Term Index (J)

 J0  J1  J2  JA  JB  JC  JD  JE  JF  JG  JH  JI  JK  JL  JO  JP  JS  JU  JV  JW  JY

• J (J band): atmospheric window centered around 2.2 microns, or 136 THz
• J (joule): SI unit of energy
• J (specific angular momentum): absolute angular momentum divided by mass
• J: see J designator
• J: see double star designation
  • Two Micron All-sky Survey: near-infrared survey of both hemispheres
  • UVJ diagram: diagram to identify star formation in distant galaxies
• j (emission coefficient): measure of how much light a substance emits
• J band: atmospheric window centered around 2.2 microns, or 136 THz
  • Gattini-IR: IR transient survey telescope
  • infrared: light with wavelength too long for our eyes to sense
• J coefficients: see J₂
• J designator: designator using equatorial coordinates at year 2000
• J-MAG: see JUICE
• J-region: see J-region asymptotic giant branch
• J-region AGB (J-region asymptotic giant branch): standard candle consisting of selected AGB stars
• J-region asymptotic giant branch: standard candle consisting of selected AGB stars
• J-type shock: see shock wave
• J0651 (WD J0651+2844): binary pair of closely-orbiting white dwarfs
• J1407: star eclipsed by a body with a ring system
• J1407b: see J1407
• J1713+0747: binary system with millisecond pulsar and white dwarf
• J2
• gravitational potential model: mathematical model of an astronomical body's gravitational field
• J2 perturbation: see J₂
• J2000 (epoch J2000.0): noon 1/1/2000 GMT as used as a time reference
• J2000 epoch: see epoch
• J2000 equinox
• equinox: point-in-time when tilt of Earth is neither toward nor away from the Sun
• J2000.0 (epoch J2000.0): noon 1/1/2000 GMT as used as a time reference
  • Terrestrial Time: current measure of time for astronomical observations on Earth
• J2000.0 epoch: see epoch
• J2000.0 equinox: equinox as of the J2000.0 epoch used as a positional reference
  • equinox: point-in-time when tilt of Earth is neither toward nor away from the Sun
• J20000 epoch: see epoch
• J200322.54-114203.3 (SMSS J2003-1142): unusual giant star in Milky Way halo
• J₂: geopotential coefficient regarding a planet's oblateness
• J₃: see J₂
• JAAVSO: see American Association of Variable Star Observers
• JAC (Joint Astronomy Centre): operated two UK telescopes in Hawaii
• Jacob's staff (cross-staff): historical device for measuring angular distances
• Jacobi constant: see Jacobi integral
• Jacobi integral: method of solving some three-body problems
• Jacobus Kapteyn Telescope: see Isaac Newton Group of Telescopes
• Jacobus Kapteyn Telescope: see Roque de los Muchachos Observatory
• Jacoby: see rare designator prefixes
• JADE: see Juno
• JADES: see James Webb Space Telescope
• JaFu: see rare designator prefixes
• JAGB (J-region asymptotic giant branch): standard candle consisting of selected AGB stars
• JAGUAR (JWST Extragalactic Mock Catalog): mock catalog of distant infrared galaxies
• JAM (Jeans anisotropic modeling): method of determining stellar kinematics of early type galaxies
• James Clerk Maxwell Telescope: far-infrared telescope in Hawaii
  • East Asian Observatory: operator of JCMT
• James Webb Space Telescope: 6.5-meter infrared space telescope at L2
  • aperture masking interferometry: interferometry by means of a single telescope with a mask
  • CSA: includes astronomical research
  • NIRCam: near infrared imager on JWST
  • NIRSpec: near infrared spectrograph on JWST
• Jansky
• Very Large Array: radio telescope in New Mexico
• jansky: unit of measurement of spectral flux density
• JANUS: see JUICE
• Janus: see shepherd moon
• Japan
• Bisei Asteroid Tracking Telescope for Rapid Survey: Japanese telescope surveying to find NEOs and space junk
• DECIGO: proposed Japanese space mission to detect gravitational waves
• Fugaku: Japanese petaflop/exaflop supercomputer
• Institute of Space and Astronautical Science: Japanese national research organization
• Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• Japan Spaceguard Association: Japanese telescope tracking NEOs and space junk
• KAGRA: gravitational wave detector in Japan preparing for operation
• Kamioka Observatory: Japanese underground particle detector
• MISAO project: search for variable stars and transients
• Mu Space Engineering Spacecraft: series of Japanese astronomy space missions
• National Astronomical Observatory of Japan: Japanese astronomy organization
• Okayama Astrophysical Observatory: observatory at Mt. Chikurinji
