• ApJS (Astrophysical Journal Supplement Series): American Astronomical Society scientific publication
• APM (plate measuring machine): machine to measure position of images on photographic plates
• APM: see APM Galaxy Survey
  • Large Bright QSO Survey: 1980s quasar survey
• APM Galaxy Survey: 1990s survey of galaxies in southern sky
• APM QSO Survey (Large Bright QSO Survey): 1980s quasar survey
• APMPM: see rare designator prefixes
• APMUKS (APM Galaxy Survey): 1990s survey of galaxies in southern sky
• APO
• APOGEE: SDSS near-infrared survey of stars
• Milky Way Mapper: SDSS spectrographic survey of Milky Way stars
• Sloan 2.5m Telescope: telescope for SDSS in New Mexico
• Sloan Digital Sky Survey: imaging survey of 500,000,000 objects in 35% of sky
• TripleSpec: near-infrared spectrograph on the Hale Telescope
• APO 3.5m Telescope
• CorMASS: near-infrared spectrograph
• APO Galactic Evolution Experiment: see Sloan Digital Sky Survey
• apoapse: see apsis
• apoapsis: see apsis
  • eccentricity: degree to which an orbit is non-circular
• apocenter: see apsis
• APOD (Astronomy Picture of the Day): NASA general education initiative
• apodization: improving telescope images by manipulating diffraction
• apodize
• apodization: improving telescope images by manipulating diffraction
• apogalacticon: see apsis
• APOGEE: SDSS near-infrared survey of stars
• APOGEE: see Sloan Digital Sky Survey
  • Sloan 2.5m Telescope: telescope for SDSS in New Mexico
• apogee: see apsis
• APOGEE Library of Infrared SSP Templates (A-LIST): catalog of templates of H-band spectra for SPS
• APOGEE Spectrograph: see Sloan 2.5m Telescope
  • fiber positioner: machine to set up fibers in multi-object spectrograph
  • Milky Way Mapper: SDSS spectrographic survey of Milky Way stars
• APOGEE-1: see APOGEE
• APOGEE-2: see APOGEE
• APOGEE-2: see Sloan Digital Sky Survey
  • MaNGA Stellar Library: catalog of SEDs of representative stars
• APOGEE-II
• APOGEE: SDSS near-infrared survey of stars
• APOGEE-N
• APOGEE: SDSS near-infrared survey of stars
• APOGEE-S
• APOGEE: SDSS near-infrared survey of stars
• Apohele: see near-Earth object
• Apollo: see near-Earth object
• apparent binary (optical double): double star where the two are not gravitationally bound
  • binary star: system of two stars co-orbiting
• apparent bolometric magnitude
• apparent magnitude: magnitude as seen from Earth adjusted for Earth atmosphere
• bolometric magnitude: absolute magnitude of all wavelengths
• apparent diameter (angular diameter): diameter of astronomical object in terms of its angle across the sky
• apparent dimension: see angular distance
• apparent elastic thickness (elastic thickness): measure of the thickness of a sagging layer of a planet surface
• apparent magnitude: magnitude as seen from Earth adjusted for Earth atmosphere
• apparent radiant: see meteoroid
• Approximate Bayesian Computation: shortcut-method in Bayesian statistics
• Approximate Places of Double Stars in the Southern Hemisphere (Dunlop Double Star Catalogue): 1829 catalog of double stars viewed from Australia
• appulse: moment of apparent nearest distance of observed bodies
• APS (American Physical Society): American physics organization
• APS: see Lunar Prospector
• apsis: closest or furthest point in an eccentric orbit
• APT (Automated Patrol Telescope): 0.5 m telescope at Siding Spring Observatory
• APXS: see Mars Exploration Rover
• APXS: see Mars Pathfinder
• APXS: see Mars Science Laboratory
• aqueous solution
• acidity: measure of the activity of hydrogen ions in a solution
• Arab Union for Astronomy and Space Sciences: has hosted conferences
• Arakelian Catalog: 1970s list of small/bright galaxies
• Araki Telescope
• WINERED: near-infrared non-cryogenic spectrograph
• ARC (AMES Research Center): NASA lab in silicon valley
• ARC (Astrophysical Research Consortium): owns Apache Point Observatory
• arc
• arcsecond: a 3600th of an angular degree
• ARC 3.5m
• TripleSpec: near-infrared spectrograph on the Hale Telescope
• ARCADE: balloon-borne centimeter-wavelength surveyor
• ARCADE 2: see ARCADE
• Archeops: balloon-borne 1.3 m submillimeter telescope
• Arches: see rare designator prefixes
• Archinaut: see OSAM-1
• Archival Legacy Program: see legacy survey
• archive
• Canadian Astronomy Data Centre: online data distribution
• HEASARC: NASA archive of data on high energy astronomy
• MAST: archive of data from surveys and missions
• arcmin: see arcsecond
• arcminute: see arcsecond
  • right ascension: direction coordinate along celestial equator
• Arcminute Cosmology Bolometer Array Receiver (ACBAR): instrument used in a CMB survey
• Arcminute Microkelvin Imager: pair of microwave arrays
  • Mullard Radio Astronomy Observatory: radio observatory near Cambridge, UK
• ARCoIRIS: see SOAR Telescope
• ARCoIRIS: see TripleSpec
• ARCoIRIS: see Víctor M. Blanco Telescope
• arcsec (arcsecond): a 3600th of an angular degree
• arcsecond: a 3600th of an angular degree
  • right ascension: direction coordinate along celestial equator
• Arctic Circle: see circle of latitude
• Arcturus: fourth brightest star in the sky
• Arcus: X-ray space telescope plan aiming for 2031 launch
• areal coordinate system: coordinate system based upon a known triangle
• Arecibo (Arecibo Observatory): former large 305 m radio telescope in Puerto Rico
• Arecibo 305-Meter Telescope: see Arecibo Observatory
• Arecibo General Catalog: catalog of galaxies to support ALFALFA surveys
• Arecibo L-band Feed Array: see Arecibo Observatory
• Arecibo Observatory: former large 305 m radio telescope in Puerto Rico
  • ALFALFA: HI survey of many galaxies
  • Arecibo Occultation Survey: 1960s radio survey using occultations by the Moon
  • European VLBI Network: consortium of radio telescopes to coordinate VLBI efforts
  • FAST: Arecibo-like 500 m telescope in China
  • Galactic All-sky Survey: HI survey of the Milky Way
  • NANOGrav: effort to detect gravitational waves through pulsar timing
  • PALFA: Arecibo search for pulsars
  • RESOLVE­: galaxy and gas survey limited to 65-100 Mpc
• Arecibo Observatory Space Academy: Arecibo pre-college program
• Arecibo Occultation Survey: 1960s radio survey using occultations by the Moon
• Arecibo Pulsar ALFA Survey (PALFA): Arecibo search for pulsars
• Arecibo Telescope (Arecibo Observatory): former large 305 m radio telescope in Puerto Rico
• Arecibo Telescope: see Arecibo Observatory
• arene: see hydrocarbon
• AREPO: cosmology simulation using moving mesh technique
• Ares Vallis
• Mars Pathfinder: 1990s mission to Mars with rover
• Arfa-E: see Kvant 1
• ARG: see double star designation
• Argentina
• Pierre Auger Observatory: cosmic-ray observatory in Argentina
• QUBIC: survey measuring the polarization of the CMB
• ARGO-YBJ Experiment: cosmic-ray/gamma-ray detector in Tibet
• ARGOS: 1999 technology-research satellite
• ARGOS: see Large Binocular Telescope
• argument of periapsis: see apsis
• argument of periapsis: see orbital element
• argument of pericenter: see apsis
• argument of perifocus: see apsis
• argument of perihelion: see apsis
• ARGUS: see European Southern Observatory Very Large Telescope
• Argus: see Green Bank Telescope
• Argus Array: see Evryscope
• Argus Pathfinder: see Evryscope
• Ariane
• Space Launch System: launch rocket in development, e.g., for future astronomical projects
• ARIBIB: online astronomy/astrophysics bibliography
• ARIEL: planned space mission for exoplanet spectrography
• Ariel: see Uranus
  • moon: a planet's natural satellite, such as Earth's
• Ariel 5: 1970s X-ray space telescope
  • ARIEL: planned space mission for exoplanet spectrography
• Ariel 6
• ARIEL: planned space mission for exoplanet spectrography
• Ariel Program
• ARIEL: planned space mission for exoplanet spectrography
• ARIES: see MMT
• Arizona
• ARO 12m Telescope: twelve meter microwave telescope at KPNO
• Fred Lawrence Whipple Observatory: observatory near Amado, Arizona
• Hiltner Telescope: 2.4-meter reflector telescope at MDM observatory
• IOTA: past optical interferometer in Arizona
• Kitt Peak National Observatory: NOIRLab observatory in Arizona with Mayall telescope
• Large Binocular Telescope: dual 8.4 meter telescope in Arizona
