Term Index (I)

Astrophysics (Index)

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Term Index (I)

Astrophysical terms and names of things beginning with the letter I.

I2 IA IB IC ID IE IF IG IH II IK IL IM IN IO IP IQ IR IS IT IU IV IW IX

I (I band): passband for near-infrared light
I: see IRAS
I: see Stokes parameters
I: see double star designation
I: see state of ionization
- HI region: cloud of neutral atomic hydrogen
- spectral line: dark or bright line in a spectrum
i: see griz photometric system
i: see ugriz photometric system
I band: passband for near-infrared light
I Zw: see Catalog of Galaxies and Clusters of Galaxies
I Zw 18 (I Zwicky 18): blue compact galaxy with low metallicity
I Zw 36 (Haro 29): a blue compact galaxy
I Zwicky 18: blue compact galaxy with low metallicity
i': see ugriz photometric system
i-band: see Hubble Ultra-Deep Field
I2C: see GI2T
- optical interferometer: interferometer of visible light
I2T: see GI2T
- optical interferometer: interferometer of visible light
IAA (Academia Sinica Institute of Astronomy and Astrophysics): Taiwanese astrophysics research organization
IAC (Instituto de Astrofísica de Canarias): research institute on Canary Islands
IACT (imaging atmospheric Cherenkov telescope): gamma-ray imager based on atmospheric Cherenkov radiation
- Cherenkov detector: type of high energy photon or particle detector
Iapetus: see Saturn
- moon: a planet's natural satellite, such as Earth's
IAPPP (International Amateur-Professional Photoelectric Photometry): organization active 1980-2000+
IAPS (Istituto di Astrofisica e Planetologia Spaziali): Italian astrophysical research institute within INAF
IAS (Institute for Advanced Study): research institution
IAS (Istituto di Astrofisica Spaziale): former name of Italian astrophysics research institution
IASY (International Active Sun Years): 1969-1971 initiative for solar surveys
IAU (International Astronomical Union): association of professional astronomers
- Committee for Small-Body Nomenclature: early 2000s IAU division since replaced by WG-SBN
- dwarf planet: round like a planet, only smaller
- FITS: IAU standard for data such as images
- galactic coordinate system: celestial coordinate system system based upon the galactic plane
- IAU symposium: IAU-sponsored science symposiums
- Minor Planet Center: organization collecting and organizing minor planet data
- Small Bodies Names Committee: old name of IAU Committee for Small Body Nomenclature
- Working Group for Planetary System Nomenclature: IAU group on terminology regarding planetary systems
IAU Circular: see Central Bureau for Astronomical Telegrams
IAU Circular: see International Astronomical Union
IAU galactic coordinate system (galactic coordinate system): celestial coordinate system system based upon the galactic plane
IAU symposium: IAU-sponsored science symposiums
IAUC: see Central Bureau for Astronomical Telegrams
IAUC: see International Astronomical Union
IAUS (IAU symposium): IAU-sponsored science symposiums
IAYC (International Astronomical Youth Camp): summer camp
IBAS: see INTEGRAL
IBEX (Interstellar Boundary Explorer): satellite observing the ISM/heliosphere boundary
IBEX-Hi: see Interstellar Boundary Explorer
IBEX-Low: see Interstellar Boundary Explorer
IBIS: see INTEGRAL
IBVS (Information Bulletin on Variable Stars): former 1961-2019 publication on variable stars
IC (Index Catalog): 1895 catalog of galaxies, star clusters, and other nebulae
IC (Intracluster): region between objects of a cluster such as between stars in a star cluster
IC 1340: see Cygnus Loop
IC 342: spiral galaxy in the Council of Giants
- Council of Giants: twelve large galaxies surrounding the Local Group
IC 342/Maffei Group: see IC 342
ICAT (Canadian Institute for Theoretical Astrophysics): national research organization at University of Toronto
ICC: see InSight
ICE (International Cometary Explorer): 1980s space mission flying by comets
ice: solid state of water
- ice giant: planet denser than gas planets and less than rocky planets
- snow line: distance from protostar so cool that water condenses
- superionic ice: odd state of water at high temperature and pressure
- water-ice planet: planet made entirely of water ice
ice dwarf (plutoid): Pluto-like dwarf planet
ice giant: planet denser than gas planets and less than rocky planets
- gas giant: large planet made largely of gas
- giant planet: planet of more than 10 Earth masses
ice line (snow line): distance from protostar so cool that water condenses
- ice: solid state of water
ice transition radius: see snow line
IceCube: neutrino detector at the South Pole
- South Pole Station: science station at the South Pole
IceCube Neutrino Observatory (IceCube): neutrino detector at the South Pole
IceCube-Gen2: see IceCube
ICF (ionization correction factor): relations between ion abundances and element abundances
ICM (intracluster medium): hot plasma throughout a galaxy cluster
- intergalactic medium: matter between galaxies
ICQ (International Comet Quarterly): journal regarding comets
ICRC (International Cosmic Ray Conference): bi-annual cosmic ray conference since 1947
ICRF: celestial reference frame based upon quasars
- celestial reference frame: frame of reference associated with a catalog of stars or quasars
- International Celestial Reference System: standardized variation of equatorial coordinate system
ICRF1: see ICRF
- celestial reference frame: frame of reference associated with a catalog of stars or quasars
ICRF2: see ICRF
- celestial reference frame: frame of reference associated with a catalog of stars or quasars
ICRF3: see ICRF
- celestial reference frame: frame of reference associated with a catalog of stars or quasars
- International Celestial Reference System: standardized variation of equatorial coordinate system
ICRS (International Celestial Reference System): standardized variation of equatorial coordinate system
- celestial coordinate system: system for specifying position of celestial objects
- Gaia Celestial Reference Frame: celestial reference frame based upon Gaia data
- Hipparcos Celestial Reference Frame: astronomical reference frame based upon Hipparcos catalog
- ICRF: celestial reference frame based upon quasars
IDA (International Dark-Sky Association): organization promoting control of light pollution
IDA: see InSight
IDC: see InSight
ideal gas: see ideal gas law
- Hayashi limit: limit on the temperature of a star dependent upon its mass and luminosity
- Lane-Emden equation: form of equation of state for gas ball in hydrostatic equilibrium
ideal gas law: relates pressure, temperature, and volume
- electron degeneracy: electrons set free of atoms by the Pauli exclusion principle
- Hayashi limit: limit on the temperature of a star dependent upon its mass and luminosity
- isothermal core: core region of a body of all the same temperature
- statistical mechanics: mechanical behavior based upon probability
IDEX: see IMAP
IDFT: see fast Fourier transform
IDL: interactive vector-oriented programming language
IDP: see interplanetary medium
IDS: see Isaac Newton Telescope
IDS: see Shane Telescope
IDS: see Washington Double Star Catalog
IDV: see variable star
IEEE (Institute of Electrical and Electronics Engineers): professional engineering association
- ITU: international body coordinating communications technology
IEO: see near-Earth object
IERS (International Earth Rotation and Reference Systems Service): service monitoring Earth's rotation and precession
IfA (Institute for Astronomy): U Hawaii astronomy research organization
IFN (integrated flux nebula): fuzzy illuminated nebula within Milky Way halo
IFS: see European Southern Observatory Very Large Telescope
IFS: see SPHERE
IFS: see integral field spectrograph
IFTS (imaging Fourier transform spectroscopy): Michelson-interferometer-based imaging spectroscopy
IFU (integral field unit): instrument to allow a spectrograph to capture data over a 2D field
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
IFU Observation