• Publications of the Astronomical Society of Japan: bimonthly journal
• TAMA 300: small prototype gravitational wave detector in Japan
• Tokyo Photoelectric Meridian Circle: Japanese telescope to determine the position of stars and planets
• Variable Star Observers League in Japan: amateur variable star group
• VERA: VLBI project to map the Milky Way
• Japan Aerospace Exploration Agency: Japan agency includes astronomical research
• Japan Amateur Photoelectric Observers Association: past amateur astronomy collaboration
• Japan Spaceguard Association: Japanese telescope tracking NEOs and space junk
• Japanese
• Kiso Survey of Ultraviolet Excess Galaxies: 1980 Japanese survey
• WINERED: near-infrared non-cryogenic spectrograph
• JAPOA (Japan Amateur Photoelectric Observers Association): past amateur astronomy collaboration
• JAVSO: see American Association of Variable Star Observers
• JAXA (Japan Aerospace Exploration Agency): Japan agency includes astronomical research
  • AKARI: Japanese space infrared telescope
  • ASCA: 1990s Japanese space X-ray telescope
  • BepiColombo: mission to Mercury
  • Ginga: 1980s Japanese space X-ray telescope
  • HALCA: Japanese space radio telescope operating 1997-2005
  • Hayabusa2: JAXA mission that returned a sample of an asteroid
  • Hisaki: retired Japanese space ultraviolet telescope
  • Hitomi: 2016 Japanese space X-ray telescope
  • Institute of Space and Astronautical Science: Japanese national research organization
  • IRTS: 15-cm infrared telescope on Japanese satellite
  • LiteBIRD: planned spacecraft to map CMB polarization
  • MAXI: Japanese X-ray camera on the International Space Station
  • MMX: Japanese probe to bring back a sample of a Martian moon
  • SELENE: 2007-2008 Japanese lunar probe
  • SPICA: plan for a future space IR telescope
  • Suzaku: space X-ray telescope
  • XRISM: X-ray space telescope launched in 2023
  • Yohkoh: 1990s Japanese solar observatory spacecraft
• JBO (Jodrell Bank Observatory): radio observatory in England
  • Mark II: 38 m radio telescope in England
  • MERLIN: VLBI array spread across England
• JC: see double star designation
• JCM: see Juno
• JCMT (James Clerk Maxwell Telescope): far-infrared telescope in Hawaii
  • AMUSE²: survey of ELANs
  • East Asian Observatory: operator of JCMT
  • Mauna Kea: Hawaiian mountain, the site of observatories
  • Mauna Kea Observatories: observatories on Mauna Kea in Hawaii
• JCMT dust and gas In Nearby Galaxies Legacy Exploration (JINGLE): survey of dust and gas in galaxies
• JD (Julian date): time in days since noon UT November 24 4714 BC Gregorian
• JDEM
• Roman Space Telescope: proposed near-infrared space observatory
• JDN: see Julian date
• Jeans anisotropic MGE (Jeans anisotropic modeling): method of determining stellar kinematics of early type galaxies
• Jeans anisotropic modeling: method of determining stellar kinematics of early type galaxies
• Jeans anisotropic multi-Gaussian expansion (Jeans anisotropic modeling): method of determining stellar kinematics of early type galaxies
• Jeans criterion: see Jeans length
• Jeans density: see Jeans length
• Jeans equations: relating the motion of stars to the surrounding gravitational field
• Jeans escape: type of ongoing escape of gas particles from atmosphere
  • atmospheric escape: escape of gas particles from a planet's atmosphere
  • hydrodynamic escape: escape of gas particles from atmosphere due to heating
  • Jeans parameter: ratio measuring a tendency of an atmosphere to escape
• Jeans escape parameter (Jeans parameter): ratio measuring a tendency of an atmosphere to escape
• Jeans instability: see Jeans length
• Jeans length: critical radius above which gravity will collapse a cloud
• Jeans mass: see Jeans length
• Jeans modeling: see Jeans equations
• Jeans parameter: ratio measuring a tendency of an atmosphere to escape
• Jeans swindle: see Jeans length
• JEDI: see Juno
• JEF: see double star designation
• jellyfish galaxy: galaxy with a gas tail including star formation
• JEM-X: see INTEGRAL
• jet: stream of matter from an astronomical body
• jet (jet stream): upper-atmosphere narrow west-to-east streams of air
  • 3C 273: first quasar discovered
  • 3C 279: striking variable quasar
  • 3C 303: Seyfert galaxy of interest
  • 3C 348: giant elliptical radio galaxy
  • 3C 9: first quasar discovered
  • Centaurus A: nearby radio galaxy
  • Cygnus A: early-discovered radio galaxy showing a quasar