• Lowell Discovery Telescope: 4.3 m telescope at Lowell Observatory, Arizona
• Lowell Observatory: Arizona observatory of long standing
• Mayall 4m Telescope: 4 meter reflector telescope at Kitt Peak
• Mimir: multi-function near-infrared instrument on Perkins Telescope
• MMT: 6.5 meter telescope at Mt. Hopkins, Arizona
• Navy Precision Optical Interferometer: optical interferometer in Arizona
• Submillimeter Telescope: 10-meter far-infrared telescope
• T4 Automated Photometric Telescope: automated 75-cm telescope to a long-term star monitoring survey
• USNO: observatory obtaining astronomical data for Naval use
• VERITAS: ground gamma ray telescope array in Arizona
• WIYN 3.5m Telescope: Kitt Peak telescope run by university collaboration and NOIRLab
• Arizona Radio Observatory
• ARO 12m Telescope: twelve meter microwave telescope at KPNO
• Submillimeter Telescope: 10-meter far-infrared telescope
• Arjuna: see near-Earth object
• Ark (Arakelian Catalog): 1970s list of small/bright galaxies
• Armstrong Flight Research Center: NASA aeronautical research center in California
• ARO (Algonquin Radio Observatory): 46 meter radio telescope
• ARO: see rare designator prefixes
  • ARO 12m Telescope: twelve meter microwave telescope at KPNO
• ARO 12m Telescope: twelve meter microwave telescope at KPNO
  • National Radio Astronomy Observatory: US radio astronomy organization
• ARO 36 foot telescope
• ARO 12m Telescope: twelve meter microwave telescope at KPNO
• aromatic hydrocarbon: see hydrocarbon
• aromatic hydrocarbon: see polycyclic aromatic hydrocarbon
• Arp: see Atlas of Peculiar Galaxies
• Arp Atlas of Peculiar Galaxies (Atlas of Peculiar Galaxies): 1960s catalog-book with photos
• Arp Catalog of Peculiar Galaxies (Atlas of Peculiar Galaxies): 1960s catalog-book with photos
• Arp-Madore Catalog of Southern Peculiar Galaxies: 1970s-1980s catalog from the UK Schmidt Survey
• array
• Allen Telescope Array: array of radio telescopes in northern California for SETI
• Arcminute Microkelvin Imager: pair of microwave arrays
• Atacama Large Millimeter Array: advanced millimeter-telescope array in Chile
• Australia Telescope Compact Array: radio telescope in eastern Australia
• Australian Square Kilometre Array Pathfinder: radio telescope array of 36 12-meter dishes
• BIMA telescope: millimeter interferometer in operation 1985 to 2005
• Carbon Monoxide Mapping Array: planned experiment to observe epoch of reionization
• CHARA: optical interferometer on Mount Wilson
• Cherenkov Telescope Array: ground gamma-ray telescope array in development
• Combined Array for Research in Millimeter-wave Astronomy: former array of radio telescopes in eastern California
• Darwin: past plan for space telescopes acting as an interferometer
• Dragonfly Telephoto Array: Canadian compact array of small visible-light telescopes
• European VLBI Network: consortium of radio telescopes to coordinate VLBI efforts
• Event Horizon Telescope: growing VLBI network
• Evryscope: automated array of telescopes to uncover transients
• Giant Metrewave Radio Telescope: large radio interferometer in India
• HATNet: distributed array of telescopes to search for transients
• HERA: low frequency radio telescope
• High Energy Stereoscopic System: ground gamma-ray telescope array
• HIRAX: radio telescope array for 21-cm surveying
• IOTA: past optical interferometer in Arizona
• Long Wavelength Array: radio telescope in New Mexico
• Low-frequency Array: low frequency radio telescope
• MAGIC: ground gamma-ray telescope array in the Canary Islands
• MASCARA: distributed array of telescopes to search for exoplanets
• MASTER Robotic Net: network of automated telescopes to identify transients
• MeerKAT: new radio telescope in South Africa
• MERLIN: VLBI array spread across England
• MRO Interferometer: optical interferometer in New Mexico
• Murchison Widefield Array: low frequency radio telescope
• Narrabri Stellar Intensity Interferometer: 1960s optical interferometer for measuring stellar diameters
• Next Generation Very Large Array: planned radio telescope array as a follow-on to ALMA and the Jansky VLA
• Northern Extended Millimeter Array: large radio telescope array under construction in Europe
• OVRO-LWA: radio telescope in California
• Pan-STARRS: set of survey telescopes
• Plateau de Bure Interferometer: 6-dish interferometer in French Alps
• 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
• Square Kilometre Array: planned radio telescope with square-kilometer collecting area
• STARE: array of radio telescopes monitoring radio transients
• Submillimeter Array: radio interferometer in Hawaii
• Sunyaev-Zel'dovich Array: array of eight 3.5 meter microwave telescopes
• SUSI: optical interferometer in Australia
• VERA: VLBI project to map the Milky Way
• VERITAS: ground gamma ray telescope array in Arizona
• Very Large Array: radio telescope in New Mexico
• Very Long Baseline Array: radio interferometer stretching 8000 km
• Very Small Array: radio interferometer in Canary Islands
• Westerbork Synthesis Radio Telescope: radio telescope array of 14 dishes in Netherlands
• Yuan-Tseh Lee Array: microwave interferometer in Hawaii
• Array for Microwave Background Anisotropy (Yuan-Tseh Lee Array): microwave interferometer in Hawaii
• 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 (adaptive refinement tree): algorithm-type for solving n-body problem
• ART-P: see GRANAT
• ART-S: see GRANAT
• ARTEMIS: simulations of Milky-Way-like galaxy halos
• ARTEMIS: see THEMIS
• Artemis (Artemis program): NASA's program in development to send people to the moon
• Artemis: see Space Launch System
• Artemis program: NASA's program in development to send people to the moon
• artificial intelligence
• convolutional neural network: type of image processing software
• artificial satellite: see moon
• ARX-XC: see Spektr-RG
• arXiv: website with physics paper preprints
• arXiv.org (arXiv): website with physics paper preprints
• AS: see NIRCam
• AS: see rare designator prefixes
• AS 209
• MAPS: ALMA survey researching planet-formation
• ASA (Astronomical Society of the Atlantic): interested parties promoting astronomy
• ASAS (All Sky Automated Survey): Polish survey of 20 million objects brighter than 14 magnitude
• ASAS telescope
• Haleakala Observatory: observatory on Maui, Hawaii
• Las Campanas Observatory: observatory in southern Atacama Desert
• ASAS-SN (All Sky Automated Survey for SuperNovae): survey of both hemispheres for supernovae
• ASASSN (All Sky Automated Survey for SuperNovae): survey of both hemispheres for supernovae
• ASASSN telescopes
• Haleakala Observatory: observatory on Maui, Hawaii
• ASCA: 1990s Japanese space X-ray telescope
• ASCA Galactic Plane Survey: see ASCA
• ASCC (All-Sky Compiled Catalogue): 2001 catalog compiled from modern sources
• ASCC-2.5 (All-Sky Compiled Catalogue): 2001 catalog compiled from modern sources
• ASCEND (Accelerating Space Commerce, Exploration, and New Discovery): AIAA interest group
• ascending node: see orbital element
• ASCL (Astrophysics Source Code Library): collection of astrophysics programs
• ASD: see spectral density
• ASHORT: see NIRCam
• ASI (Agenzia Spaziale Italiana): includes space-based astronomy research
  • AGILE: Italian space gamma-ray observatory
  • Cassini: explorer spacecraft sent to Saturn
• ASI/MET: see Mars Pathfinder
• Asia
• East Asian Core Observatories Association: promotes astronomy
• East-Asian Planet Search Network: initiative to find exoplanets
• ASIAA (Academia Sinica Institute of Astronomy and Astrophysics): Taiwanese astrophysics research organization
  • East Asian Observatory: operator of JCMT
• ASIAA Intensity Mapping for CO (AIM-CO): survey of CO from star-forming epoch
• Asiago Observatory
• Asiago Supernova Catalog: catalog of known supernovae and their galaxies
• Asiago Supernova Catalog: catalog of known supernovae and their galaxies
• ASKAP (Australian Square Kilometre Array Pathfinder): radio telescope array of 36 12-meter dishes
• ASM: see Ariel 5
• ASM: see Ginga
• ASM: see RXTE
• ASP (Astronomical Society of the Pacific): general astronomy-education organization
  • Publications of the Astronomical Society of the Pacific: monthly journal