Sloan Digital Sky Survey: imaging survey of 500,000,000 objects in 35% of sky

IFU observation: see integral field unit
IFU spectroscopy: see integral field unit
IGAPS: see IPHAS
IGAS: see Ulysses
IGM (intergalactic medium): matter between galaxies
- intracluster medium: hot plasma throughout a galaxy cluster
IGR: see INTEGRAL
IGRINS: see Gemini Observatory
IGRINS-2: see Gemini Observatory
IGVV: see Catalogue of Interacting Galaxies
IGW (internal gravity wave): ripples in a change in density in a fluid
IGY (International Geophysical Year): 1957-1958 initiative for geophysical and related astronomical research
IHW (International Halley Watch): initiative to coordinate observation of Halley's Comet in 1986
II: see state of ionization
- spectral line: dark or bright line in a spectrum
II Zw: see Catalog of Galaxies and Clusters of Galaxies
III: see state of ionization
- spectral line: dark or bright line in a spectrum
III Zw: see Catalog of Galaxies and Clusters of Galaxies
IKT: see rare designator prefixes
illumination: measure of light energy producing a telescope's image
Illustris Project: 2013-2015 series of cosmological simulations
IllustrisTNG Project: see Illustris Project
ILMT (International Liquid Mirror Telescope): 4-meter liquid mirror telescope under construction in India
iLocator: see Large Binocular Telescope
ILOM (In-situ Lunar Orientation Measurement): planned experiment to monitor lunar rotation via astrometry from the Moon
ILOT (intermediate luminosity optical transient): visible-light transient a bit brighter than a nova
ILR: see Lindblad resonance
IM (intensity mapping): measure of cosmic matter density
IM Lup