  • M87: supergiant elliptical galaxy in local universe
  • superrotating wind: wind traveling in the same direction as the planet is rotating
  • TXS 0506+056: blazar that is a neutrino source
  • zonal flow: east-west air circulation
  • zone: apparent "horizontal" band in an atmosphere
• jet current: electric current within a plasma jet
• Jet Propulsion Laboratory: NASA technology research center
• jet stream: upper-atmosphere narrow west-to-east streams of air
• jet stream: see jet
  • superrotating wind: wind traveling in the same direction as the planet is rotating
  • thermal wind: type of wind due to temperature gradients that vary by altitude
  • zonal flow: east-west air circulation
  • zone: apparent "horizontal" band in an atmosphere
• JET-X (Joint European Telescope for X-ray astronomy): 1990s X-ray space observatory never launched
• JET-X: see Spektr-RG
• jets
• bipolar outflow: streams of matter from the poles of a protostar
• Blandford-Payne mechanism: means of by which an accretion disk can power a jet
• Herbig-Haro object: type of glowing nebula near protostars
• jet current: electric current within a plasma jet
• mass loading: moving gas gaining mass from clouds or stars
• microquasar: stellar-sized black hole with quasar-like activity
• quasar: distant, bright object that appears something like a star
• relativistic beaming: directional relativistic effect on light from relativistic speeds
• Jezero Crater: Perseverance rover landing site on Mars
• JFC: see long-period comet
• JGR (Journal of Geophysical Research): American Geophysics Union peer-reviewed research journal
• Jhelum stream
• Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams
• JHK (JHK photometric system): system to classify stars according to near-infrared colors
• JHK photometric system: system to classify stars according to near-infrared colors
• JILA: U Colorado/NIST research organization
• JINGLE: survey of dust and gas in galaxies
• JIRAM: see Juno
• JIVE (Joint Institute for VLBI ERIC): central EVN facility
• JKT: see Isaac Newton Group of Telescopes
• JKT: see Roque de los Muchachos Observatory
• JL: see rare designator prefixes
• Jodrell Bank Experimental Station (Jodrell Bank Observatory): radio observatory in England
• Jodrell Bank Mark II (Mark II): 38 m radio telescope in England
• Jodrell Bank Observatory: radio observatory in England
  • Mark II: 38 m radio telescope in England
  • MERLIN: VLBI array spread across England
• Johannsen-Psaltis metric: metric template allowing metrics to be written as a general expansion
  • theoretical modified GR metric: metric devised to define modifications to GR
• Johannsen-Psaltis spacetime: see Johannsen-Psaltis metric
• John A. Galt Telescope
• Dominion Observatory 1420 MHz Source Catalog: 1960s survey of northern-hemisphere radio sources
• Dominion Radio Astrophysical Observatory: radio observatory in British Columbia, Canada
• Johns Hopkins University
• Space Telescope Science Institute: science operator of space telescopes
• Johnson System (UBV photometric system): commonly-cited photometric system for describing stars' colors
• Johnson system (Vega system): magnitude calibration such that Vega has zero magnitude
• Johnson-Cousins system: see UBV photometric system
  • I band: passband for near-infrared light
• Johnson-Morgan System (UBV photometric system): commonly-cited photometric system for describing stars' colors
• Johnson-Nyquist noise (thermal noise): noise inherent in electronic component warmer than absolute zero
• JOI: see Juno
• Joint Astronomy Centre: operated two UK telescopes in Hawaii
• Joint Dark Energy Mission
• Roman Space Telescope: proposed near-infrared space observatory
• Joint European Telescope for X-ray astronomy: 1990s X-ray space observatory never launched
• Joint Institute for Laboratory Astrophysics (JILA): U Colorado/NIST research organization
• Joint Institute for VLBI ERIC: central EVN facility
• Joint Institute for VLBI in Europe (Joint Institute for VLBI ERIC): central EVN facility
• joint probability distribution (mixture): type of probability distribution resulting from two others
• Jonckhèere: see rare designator prefixes
• joule: SI unit of energy
  • energy: physical state needed to do something
• Joule heating (Ohmic heating): heating resulting from an electric current through a material
• journal
• Publications of the Astronomical Society of Japan: bimonthly journal