• ASPECS: millimeter survey of HUDF
• ASPERA: see Mars Express
• ASPERA-4: see Venus Express
• ASPEX: see Aditya-L1
• aspheric lens: see aspheric mirror
• aspheric mirror: mirror with other than a spherical curvature
  • Schwarzschild telescope: type of two-mirror reflector telescope
• aspherical mirror (aspheric mirror): mirror with other than a spherical curvature
• ASPIRE: mechanism to stabilize observations from an airplane
  • ACES: a spectrometer used to view the corona during eclipses
• ASR: see rare designator prefixes
• associated Legendre functions: see Legendre polynomials
• associated Legendre polynomials: see Legendre polynomials
• association (stellar association): like a large open cluster but even less tightly bound
• Association Française des Observateurs d'Étoiles Variables: French organization formed in 1920s
• Association of Lunar and Planetary Observers: international scientific organization
• Association of Universities for Research in Astronomy: collaboration of universities operating observatories
• AST (NSF AST): US government astronomical research funding division
• ASTE (Atacama Submillimeter Telescope Experiment): 10-meter submillimeter telescope in Chile
  • Atacama Desert: Chilean high-altitude, dry plateau with numerous observatories
  • DESHIMA: submillimeter spectrometer
  • Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
  • transition edge sensor: sensor using superconductivity's strong temperature sensitivity
• ASTE Band8: see Atacama Submillimeter Telescope Experiment
• 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
  • 2010 TK₇: asteroid that is an Earth Trojan
  • Ceres: dwarf planet and largest asteroid
  • Psyche: asteroid discovered in 1852
• asteroid belt: ring of orbiting planetoids/asteroids
  • asteroid: minor planet without comet characteristics
  • planetoid: an asteroid or physically similar body
• Asteroid Discovery, Analysis, and Mapping: see ADAM::THOR
• asteroid family: set of asteroids based on similar orbits
• asteroid occultation: see occultation observations
• Asteroid Terrestrial-impact Last Alert System (ATLAS survey): survey to find NEOs
• asteroids
• ADAM: procedure to retrieve the shape of an asteroid
• ADAM::THOR: computerized system for discovering asteroids in observation data
• asteroid belt: ring of orbiting planetoids/asteroids
• asteroid family: set of asteroids based on similar orbits
• Bisei Asteroid Tracking Telescope for Rapid Survey: Japanese telescope surveying to find NEOs and space junk
• Committee for Small-Body Nomenclature: early 2000s IAU division since replaced by WG-SBN
• CONTOUR: failed 2002 NASA astroid flyby mission
• Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
• Deep Space 1: 1998-2001 mission to fly by asteroid
• Giotto: 1980s space mission carrying out a Comet Halley flyby
• Hayabusa2: JAXA mission that returned a sample of an asteroid
• Hubble Asteroid Hunter: Zooniverse effort to find asteroids in HST images
• International Monitoring Programs for Asteroid and Comet Threat: 1999 IAU-sponsored conference in Italy
• Kirkwood gap: gaps in asteroid orbital radii corresponding to Jupiter resonances
• Lucy: space probe to observe Jupiter Trojan asteroids
• minor planet: lesser solar system body without comet characteristics
• NEAR Shoemaker: space mission to an asteroid
• OSIRIS-REx: space mission aiming to return a sample of an asteroid
• Palomar-Leiden Survey: 1960s survey to identify distant asteroids
• Psyche: space mission on its way to asteroid Psyche
• solar system object: the Sun, solar system planets, minor planets, comets, and moons
• Steward Observatory Asteroid Relational Database: 1980s/1990s repository of asteroid data
• Uppsala-ESO Survey of Asteroids and Comets: 1990s comet and asteroid survey
• Asteroids, Comets, and Meteors: special-interest meeting
• asteroseismology: study of stars through analysis of their pulsation
  • GYRE: a stellar oscillation code
  • normal mode: resonant surface waves in seismology
  • PLATO: planned observatory-satellite aimed at finding exoplanets
  • Wide Field Infrared Explorer: partly-failed 1999 infrared satellite
• asterosphere: see heliosphere
  • stellar wind: gas or plasma emanating from a star
• ASTHROS: balloon-borne 2.5-m submillimeter telescope
• astigmatism: focusing differently according to direction across the focal plane
  • aberration: types of flaws in telescope images
  • three-mirror anastigmat: general type of reflector telescope
• Astrid simulation: cosmological simulation over z = 99 to 3
• ASTRO (Autonomous Space Transport Robotic Operations): experiment re robotic satellite servicing/refueling in space
• Astro: see Gaia
• Astro G: see HALCA
• Astro-1
• Hopkins Ultraviolet Telescope: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
• Ultraviolet Imaging Telescope: 1990s ultraviolet space telescope used on two Space Shuttle missions
• Wisconsin Ultraviolet Photo-polarimeter Experiment: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
• Astro-2
• Hopkins Ultraviolet Telescope: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
• Ultraviolet Imaging Telescope: 1990s ultraviolet space telescope used on two Space Shuttle missions
• Wisconsin Ultraviolet Photo-polarimeter Experiment: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
• ASTRO-A
• Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• ASTRO-B
• Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• ASTRO-C (Ginga): 1980s Japanese space X-ray telescope
  • Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• ASTRO-D
• Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• Astro-D (ASCA): 1990s Japanese space X-ray telescope
• ASTRO-EII (Suzaku): space X-ray telescope
• ASTRO-F (AKARI): Japanese space infrared telescope
• Astro-H (Hitomi): 2016 Japanese space X-ray telescope
  • CSA: includes astronomical research
  • XRISM: X-ray space telescope launched in 2023
• ASTRO-H Successor (XRISM): X-ray space telescope launched in 2023
• ASTRO-H2 (XRISM): X-ray space telescope launched in 2023
• Astro-Rivelatore Gamma a Immagini Leggero (AGILE): Italian space gamma-ray observatory
• Astro2010: The Astronomy and Astrophysics Decadal Survey: see decadal survey
• Astro2020: initiative suggesting major survey efforts over the 2020-2030 decade
• Astroaccesible: project to make astronomy information available to the blind
• AstroBEAR: MHD simulation system
• AstroBetter: site with shared research tips.
• AstroBetter Rumor Mill: list of open astrophysics jobs
• astrobiology: study of extra-terrestrial life
  • biofluorescence: common fluorescence in organisms to dissipate harmful UV radiation
  • biosignature: sign of life
  • Carl Sagan Institute: group researching finding life on other planets and moons
  • Drake equation: estimate of advanced life in the Milky Way
  • Enceladus Life Finder: mission to search for life on Saturn moon Enceladus
  • Enceladus Orbilander: concept for a NASA mission to Enceladus
  • geosignature: geological sign of consequences of life
  • Lego principle: principle that life is associated with a skew in molecule abundances
  • molecular handedness: mirror-imaged variants of some molecules
  • NASA Astrobiology Institute: former research funding and coordination organization
  • reducing atmosphere: atmosphere lacking oxygen and other oxidizers
  • technosignature: sign of technology
  • vegetation red edge: wavelength cut-off point in the reflectivity of typical plants
• Astrobites: online informal summaries of astrophysics papers
• Astrocats: software to create and manage an astronomy catalog
  • MOSFiT: code to match light-curves with light-curve models
• astrograph: telescope designed for astrometry and other precise position measurements
• Astrographic Catalog: historical star catalog of the whole sky to magnitude 11
• Astrographic Catalog / Tycho: see Hipparcos
• Astrographic Chart (Astrographic Catalog): historical star catalog of the whole sky to magnitude 11
• astrolabe: ancient instrument to determine to date, time, and location information from the sky
• astrolabe: see Danjon astrolabe
• astrology
• astronomical symbol: traditional symbols specific to astronomy, for Sun, Earth, etc.