MAPS: ALMA survey researching planet-formation

IM Nor: see T Pyxidis
- T Coronae Borealis: recurrent nova expected to erupt sometime within 2024-2026
IM Normae: see T Pyxidis
- T Coronae Borealis: recurrent nova expected to erupt sometime within 2024-2026
IMACS: see Magellan Telescopes
- PRIMUS: spectrographic survey of galaxies out to redshift 1
image dissector: see photomultiplier tube
image dissector photomultiplier: see photomultiplier tube
image plane (focal plane): plane within optical system at which an image is in focus
image processing

convolutional neural network: type of image processing software
Fourier space: domain into which the Fourier transform maps a function
GPU: type of CPU tailored to handling computer graphics
Hough transform: algorithm used in image processing
top hat filter: type of image processing mechanism to make small objects stand out
U-Net: neural network software for image reconstruction

Image Reduction and Analysis Facility: NOAO-developed image manipulation/viewing software
image scale (plate scale): relation between angle and distance across an image
image slicer: see integral field spectrograph
image slicer: see integral field unit
image stabilization: camera mechanism to compensate for movement
- shift-and-add: common speckle-suppression technique
image stacking (stacking): combining images of the same object
IMAGE: satellite mission to study magnetosphere
Image-Dissector Scanner: see Shane Telescope
imager: essentially a word for camera, produces 2D image over some bandwidth
- eROSITA: Russian/German space X-ray telescope launched in 2019
- Gemini Planet Imager: infrared instrument to overcome signal noise imaging exoplanets
- Keck Planet Imager and Characterizer: extreme AO upgrade under development for Keck
- SPHERE: VLT instrument for imaging exoplanets
Imager for Magnetopause-to-Aurora Global Exploration (IMAGE): satellite mission to study magnetosphere
imaginary number: see complex number
imaginary part: see complex number
imaginary unit: see complex number
imaging

synthetic aperture radar: method of using moving radar with a stationary target
Zeeman-Doppler imaging: technique for imaging stellar magnetic fields

imaging atmospheric Cherenkov telescope: gamma-ray imager based on atmospheric Cherenkov radiation
- Cherenkov detector: type of high energy photon or particle detector
imaging Fourier transform spectrometer: see imaging Fourier transform spectroscopy
imaging Fourier transform spectroscopy: Michelson-interferometer-based imaging spectroscopy
imaging spectrograph (imaging spectrometer): device to capture spectrum point-by-point of an image
imaging spectrometer: device to capture spectrum point-by-point of an image
- spectroscopy: measurement of light with various electromagnetic wavelengths
Imaging X-ray Polarimetry Explorer (IXPE): space observatory with X-ray polarimeters
IMAP: future solar science probe
IMAP-Hi: see IMAP
IMAP-Lo: see IMAP
IMAP-Ultra: see IMAP
IMAPS (Interstellar Medium Absorption Profile Spectrograph): 1980s/1990s UV spectrometer
IMaX: see SUNRISE
IMB: 1980s neutrino detector
IMBH (intermediate-mass black hole): black hole between stellar mass and supermassive
- black hole: region of such high mass that light cannot escape
- ultraluminous X-ray source: X-ray source with luminosity between a star and an AGN
IMF (initial mass function): function describing initial mass of stars
IMF: see magnetic field
immersion grating: grating where light is within the material
- WINERED: near-infrared non-cryogenic spectrograph
Immirzi parameter: theoretical value relating black hole to its entropy
IMO (International Meteor Organization): amateur/professional meteor organization
IMP: see Mars Pathfinder
IMPACT (International Monitoring Programs for Asteroid and Comet Threat): 1999 IAU-sponsored conference in Italy
IMPACT: see STEREO
impact: collision of one solid body with another
impact erosion: see impact
impact parameter: see cross section
impact parameter: see transiting planet
impacts

iSALE: code modeling the shock physics of impacts
mass extinction: event in which many species went extinct
Tillotson equation: equation of state for high speed impacts