• Publications of the Astronomical Society of the Pacific: monthly journal
• Journal of Geophysical Research: American Geophysics Union peer-reviewed research journal
• Journal of the American Association of Variable Star Observers: see American Association of Variable Star Observers
• Jovian planet (giant planet): planet of more than 10 Earth masses
• JOY: see double star designation
• JP metric (Johannsen-Psaltis metric): metric template allowing metrics to be written as a general expansion
  • theoretical modified GR metric: metric devised to define modifications to GR
• JP spacetime: see Johannsen-Psaltis metric
• JPA: see Giotto
• JPL (Jet Propulsion Laboratory): NASA technology research center
  • Galaxy Evolution Explorer: observatory-satellite with 50-cm ultraviolet telescope
  • Table Mountain Observatory: NASA observatory near Los Angeles
• JSGA (Japan Spaceguard Association): Japanese telescope tracking NEOs and space junk
• JSP: see double star designation
• Juchert: see rare designator prefixes
• JUICE: mission to Jupiter in development
• Julian calendar: calendar of 365 days and a leap day once every four years
• Julian date: time in days since noon UT November 24 4714 BC Gregorian
  • Julian calendar: calendar of 365 days and a leap day once every four years
• Julian day (Julian date): time in days since noon UT November 24 4714 BC Gregorian
• Julian day number: see Julian date
• Julian year: see Julian calendar
  • Julian date: time in days since noon UT November 24 4714 BC Gregorian
  • sidereal: relative to the fixed position of the stars
• Juno: mission to Jupiter
• Juno: see asteroid
  • gravity sounding: measuring a planet's gravitation field by study of nearby probe flights
  • Io: well-known Jupiter moon
• Juno Orbit Insertion: see Juno
• JunoCam: see Juno
• Jupiter: largest planet in the solar system
  • Callisto: well-known Jupiter moon
  • Comet Shoemaker-Levy 9: comet that collided with Jupiter in 1994
  • Europa: well-known Jupiter moon
  • Europa Clipper: NASA Europa space probe launched in 2024
  • Europa Lander: plan for a late 2020s Europa probe landing on the surface
  • Galileo: circa 1990s space mission to Jupiter
  • Ganymede: well-known Jupiter moon
  • grand tack hypothesis: solar system formation model with Jupiter and Saturn migrating
  • helium rain: possible source of heat in giant planet atmospheres
  • Io: well-known Jupiter moon
  • JUICE: mission to Jupiter in development
  • Juno: mission to Jupiter
  • liquid planet: planet consisting of liquid
  • ring system: disk or set of rings orbiting a planet
  • shepherd moon: small moon affecting outer edge of a planet's ring
  • solar system object: the Sun, solar system planets, minor planets, comets, and moons
  • Voyager: space probes to observe planets and the edge of the solar system
• Jupiter I (Io): well-known Jupiter moon
• Jupiter Icy Moons Explorer (JUICE): mission to Jupiter in development
• Jupiter II (Europa): well-known Jupiter moon
• Jupiter III (Ganymede): well-known Jupiter moon
• Jupiter IV (Callisto): well-known Jupiter moon
• Jupiter mass: see mass
  • solar mass: mass unit representing the mass of the Sun
• Jupiter Orbiter Probe (Galileo): circa 1990s space mission to Jupiter
• Jupiter Trojan: see asteroid belt
• Jupiter-family comet: see long-period comet
• Jupiters: see extra-solar planet
• Jupyter: notebook-style programming interface used with Python
• JVAS: see rare designator prefixes
• JVLA (Very Large Array): radio telescope in New Mexico
• JW: see rare designator prefixes
• JWST (James Webb Space Telescope): 6.5-meter infrared space telescope at L2
  • aperture masking interferometry: interferometry by means of a single telescope with a mask
  • CEERS: JWST early release observation program covering the EGS
  • CSA: includes astronomical research
  • grism: combination of a grating and a prism
  • JWST ETC: Python-based exposure time calculator for JWST
  • NIRCam: near infrared imager on JWST
  • NIRSpec: near infrared spectrograph on JWST
  • Ultimate Spitzer Phase Curve Survey: investigation of exoplanet atmospheres
• JWST Advanced Deep Extragalactic Survey: see James Webb Space Telescope
• JWST ETC: Python-based exposure time calculator for JWST
• JWST exposure time calculator (JWST ETC): Python-based exposure time calculator for JWST
• JWST Extragalactic Mock Catalog: mock catalog of distant infrared galaxies
• Jy (jansky): unit of measurement of spectral flux density