• 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
  • All-Sky Compiled Catalogue: 2001 catalog compiled from modern sources
  • angular distance: measure of an angle across the sky
  • astrograph: telescope designed for astrometry and other precise position measurements
  • astrometric binary: binary star system detected by observing the movement of a star
  • Astronomische Gesellschaft Katalog: 19th/20th century astrometric catalog
  • Carlsberg Meridian Catalogue: series of astrometric catalogs from 19th century on
  • Catalogues of Fundamental Stars: series of astrometric catalogs from 19th century on
  • celestial reference frame: frame of reference associated with a catalog of stars or quasars
  • Full-sky Astrometric Mapping Explorer: early 2000s proposal for an astrometric space telescope
  • Gaia: astrometry survey satellite launched in 2013
  • Gaia Celestial Reference Frame: celestial reference frame based upon Gaia data
  • GaiaNIR: concept for a Gaia follow-on including NIR astrometry
  • Guide Star Astrometric Support Package: software to assist in using guide stars for HST observations
  • Hipparcos: ESA astrometry space observatory circa 1990
  • Hipparcos Celestial Reference Frame: astronomical reference frame based upon Hipparcos catalog
  • ICRF: celestial reference frame based upon quasars
  • meridian circle: instrument for timing the passage of stars over a meridian
  • NOMAD: astrometric star catalog
  • plate measuring machine: machine to measure position of images on photographic plates
  • proper motion: apparent motion in relation to the position of the Sun
  • réseau: grid on photographic plate to assist in astrometry
  • USNO: observatory obtaining astronomical data for Naval use
  • USNO CCD Astrograph Catalog: USNO star catalog including proper motions
  • USNO Twin Astrograph: USNO astrograph deployed in 1970
  • VERA: VLBI project to map the Milky Way
• ASTRON: Netherlands radio astronomy research organization
  • Low-frequency Array: low frequency radio telescope
  • Westerbork Synthesis Radio Telescope: radio telescope array of 14 dishes in Netherlands
• Astron 2 (GRANAT): observatory-satellite for detecting gamma rays and X-rays
• Astronet: European astronomy consortium
• astronomer
• Hipparchus: Greek astronomer who developed concept of magnitude
• Astronomer's Telegram: service reporting transients and discoveries
• Astronomia nova: Johannes Kepler's book about investigating Mars' orbit
• astronomical aberration: see aberration
• astronomical body (astronomical object): planet, star, galaxy, etc.
• astronomical catalog: list of observed astronomical bodies including characteristics
• Astronomical Data Center: 1980s-1990s NASA/Goddard data archive
• astronomical event: see celestial event
• Astronomical Image Processing System: software for processing radio astronomy data
• Astronomical Journal: American Astronomical Society journal
• Astronomical Netherlands Satellite: 1970s X-ray/ultraviolet space telescope
• astronomical object: planet, star, galaxy, etc.
• astronomical observation request: term for a proposal to use a telescope
• astronomical quantities: some astronomy amounts/numbers
• astronomical scintillation (twinkling): blinking, apparent movement and color changes of observed stars
• Astronomical Society of the Atlantic: interested parties promoting astronomy
• Astronomical Society of the Pacific: general astronomy-education organization
  • Publications of the Astronomical Society of the Pacific: monthly journal
• astronomical source (source): astronomical object producing some observed signal
• astronomical survey: project collecting astronomical data
• astronomical surveys
• astronomical catalog: list of observed astronomical bodies including characteristics
• astronomical symbol: traditional symbols specific to astronomy, for Sun, Earth, etc.
• astronomical transient (transient): observed change in the sky
  • supernova designator: typical designation of supernovae
• astronomical unit: about 93 million miles
• Astronomische Gesellschaft: German astronomical society
  • Astronomische Gesellschaft Katalog: 19th/20th century astrometric catalog
• Astronomische Gesellschaft Katalog: 19th/20th century astrometric catalog
• Astronomische Nachrichten: German scientific publication
• astronomy: study of astronomical objects and their environments
  • AAS Job Register: directory of astrophysics jobs
  • amateur astronomy: astronomy carried out as a hobby
  • Amateur Telescope Making: abbreviation for the activity
  • angular diameter: diameter of astronomical object in terms of its angle across the sky
  • angular distance: measure of an angle across the sky
  • appulse: moment of apparent nearest distance of observed bodies
  • asterism: easily recognizable star pattern
  • Astroaccesible: project to make astronomy information available to the blind
  • astrometry: precise measurement of the position and movement of stars
  • Astronomical Journal: American Astronomical Society journal
  • astronomical object: planet, star, galaxy, etc.
  • astronomical unit: about 93 million miles
  • astrophysics: physics applied to astronomy
  • barycenter: center of mass of two orbiting bodies
  • Bayer designation: star designation consisting of a Greek letter and constellation name
  • blind survey: survey conducted independently of prior information
  • cadence: period between observations
  • CASA: software package for radio interferometry image generation
  • celestial event: something astronomical occurring visibly in the sky
  • celestial navigation: navigating such as across the sea, using the stars
  • celestial sphere: the sky in considered as a sphere surrounding the observer
  • Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference: IAU initiative to address the issue of satellite constellations
  • 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: three-dimensional array of numerical data
  • data release: publication or distribution of a set of data from a survey
  • double star designation: systems and format of double star designators
  • EAS Job Directory: directory of astrophysics jobs
  • Eddington bias: selection bias from mistaking something common for something rare
  • El Universo en palabras: Series of audios produced by Astroaccesible
  • 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 covering some area of the sky
  • 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: determination of the more northern direction of the Milky Way's axis
  • Great Debate: historical debate regarding the nature of galaxies
  • guest observer: non-affiliated researcher welcomed to use an observatory
  • guest star: translation of ancient Chinese term for a visible transient
  • guide star: star used to assist in astronomical observation
  • HEAD: AAS division supporting X-ray and gamma-ray astrophysics
  • heliocentric system: model of the universe with the planets orbiting the Sun
  • high time-resolution astrophysics: second-by-second observation of/for transients
  • inferior conjunction: conjunction of an "inferior planet", Venus or Mercury
  • interferometry: analysis of superimposed EMR waves
  • International Astronomical Union: association of professional astronomers
  • International Dark-Sky Association: organization promoting control of light pollution
  • International Earth Rotation and Reference Systems Service: service monitoring Earth's rotation and precession
  • International Geophysical Year: 1957-1958 initiative for geophysical and related astronomical research
  • International Halley Watch: initiative to coordinate observation of Halley's Comet in 1986
  • International Scientific Optical Network: project to track objects in space
  • 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: unit of measurement of spectral flux density
  • LAD: AAS division supporting laboratory work relevant to astrophysics
  • 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: 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
  • localization: ability to identify location of a transient
  • low frequency radio astronomy: astronomy using the lower end of the radio spectrum
  • Lutz-Kelker bias: measurement bias due to unbalanced parallax uncertainties
  • 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
  • NELM: naked eye limiting magnitude
  • 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
  • optical transient: transient evident from visible light observation
  • orrery: mechanical device to simulate the solar system
  • panchromatic: involving all colors, i.e., all wavelengths
  • parsec: 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 using optical filters
  • plane of the sky: plane tangent to the celestial sphere
  • planetary science: study of planet characteristics
  • polarimetry: measurement of polarization of EMR
  • positional astronomy: calculation methods for relating sky position to position in space
  • primary: central body of a system such as the Sun within 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
  • RAS JobList: directory of astrophysics jobs
  • 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
  • sky quality meter: device to measure the brightness/magnitude of the sky itself.
  • Society of Amateur Radio Astronomers: US organization
  • solar luminosity: luminosity unit representing the luminosity of the Sun
  • solar mass: mass unit representing the mass of the Sun
  • solar neutrino unit: 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: astronomical body shining from fusion energy
  • 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
  • superior conjunction: conjunction of an "superior planet", Mars, Jupiter, etc.