IMPS: see IRAS
IMRI: see extreme mass ratio inspiral
IMS: see Giotto
IMXB: see X-ray binary
in situ: on site
- cavity-enhanced absorption spectroscopy: passing a beam through a gas multiple times to amplify absorption lines
in situ observation: see in situ
In-situ Lunar Orientation Measurement: planned experiment to monitor lunar rotation via astrometry from the Moon
INAF (Istituto Nazionale di Astrofisica): Italian astrophysical research institute
- Astronet: European astronomy consortium
- Telescopio Nazionale Galileo: 3.58 m telescope in Canary Islands
INAG (Institut National d'Astronomie et de Geophysique): 1960s-1980s French research institute
incidence

Snell's law: optical principle of refraction

inclination (orbital inclination): angle between plane of an orbit and a reference plane
- orbital element: parameters describing an orbit
inclination-type resonance: see orbital resonance
Index Catalog: 1895 catalog of galaxies, star clusters, and other nebulae
Index Catalog of Visual Double Stars: see Washington Double Star Catalog
Index Catalogue of Nebulae and Clusters of Stars (Index Catalog): 1895 catalog of galaxies, star clusters, and other nebulae
index of refraction (refractive index): measure of how much a material slows down light
- twinkling: blinking, apparent movement and color changes of observed stars
India

AstroSat: Indian observatory satellite
Giant Metrewave Radio Telescope: large radio interferometer in India
Indian Pulsar Timing Array: group of pulsars timed by the GMRT
Indian Space Research Organisation: national science and technology agency
Inter-University Centre for Astronomy and Astrophysics: initiative promoting astrophysics at Indian universities
International Liquid Mirror Telescope: 4-meter liquid mirror telescope under construction in India
LIGO-India: planned gravitational wave detector in India
Mission Shakti: Indian antisatellite test.
Ooty Radio Telescope: cylindrical radio telescope in India
SARAS: survey aiming at highly-redshifted 21-cm detection
Tata Institute of Fundamental Research - India: Indian math and science research institute
Vainu Bappu Observatory: observatory in southern India

Indian

Aditya-L1: 2023 spacecraft viewing Sun and analyzing solar wind

Indian Initiative in Gravitational-wave Observations: see LIGO-India
Indian Pulsar Timing Array: group of pulsars timed by the GMRT
Indian Space Research Organisation: national science and technology agency
INDIGO: see LIGO-India
Indus stream

Southern Stellar Stream Spectroscopic Survey: spectroscopic survey of seven southern-hemisphere stellar streams

inelastic scattering: see scattering
inertia wave (inertial wave): type of wave in a rotating fluid
inertial forces

Reynolds number: measure reflecting a fluid system's propensity to turbulence

inertial frame (inertial reference frame): frame of reference where no force means no acceleration
inertial frame of reference (inertial reference frame): frame of reference where no force means no acceleration
inertial mass: see mass
inertial reference frame: frame of reference where no force means no acceleration
inertial wave: type of wave in a rotating fluid
infall

dynamical friction: drag produced by gravitational interaction with surrounding objects

inferior conjunction: conjunction of an "inferior planet", Venus or Mercury
inferior planet: see heliocentric system
infinitesimal transform

Lie transform: type of infinitesimal transform

infinitesimal transformation

Lie transform: type of infinitesimal transform

inflated gas giant (hot Jupiter): Jupiter-sized gas exoplanet orbiting very close to star
inflated radii: exceptionally large radii of some hot Jupiters
inflation: theorized rapid expansion of the very early universe
- alternative cosmologies: cosmological models other than Big Bang/Lambda-CDM
- cosmological simulation: simulation of the history of the universe
- early universe: from the Big Bang to recombination
- initial fluctuations: early universe density variations leading to current universe
- primordial black hole: black holes forming at the most dense volumes when inflation ceased
inflation field

quantum fluctuations: short-lived particles popping up at random

inflation theory: see inflation
inflationary theory: see inflation
information: see black-hole information paradox
Information Bulletin on Variable Stars: former 1961-2019 publication on variable stars
infrared: light with wavelength too long for our eyes to sense
- A-LIST: catalog of templates of H-band spectra for SPS
- AFGL Four Color Infrared Sky Survey: 1970s infrared survey
- AKARI: Japanese space infrared telescope
- ARIEL: planned space mission for exoplanet spectrography
- ARO 12m Telescope: twelve meter microwave telescope at KPNO
- Atacama Submillimeter Telescope Experiment: 10-meter submillimeter telescope in Chile
- AtLAST: concept for submillimeter survey telescope in Chile
- BOOMERanG: 1990s-2000s balloon-borne 1.3-meter millimeter telescope
- Canada-France-Hawaii Telescope: 3.6-meter optical/infrared telescope in Hawaii
- Catalog of Infrared Observations: collection of infrared observation data from numerous sources
- CCAT: 25-meter submillimeter telescope plan for Chile
- CEERS: JWST early release observation program covering the EGS
- Cerro Tololo Inter-American Observatory: NOIRLab observatory in Chile with Blanco telescope
- chopping mirror: internal pivoting mirror to slightly change the instrument's aim
- Cosmic Background Explorer: 1989 satellite for surveying the CMB
- cosmic infrared background: widespread infrared radiation not associated with known sources
- CRIRES: high resolution IR echelle spectrometer
- Darwin: past plan for space telescopes acting as an interferometer
- Deep Multicolor Survey: 1990s optical and infrared deep survey
- electromagnetic spectrum: spectrum of EMR
- ESO 3.6m Telescope: reflector telescope at La Silla
- Euclid: survey observatory-satellite to measure dark energy
- European Southern Observatory Very Large Telescope: four 8.2-meter optical telescopes in Chile that can act together
- far infrared: infrared radiation with wavelengths in the 30-450 μm range
- FINESSE: planned space mission for exoplanet spectrography
- Fred Lawrence Whipple Observatory: observatory near Amado, Arizona
- Fred Young Submillimeter Telescope: 6-meter submillimeter survey telescope under construction in Chile
- Gaia: astrometry survey satellite launched in 2013
- Galileo Observatory: 1960s-1970s infrared observatory aircraft
- Gattini-IR: IR transient survey telescope
- Gemini Observatory: pair of telescopes in Hawaii and Chile
- Gemini Planet Imager: infrared instrument to overcome signal noise imaging exoplanets
- Gran Telescopio Canarias: 10.4 meter telescope in the Canary Islands
- GUSTO: balloon-borne 0.9-m far-infrared telescope
- Herschel Space Observatory: infrared observatory-satellite with 3.5-meter reflector
- High Definition Space Telescope: proposed 12-meter space telescope
- Hubble Space Telescope: observatory-satellite with 2.4-meter reflective telescope
- hyperluminous infrared galaxy: a galaxy emitting a more far infrared than an ULIRG
- I band: passband for near-infrared light
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
- infrared dark cloud: molecular cloud not emitting nor transmitting infrared
- infrared excess: more infrared than that of a star's typical spectrum
- infrared source: astronomical object producing observable infrared
- Infrared Space Observatory: 1990s 60-cm infrared space telescope
- Infrared Survey Facility: 140 cm reflector telescope that images in infrared
- Infrared Telescope Maffei: 80 cm infrared telescope in Antarctica
- IOTA: past optical interferometer in Arizona
- IPAC: Caltech group to collect and analyze infrared observations
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRSA: archive center for infrared data from NASA missions
- IRTF: Mauna Kea 3-meter infrared telescope
- IRTS: 15-cm infrared telescope on Japanese satellite
- J band: atmospheric window centered around 2.2 microns, or 136 THz
- James Clerk Maxwell Telescope: far-infrared telescope in Hawaii
- James Webb Space Telescope: 6.5-meter infrared space telescope at L2
- K band: atmospheric window centered around 2.2 microns, or 136 THz
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Kitt Peak National Observatory: NOIRLab observatory in Arizona with Mayall telescope
- Kuiper Airborne Observatory: infrared observatory-plane in the 1980s
- Large Binocular Telescope: dual 8.4 meter telescope in Arizona
- Large Millimeter Telescope: large microwave telescope in Mexico
- Large Submillimeter Telescope: concept for a 50-meter submillimeter telescope in Chile
- LiteBIRD: planned spacecraft to map CMB polarization
- low-surface-brightness galaxy: galaxies less bright than those historically identified
- Lowell Discovery Telescope: 4.3 m telescope at Lowell Observatory, Arizona