  • supernova designator: typical designation of supernovae
  • supernova light curve: changing intensity of light following a supernova
  • 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
  • time-domain astronomy: observing and analyzing changes in astronomical objects
  • Titius-Bode law: relationship between the distances between solar system planets
  • TLM: magnitude of the dimmest astronomical object you can see
  • tracer: chemical whose detection indicates the presence of something else
  • 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: online database of astronomical data
  • VisieR: online astronomical catalog contents/data
  • volume weighting: method of accommodating the Malmquist bias
  • Working Group on Accessibility and Disability: AAS working group
• Astronomy & Astrophysics: European scientific journal
• Astronomy and Astrophysics in the New Millennium: see decadal survey
• Astronomy Picture of the Day: NASA general education initiative
• Astronomy with a Neutrino Telescope and Abyss Environmental Research: see KM3NeT
• astrophotography
• exposure time: time spent acquiring a signal
• astrophysical disk (disk): rotating disk-shaped object such as disk galaxy or circumstellar disk
• astrophysical dynamo (dynamo): mechanism for generating magnetic fields around astronomical bodies
• astrophysical jet (jet): stream of matter from an astronomical body
• Astrophysical Journal: American Astronomical Society scientific publication
• Astrophysical Journal Letters: American Astronomical Society scientific publication
• Astrophysical Journal Supplement Series: American Astronomical Society scientific publication
• astrophysical maser
• stimulated emission: emission triggered by received photons
• astrophysical neutrino: neutrino from other than Earth or the usual sources
• Astrophysical Research Consortium: owns Apache Point Observatory
• astrophysics: physics applied to astronomy
  • ARIBIB: online astronomy/astrophysics bibliography
  • AstroBetter: site with shared research tips.
  • AstroBetter Rumor Mill: list of open astrophysics jobs
  • Astrobites: online informal summaries of astrophysics papers
  • astronomical quantities: some astronomy amounts/numbers
  • Astrophysics Data System: online astrophysics bibliography and paper archive
  • astropy: general Python package for astrophysical research
  • atomic dark matter: theory of particle dark matter in which they interact
  • binary black hole: pair of co-orbiting black holes
  • black hole binary: binary star in which one is a stellar black hole
  • Blandford-Znajek mechanism: means of extracting BH rotational energy by magnetized accretion disk
  • celestial mechanics: study of forces and motion of celestial objects
  • Centre for Astrophysics and Supercomputing: research center at Swinburne University, Australia
  • Chandrasekhar limit: maximum mass of a white dwarf
  • cold dark matter: one of three classes of "particle dark matter" theory
  • color-color diagram: means of comparing characteristics of stars
  • color-magnitude diagram: graph plotting color index to magnitude
  • 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: very-high-energy particles from beyond the solar system
  • cosmological equation of state: equation of state of dark matter
  • cosmological model: model of the workings and history of the universe
  • critical density: density of the universe which leaves it flat
  • density parameter: ratio of a density with the critical density
  • erg: CGS unit of energy
  • free-fall time: time it would take a body to collapse if unopposed
  • fuzzy dark matter: 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: diagram relating effective temperature to luminosity
  • halo abundance matching: 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: 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 above which gravity will collapse a cloud
  • Kelvin-Helmholtz timescale: 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 can sit
  • Lambda-CDM model: 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
  • Level 5: hyperlinked collection of astrophysics research findings
  • local standard of rest: velocity with respect to our region of the Milky Way
  • local thermodynamic equilibrium: state when temperature variation is too small to matter
  • mass density: mass per unit volume, as opposed to particle density
  • P-Pdot diagram: diagram comparing the rotation and the slowing of pulsars
  • particle physics: physics such as carried out in accelerators
  • peculiar velocity: velocity with respect to local rest
  • plasma astrophysics: includes cosmology, IGM, ISM, HI regions
  • pointed observation: observation of a specific target
  • Poynting-Robertson effect: force that slows dust grains orbiting a star
  • radial velocity: component of velocity toward or away from observer
  • redshift-angular size relation: how observed size of an object depends on its redshift
  • redshift-magnitude relation: how apparent magnitude depends on redshift
  • relativistic astrophysics: physics applicable to cosmology and strong field gravity
  • repulsive dark matter: concept of dark matter that resists extreme dark-matter density
  • retrieval: determining parameters through observation and modeling
  • Roche lobe: region of a body's gravitational influence closest to its competitor
  • 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
  • sub-GeV dark matter: a more-massive type of CDM
  • systemic velocity: average velocity of grouped objects, such as a galaxy
  • tidal locking: locked rotation of an orbiting body
  • Tolman-Oppenheimer-Volkoff limit: maximum mass of a neutron star
  • turn-off point: point in H-R diagram of a cluster where stars turn red
  • wCDM: Big-Bang cosmological model with constant cosmological equation of state
  • Yarkovsky effect: force on spinning, orbiting objects from asymmetric radiation
  • Yarkovsky-O'Keefe-Radzievskii-Paddack effect: rotational effect on asymmetric asteroids
• Astrophysics Data and Information Services: perhaps one-time name for NASA ADF or ADS
• Astrophysics Data Centers Executive Council (ADEC): NASA unit to coordinate efforts of data archiving and dissemination
• Astrophysics Data Facility: former NASA unit responsible for data from NASA astrophysics missions
• Astrophysics Data Service (Astrophysics Data System): online astrophysics bibliography and paper archive
• Astrophysics Data System: online astrophysics bibliography and paper archive
• Astrophysics Focused Telescope Assets
• Roman Space Telescope: proposed near-infrared space observatory
• Astrophysics Multi-spectral Archive Search Engine: 1990s search tool
• Astrophysics Source Code Library: collection of astrophysics programs
• Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths (ASTHROS): balloon-borne 2.5-m submillimeter telescope
• astropy: general Python package for astrophysical research
• AstroSat: Indian observatory satellite
  • CSA: includes astronomical research
• astrosphere: see heliosphere
• asymmetric explosion: see anisotropy
• asymmetrical galaxy: see galactic tide
• asymptotic giant branch: a second stage of helium burning in some stars
  • J-region asymptotic giant branch: standard candle consisting of selected AGB stars
  • post-AGB star: stellar-evolution phase between AGB and white dwarf
• AT (transient): observed change in the sky
• AT: see Australia Telescope Compact Array
• AT: see Long Baseline Array
• AT: see Transient Name Server
  • supernova designator: typical designation of supernovae
• AT2017gfo: see GW170817
• AT2018cow: unusual 2018 optical transient
  • fast blue optical transient: optical transient with rise time under five days
• AT2018lug: see AT2018cow
• AT2019dsg: 2019 TDE undergoing study
• AT2019fdr: see AT2019dsg
• AT2020xnd: see AT2018cow
• ATA (Allen Telescope Array): array of radio telescopes in northern California for SETI
  • Hat Creek Radio Observatory: California observatory with the Allen Telescope Array
• ATA-350: see Allen Telescope Array
• ATA-42: see Allen Telescope Array
• Atacama Astronomical Park: see Llano de Chajnantor Observatory
• Atacama B-Mode Search: 2012-2014 survey of the CMB
• Atacama Compact Array: see Atacama Large Millimeter Array
• Atacama Cosmology Telescope: 6-meter microwave survey telescope in Chile
  • D56: a target survey field of ACT telescope
  • Simons Array: telescope array to map CMB polarization
• Atacama Desert: Chilean high-altitude, dry plateau with numerous observatories
  • Atacama B-Mode Search: 2012-2014 survey of the CMB
  • Atacama Cosmology Telescope: 6-meter microwave survey telescope in Chile
  • Atacama Large Millimeter Array: advanced millimeter-telescope array in Chile
  • Atacama Pathfinder Experiment: 12-meter submillimeter telescope in Chile
  • Atacama Submillimeter Telescope Experiment: 10-meter submillimeter telescope in Chile
  • BlackGEM: telescope array to follow up gravitational wave signals
  • Calán/Tololo Supernova Survey: late 1980s to early 1990s search to redshift 0.1
  • CCAT: 25-meter submillimeter telescope plan for Chile
  • Cerro Tololo Inter-American Observatory: NOIRLab observatory in Chile with Blanco telescope
  • Cherenkov Telescope Array: ground gamma-ray telescope array in development
  • CMB Stage-4: planned 2020s-generation of ground CMB observations
  • Cosmic Background Imager: radio telescope in Chile observing the CMB
  • Dark Energy Survey: survey aimed at mapping the universe's expansion
  • DECaLS: survey imaging part of SDSS footprint with DECam
  • ESO 3.6m Telescope: reflector telescope at La Silla
  • ESO Schmidt Telescope: 1 meter telescope in Chile with a wide field-of-view
  • European Extremely Large Telescope: 39-meter telescope under construction
  • European Southern Observatory: organization operating telescopes in the southern hemisphere
  • European Southern Observatory Very Large Telescope: four 8.2-meter optical telescopes in Chile that can act together
  • Fred Young Submillimeter Telescope: 6-meter submillimeter survey telescope under construction in Chile
  • Giant Magellan Telescope: 24.5 meter telescope under construction
  • La Silla Observatory: Atacama-desert observatory run by ESO
  • La Silla Paranal Observatory: manages three ESO observatory-sites in Chile
  • Las Campanas Observatory: observatory in southern Atacama Desert
  • Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
  • Magellan Telescopes: pair of 6.5 m optical telescopes in Chile
  • Magellanic Clouds Photometric Survey: UBVI survey of the Magellanic Clouds
  • MASCARA: distributed array of telescopes to search for exoplanets
  • NANTEN2: millimeter telescope in Chile
  • New Technology Telescope: 3.58-meter reflector telescope in Chile
  • NGTS: survey of transits from Chile
  • Paranal Observatory: ESO Atacama observatory with ESO VLT
  • POLARBEAR: instrument to map CMB polarization
  • QUIET: survey to measure the polarization of the CMB
  • Rubin Observatory: 8-meter survey reflector telescope under construction in Chile
  • Simons Array: telescope array to map CMB polarization
  • Simons Observatory: CMB observatory on Atacama Desert
  • SPECULOOS: search for Earth-like exoplanets orbiting nearby dim stars
  • Swedish-ESO Submillimetre Telescope: former 15 m radio telescope array in Chile
  • Swope Supernova Survey: survey of low-redshift Type Ia SN light curves
  • University of Tokyo Atacama Observatory: observatory for a 6.5 m infrared telescope under construction
  • Víctor M. Blanco Telescope: 4 meter reflector telescope in Chile
  • VISTA: 4.1 meter telescope in Paranal Observatory in Chile
  • VLT Survey Telescope: survey telescope located at the VLT site
• Atacama Large Area Submillimeter Telescope (AtLAST): concept for submillimeter survey telescope in Chile
• Atacama Large Millimeter Array: advanced millimeter-telescope array in Chile
• Atacama Large Millimeter/Submillimeter Array (Atacama Large Millimeter Array): advanced millimeter-telescope array in Chile
• Atacama Pathfinder Experiment: 12-meter submillimeter telescope in Chile
• Atacama Plateau (Atacama Desert): Chilean high-altitude, dry plateau with numerous observatories
• Atacama Submillimeter Telescope Experiment: 10-meter submillimeter telescope in Chile
  • DESHIMA: submillimeter spectrometer
• ATCA (Australia Telescope Compact Array): radio telescope in eastern Australia
  • Australia Telescope Large Area Survey: radio survey of two survey fields
  • Long Baseline Array: radio interferometer using Australian telescopes
• ATel (Astronomer's Telegram): service reporting transients and discoveries
• ATELAIS: see rare designator prefixes
• Aten: see near-Earth object
• ATHENA: planned ESA X-ray space telescope
• Atira: see near-Earth object
• ATLAS (ATLAS Stellar Model): computer model of a stellar photosphere
• ATLAS (Australia Telescope Large Area Survey): radio survey of two survey fields
• ATLAS: see ATLAS survey
• ATLAS: see VLT Survey Telescope
• Atlas: see shepherd moon
  • Space Launch System: launch rocket in development, e.g., for future astronomical projects
• Atlas 3D: survey of local galaxies
• ATLAS Code (ATLAS Stellar Model): computer model of a stellar photosphere
• Atlas of Galactic Nebulae: 1980s catalog of Milky-Way nebulae
• Atlas of Peculiar Galaxies: 1960s catalog-book with photos
• ATLAS Stellar Model: computer model of a stellar photosphere
• ATLAS stream
• Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
• ATLAS survey: survey to find NEOs
• ATLAS-1
• FAUST: 1990s ultraviolet space telescope used on two Space Shuttle missions
• ATLAS-HKO
• ATLAS survey: survey to find NEOs
• Haleakala Observatory: observatory on Maui, Hawaii
• ATLAS-MLO
• ATLAS survey: survey to find NEOs
• ATLAS18qqn (AT2018cow): unusual 2018 optical transient
• ATLAS3D (Atlas 3D): survey of local galaxies
• ATLAS^3D (Atlas 3D): survey of local galaxies
• ATLAST: see LUVOIR
• AtLAST: concept for submillimeter survey telescope in Chile
• ATM (Amateur Telescope Making): abbreviation for the activity
• atm: unit of pressure
  • torr: unit of pressure approximating a millimeter of mercury on Earth
• ATMO: atmospheric code for exoplanets and brown dwarfs
• atmosphere: gas surrounding astronomical object
• atmosphere (atm): unit of pressure
  • advection: transport of something through a fluid's motion
  • Aeronomy of Ice in the Mesosphere: spacecraft to study upper Earth atmosphere
  • aerosols: particles suspended in an atmosphere
  • airmass: measure of Earth-atmosphere attenuation for a telescope observation
  • ATMO: atmospheric code for exoplanets and brown dwarfs
  • atmosphere formation: capture and modification of a planet's gases
  • atmospheric escape: escape of gas particles from a planet's atmosphere
  • atmospheric model: model to describe or simulate a planet's atmosphere
  • atmospheric temperature profile: the atmosphere's temperature by altitude
  • atmospheric tide: tide-type movement within the atmosphere
  • atmospheric window: frequency bands within which the atmosphere passes EMR
  • autoconversion rate: rate at which water changes from cloud droplets to new raindrops
  • baroclinicity: measure of misalignment of fluid density and pressure
  • beta drift: tendency for a cyclone to drift poleward and westward
  • Brunt-Väisälä frequency: natural frequency of buoyancy waves
  • BT-Settl: model atmosphere of small stars and brown dwarfs
  • cold trap: layer of atmosphere that prevents a gas from escaping by freezing it
  • DISORT: simulation of radiative transfer in an atmosphere
  • dust devil: small whirlwind visible from dust it collects
  • ExoCTK: collection of software for exoplanet observation and analysis
  • exosphere: outer portion of atmosphere so thin that it is not gas-like
  • general circulation model: climate model of a planet's atmosphere or ocean
  • Global-scale Observations of the Limb and Disk: satellite instrument to study ionosphere regarding space weather
  • gravity wave: wave in fluid where restoring force is gravity
  • gray atmosphere: a model atmosphere whose opacity does not depend upon wavelength
  • Hadley cell: circulation pattern of up at the equator, poleward, down, and back
  • helium 1083 nm line: line useful in probing exoplanet atmospheres
  • helium rain: possible source of heat in giant planet atmospheres
  • HITRAN: spectroscopic parameters for modeling atmospheric optics
  • homopause: level of atmosphere up to which components are mixed
  • humidity: amount of water vapor in a portion of the atmosphere
  • hydrodynamic escape: escape of gas particles from atmosphere due to heating
  • intertropical convergence zone: circulation pattern near equator where north and south Hadley cells meet
  • ionosphere: layers of Earth atmosphere with significant ions
  • Jeans escape: type of ongoing escape of gas particles from atmosphere
  • Jeans parameter: ratio measuring a tendency of an atmosphere to escape
  • jet stream: upper-atmosphere narrow west-to-east streams of air
  • Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
  • limb: the edge of an astronomical object as viewed
  • Mars Climate Orbiter: failed Mars 1990s probe
  • MarsWRF: Mars-oriented general circulation model
  • meridional flow: north-south air circulation
  • MITgcm: well-known general circulation model
  • mixing ratio: ratio of two components of a gas
  • National Oceanic and Atmospheric Administration: US meteorology and oceanography agency
  • numerical weather prediction: Earth weather prediction by computer equation-solving and/or simulation
  • one dimensional climate model: atmospheric model ignoring all horizontal motion
  • plane-parallel atmosphere: simplified atmosphere model ignoring its curvature around the body
  • planetary boundary layer: low level of atmosphere affected by ground
  • polar cyclone: storm centered on the pole
  • precipitable water vapor: depth of liquid water equivalent to the atmosphere's water vapor
  • quasi-biennial oscillation: reversal of Earth equatorial prevailing winds roughly every two years
  • radiative forcing: difference between a planet's incoming and outgoing radiation
  • radiative transfer code: computer model of a gas's radiative transfer
  • reducing atmosphere: atmosphere lacking oxygen and other oxidizers
  • Richardson number: measure of fluid stability consisting of ratio of buoyancy and shear
  • ROCKE-3D: rocky-planet-oriented general circulation model
  • Rossby number: ratio of inertial to Coriolis force
  • Rossby radius of deformation: length scale where rotation effects are significant
  • Rossby waves: meandering shifts in the trajectory of high-altitude winds
  • seeing: apparent blurring and twinkling of objects seen through atmosphere
  • Solar Mesophere Explorer: 1980s Earth atmospheric ozone research satellite
  • space weather: varying conditions in space affecting Earth and humans
  • superrotating wind: wind traveling in the same direction as the planet is rotating
  • surface reaction: such as reactions between gas and adjacent liquid
  • TAM: non-gray-RT 3D model of Titan's atmosphere
  • terrestrial gamma-ray flash: gamma rays emitted from Earth lightning storms
  • thermal wind: type of wind due to temperature gradients that vary by altitude
  • TIMED: space probe observing Earth upper atmosphere for solar effects
  • Ultimate Spitzer Phase Curve Survey: investigation of exoplanet atmospheres
  • Upper Atmosphere Research Satellite: 1990s spacecraft to observe Earth ozone layer
  • weathering: changes in surface due to contact with atmosphere
  • zonal flow: east-west air circulation
  • zone: apparent "horizontal" band in an atmosphere
• atmosphere formation: capture and modification of a planet's gases
• atmospheric boundary layer (planetary boundary layer): low level of atmosphere affected by ground
• atmospheric escape: escape of gas particles from a planet's atmosphere
  • Jeans parameter: ratio measuring a tendency of an atmosphere to escape
• atmospheric extinction: see extinction
• atmospheric formation (atmosphere formation): capture and modification of a planet's gases
• atmospheric model: model to describe or simulate a planet's atmosphere
• Atmospheric Physics of Exoplanets: MPIAA department
• Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL): planned space mission for exoplanet spectrography
• atmospheric retention: see atmosphere
  • atmospheric escape: escape of gas particles from a planet's atmosphere
• atmospheric retrieval: see retrieval
• atmospheric scale height: see scale height
• atmospheric temperature profile: the atmosphere's temperature by altitude
• atmospheric tide: tide-type movement within the atmosphere
• atmospheric transparency
• atmospheric window: frequency bands within which the atmosphere passes EMR
• atmospheric window: frequency bands within which the atmosphere passes EMR
  • ionosphere: layers of Earth atmosphere with significant ions
  • passband: range of electromagnetic wavelengths that a filter allows
• ATNF
• ATNF Pulsar Catalogue: online catalog of pulsars
• ATNF PSR Catalogue (ATNF Pulsar Catalogue): online catalog of pulsars
• ATNF Pulsar Catalogue: online catalog of pulsars
• atomic dark matter: theory of particle dark matter in which they interact
• atomic excitation: electrons above the ground state within atoms
• atomic ISM: see interstellar medium
• atomic mass
• dalton: mass unit used on atomic scale
• fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
• atomic mass constant: see dalton
• atomic mass number (mass number): number of nucleons in an atomic nucleus
  • element: class of atom based on its number of protons
• atomic mass unit (dalton): mass unit used on atomic scale
  • mean molecular weight: measurement of a gas usual for approximating in gas models
• atomic number: 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
  • mass number: number of nucleons in an atomic nucleus
  • neutron capture: combination of an atomic nucleus and a neutron
  • radioactive decay: changes in atomic nuclei that happen over time
• atomic orbital: see electron orbital
• atomic weight: see element
• atoms
• alpha capture: combination of a nucleus and an incoming alpha particle
• alpha element: element created by alpha capture
• alpha process: synthesis of elements through alpha capture
• alpha-enhanced: metallicity with a high percentage of alpha elements
• atomic excitation: electrons above the ground state within atoms
• Auger effect: atom's emission of an electron along with a photon
• beta decay: radioactivity such that an electron or positron is emitted
• Bohr model: has electrons circling nucleus in quantized orbits
• bracket notation: notation for a comparison of an abundance ratio with that of the Sun
• carbon burning: fusion reaction starting with carbon
• degree of ionization: fraction of material consisting of ions
• deuterium burning: any fusion reaction starting with deuterium
• electron capture: combination of an electron with a proton
• electron orbital: a nucleus's "locations" where an electron can orbit
• Fermi sea: atom's minimal-energy electrons filling its lower shells
• fine structure: separate spectral lines due to electron spin and relativistic effects
• fluorescence: emission from a molecule excited by absorption
• forbidden line: spectral line that quantum mechanics disallows for the most part
• fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
• helium burning: fusion reaction starting with helium
• hydrogen burning: any fusion reaction starting with hydrogen
• hyperfine structure: spectral lines from magnetic and spin interactions between electrons and nucleus
• ion: non-neutral atom or molecule, with missing or extra electrons
• iron peak: peak in the distribution of abundances surrounding iron
• iron peak element: element near the iron peak
• lanthanide: element having atomic number within 57 through 71
• lithium burning: any fusion reaction starting with lithium
• metal: in astrophysics, any element more massive than helium
• metallicity: metal fraction of an object
• metastable: characteristic of an excited state that lasts longer than typical
• neon burning: fusion reaction starting with neon
• neutron capture: combination of an atomic nucleus and a neutron
• neutron drip: neutrons exiting from nuclei
• neutron rich: more than usual neutrons
• neutronization: an electron and proton combining to form a neutron
• neutrons from carbon-13: process by which neutrons are freed in the s process
• nuclear statistical equilibrium: equilibrium of nuclei emitting and absorbing particles
• nucleon: proton or neutron
• nuclide: atomic nucleus associated with a specific isotope
• oscillator strength: fraction expressing QM's contribution to the probability of absorption
• oxygen burning: fusion reaction starting with oxygen
• p-process: synthesis of elements through proton capture
• photodisintegration: breakdown of a nucleus by a gamma ray
• quantum field theory: reworking of quantum mechanics incorporating fields
• quantum mechanics: modern mechanical theory of small things, on the scale of atoms
• r-process: synthesis of elements through neutron capture faster than beta decay
• radioactive decay: changes in atomic nuclei that happen over time
• rp-process: synthesis of elements through repeated proton capture
• s-process: synthesis of elements through neutron capture and beta decay
• silicon burning: alpha process fusion starting at silicon
• state of excitation: energy level of something above the minimum
• state of ionization: difference in an ion's electron count versus proton count
• trans-iron element: elements with atomic number greater than that of iron
• triple alpha process: fusion reaction chain turning helium-4 into carbon
• valley of beta stability: set of isotopes not prone to beta decay
• Z+: symbol for ion or ion charge
• ATST (DKIST): 4 m solar telescope at Haleakala Observatory
• attenuation coefficient (opacity): a measure of opaqueness of a material
  • absorption coefficient: measure of how much light a substance absorbs
• AU (astronomical unit): about 93 million miles
• AU Mic (AU Microscopii): nearby star with disk and planets
• AU Microscopii: nearby star with disk and planets
• AUASS (Arab Union for Astronomy and Space Sciences): has hosted conferences
• Auger de-excitation: see Auger effect
• Auger effect: atom's emission of an electron along with a photon
• Auger Observatory (Pierre Auger Observatory): cosmic-ray observatory in Argentina
• AURA (Association of Universities for Research in Astronomy): collaboration of universities operating observatories
  • Gemini Observatory: pair of telescopes in Hawaii and Chile
• aurora: light produced by atmosphere and solar wind
  • solar particle event: episode of higher velocity solar wind
• aurora australis: see aurora
• aurora borealis: see aurora
• Australia
• Anglo-Australian Telescope: 3.9-m reflector telescope in Australia
• ANU 2.3m Telescope: 2.3-m telescope at Siding Spring Observatory
• Australia Telescope Compact Array: radio telescope in eastern Australia
• Australian Square Kilometre Array Pathfinder: radio telescope array of 36 12-meter dishes
• Automated Patrol Telescope: 0.5 m telescope at Siding Spring Observatory
• Badgerys Creek Interferometer 101-MHz Survey: early 1950s survey of southern-hemisphere radio sources
• CANGAROO: Collaboration between Australia and Nippon for a Gamma Ray Observatory in the Outback
• GOTO: telescope array to follow up gravitational wave signals
• Long Baseline Array: radio interferometer using Australian telescopes
• Lupus Transit Survey: survey for hot Jupiters in a region of constellation Lupus
• MACHO Project: survey searching out microlensing that could indicate a MACHO
• Mopra Telescope: Australian 22 m radio telescope
• MOST­: radio telescope in New South Wales
• Murchison Widefield Array: low frequency radio telescope
• Narrabri Stellar Intensity Interferometer: 1960s optical interferometer for measuring stellar diameters
• Parkes Observatory: Australian observatory with large single-dish radio telescope
• Parkes Pulsar Timing Array: group of pulsars timed by Parkes Observatory
• Research School of Astronomy and Astrophysics: Australian National University astrophysics school
• Siding Spring Observatory: observatory in New South Wales, Australia
• SkyMapper: automated 1.35 m optical telescope in Australia
• Square Kilometre Array: planned radio telescope with square-kilometer collecting area
• SUSI: optical interferometer in Australia
• TAIPAN: multi-object spectrograph with robot fiber-positioner
• UK Schmidt Telescope: 1.2 meter telescope in Australia with wide field-of-view
• UTMOST: telescope aiming to detect radio transients
• Australia Telescope: see Australia Telescope Compact Array
• Australia Telescope: see Long Baseline Array
• Australia Telescope Compact Array: radio telescope in eastern Australia
  • Australia Telescope Large Area Survey: radio survey of two survey fields
  • Long Baseline Array: radio interferometer using Australian telescopes
• Australia Telescope Large Area Survey: radio survey of two survey fields
• Australia Telescope Long Baseline Array (Long Baseline Array): radio interferometer using Australian telescopes
• Australia Telescope National Facility
• ATNF Pulsar Catalogue: online catalog of pulsars
• Australian
• Millimeter Astronomy Legacy Team: Australian initiative producing millimeter surveys
• Australian Astronomical Observatory
• UK Schmidt Telescope: 1.2 meter telescope in Australia with wide field-of-view
• Australian Long Baseline Array (Long Baseline Array): radio interferometer using Australian telescopes
• Australian National University
• Siding Spring Observatory: observatory in New South Wales, Australia
• Australian Square Kilometre Array Pathfinder: radio telescope array of 36 12-meter dishes
• autoconversion rate: rate at which water changes from cloud droplets to new raindrops
• automated
• APASS: down to 16 magnitude
• Automated Planet Finder: robotic telescope to find exoplanets using RV method
• Evryscope: automated array of telescopes to uncover transients
• HATNet: distributed array of telescopes to search for transients
• Infrared Telescope Maffei: 80 cm infrared telescope in Antarctica
• KELT: pair of telescopes that searched for transients
• Livermore Optical Transient Imaging System: automated telescope aiming to catch GRB optical counterparts
• MASCARA: distributed array of telescopes to search for exoplanets
• MASTER Robotic Net: network of automated telescopes to identify transients
• MEarth Project: automated observatories monitoring nearby red dwarfs for transits
• NGTS: survey of transits from Chile
• Palomar 48 Inch Telescope: 48 inch Schmidt telescope at Palomar Observatory
• Palomar 60-inch Telescope: 60 inch telescope at Palomar Observatory
• Palomar Transient Factory: survey designed to find transients
• Pi of the Sky: survey aimed at finding gamma-ray-burst visual counterparts
• pipeline: set series of tasks to perform on something
• Qatar Exoplanet Survey: photometric survey that searched for transiting planets
• 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 1.35 m optical telescope in Australia
• SPECULOOS: search for Earth-like exoplanets orbiting nearby dim stars
• TAROT: network of telescopes to catch GRB optical counterparts
• Tokyo Photoelectric Meridian Circle: Japanese telescope to determine the position of stars and planets
• Trans-Atlantic Exoplanet Survey: 2000s exoplanet-search survey using three telescopes
• TRAPPIST: a ground-based automated transiting-planet finding telescope
• Zwicky Transient Facility: survey designed to find transients
• Automated Lunar and Meteor Observatory: ground observatory in Alabama to record Moon-meteoroid impacts
• Automated Patrol Telescope: 0.5 m telescope at Siding Spring Observatory
• Automated Planet Finder: robotic telescope to find exoplanets using RV method
  • Lick Observatory: California observatory of long standing
• Automatic Plate Measuring Machine
• APM Galaxy Survey: 1990s survey of galaxies in southern sky
• Large Bright QSO Survey: 1980s quasar survey
• automatic plate measuring machine (plate measuring machine): machine to measure position of images on photographic plates
• Autonomous Space Transport Robotic Operations: experiment re robotic satellite servicing/refueling in space
• autumnal equinox: see equinox
• avalanche photodiode: see Geiger-avalanche photodiode
• AVMR: see velocity-metallicity relation
  • age-metallicity relation: older stars generally have lower metallicity
  • age-velocity-dispersion relation: relation between stellar age and peculiar velocity
• Avogadro constant (Avogadro's number): number of hydrogen atoms per gram
  • Boltzmann constant: relates particle energy and temperature
• Avogadro's number: number of hydrogen atoms per gram
• Avogadro's number: see mole
  • ideal gas law: relates pressure, temperature, and volume
• AVR (age-velocity-dispersion relation): relation between stellar age and peculiar velocity
• AW (Alfvén wave): a type of transverse wave along magnetic field lines in plasma
• award
• Special Breakthrough Prize: Breakthrough Prize award in addition to the year's annual awards
• AWCA (American Workshop on Cometary Astronomy): renamed to be international, i.e., IWCA
• AWM: see rare designator prefixes
• AWSoM: see SWMF
• AX: see ASCA
• AXAF (Chandra X-ray Observatory): space X-ray telescope
• axial precession: see precession
  • equatorial coordinate system: latitude/longitude-like system for the celestial sphere
  • precession of the equinoxes: Earth axial precession with a 26000-year cycle
• axial tilt (obliquity): angle between an object's rotational and orbital axes
• axiom
• cosmological principle: on a large scale the universe is the same everywhere
• axion: proposed light, electrically neutral elementary particle
  • dark matter: matter in galaxies and galaxy clusters suggested by their gravity
  • exotic star: term for theoretical stars not made of atoms/ions
• Axion Dark Matter Experiment: a search for axions as potential dark matter particles
• axion-like particle: see axion
• AXIS: concept for space X-ray observatory
• Axis of Evil: suspicious alignment of CMB anisotropies
• axisymmetric: identical in any direction from an axis
• axisymmetric galaxy
• galaxy: gravitationally-bound group of stars
• AXP (anomalous X-ray pulsar): X-ray pulsars with no high-mass companion
  • magnetar: neutron star with a strong magnetic field
• AXS: see ASCA
• az/el system (horizontal coordinate system): celestial coordinate system based upon horizon and north
• azane (ammonia): particular compound of nitrogen and hydrogen
• azimuth: see horizontal coordinate system
  • altazimuth mount: simple two-axis telescope mount
• azimuth-elevation mount (altazimuth mount): simple two-axis telescope mount
• azimuthal number: see spherical harmonics
• azimuthal quantum number: see electron orbital
• AzTEC: see Atacama Submillimeter Telescope Experiment
• AzTEC: see James Clerk Maxwell Telescope
• AzTEC: see Large Millimeter Telescope
• AzTEC: see rare designator prefixes
  • AzTEC-3: very distant starburst galaxy
• AzTEC J100020.54+023509.3 (AzTEC-3): very distant starburst galaxy
• AzTEC-3: very distant starburst galaxy
• AzV (Catalog of Azzopardi & Vigneau): probable stars in the SMC