- luminous infrared galaxy: a galaxy emitting a lot of far-infrared light
- LUVOIR: plan for a space-based telescope
- Magellan Telescopes: pair of 6.5 m optical telescopes in Chile
- MAXIMA: 1998-1999 balloon-borne 1.3-meter millimeter telescope
- mid infrared: infrared radiation with wavelengths in the 7.5-25 μm range
- Midcourse Space Experiment: 1990s space telescope
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Mount Wilson Observatory: Los Angeles observatory with Hooker telescope
- Munich Near-Infrared Cluster Survey: 1990s-2000s galaxy cluster survey
- near infrared: electromagnetic radiation in the range of 750-2500 nm
- NEO Surveyor: planned space observatory to detect and monitor NEOs
- New Technology Telescope: 3.58-meter reflector telescope in Chile
- NIRCam: near infrared imager on JWST
- NIRPS: near-infrared extension to HARPS spectrograph
- NIRSpec: near infrared spectrograph on JWST
- obscured fraction-luminosity relation: relation between AGN luminosity and surrounding dust IR emission
- OH/IR source: AGB star with strong OH maser
- OIR: "band name" that means both visible light and infrared
- Origins Space Telescope: concept for 2030s large space IR telescope
- post-starburst galaxy: galaxy indicating star formation some time back
- PRIMA: plan for 2030s NASA 1.8-m FIR space telescope
- R band: band of visible light around 6500 angstroms
- Roman Space Telescope: proposed near-infrared space observatory
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- Simultaneous Quad Infrared Imaging Device: NOAO instrument imaging in four infrared bands at once
- SOFIA: aircraft-based infrared observatory
- SpeX: a medium-resolution infrared spectrograph
- SPICA: plan for a future space IR telescope
- SPIRou: CFHT spectropolarimeter for exoplanet research
- Spitzer Extragalactic Representative Volume Survey: infrared survey of some well-studied fields
- Spitzer Space Telescope: retired infrared space telescope
- starburst galaxy: galaxy forming stars at a very high rate
- Subaru Telescope: 8.2-meter telescope in Hawaii
- submillimeter galaxy: galaxy that produces significant submillimeter radiation
- Submillimeter Telescope: 10-meter far-infrared telescope
- Swedish-ESO Submillimetre Telescope: 1990s 15 m submillimeter telescope in Chile
- Telescopio Nazionale Galileo: 3.58 m telescope in Canary Islands
- thermal infrared: infrared emission due to black body radiation
- total infrared: typically meaning a wide wavelength range covering NIR to FIR
- total infrared luminosity: luminosity over a wide IR range
- TripleSpec: near-infrared spectrograph on the Hale Telescope
- Two Micron All-sky Survey: near-infrared survey of both hemispheres
- Two Micron Sky Survey: 1969 infrared catalog produced by Caltech
- UKIDSS: five-part infrared survey using UKIRT
- ultraluminous infrared galaxy: a galaxy emitting a more far infrared than an LIRG
- United Kingdom Infrared Telescope: Mauna Kea 3.8 meter infrared telescope
- University of Tokyo Atacama Observatory: observatory for a 6.5 m infrared telescope under construction
- UVJ diagram: diagram to identify star formation in distant galaxies
- UVOIR: a spectral "band name" covering UV, visible light, and IR
- VISTA: 4.1 meter telescope in Paranal Observatory in Chile
- Wide Field Infrared Explorer: partly-failed 1999 infrared satellite
- William Herschel Telescope: 4.2-meter telescope in the Canary Islands
- WINERED: near-infrared non-cryogenic spectrograph
Infrared Astronomical Satellite (IRAS): 1983 satellite that surveyed the sky in infrared
infrared astronomy: see infrared
Infrared Catalog (Two Micron Sky Survey): 1969 infrared catalog produced by Caltech
infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
infrared dark cloud: molecular cloud not emitting nor transmitting infrared
infrared excess: more infrared than that of a star's typical spectrum
Infrared Imaging Surveyor (AKARI): Japanese space infrared telescope
infrared light (infrared): light with wavelength too long for our eyes to sense
infrared luminosity: see infrared
Infrared Optical Telescope Array (IOTA): past optical interferometer in Arizona
Infrared Processing and Analysis Center (IPAC): Caltech group to collect and analyze infrared observations
infrared radiation (infrared): light with wavelength too long for our eyes to sense
Infrared Science Archive (IRSA): archive center for infrared data from NASA missions
infrared source: astronomical object producing observable infrared
infrared source: see source
- radio source: astronomical object producing observable radio
Infrared Space Observatory: 1990s 60-cm infrared space telescope
Infrared Spatial Interferometer: see Mount Wilson Observatory
Infrared Survey Facility: 140 cm reflector telescope that images in infrared
Infrared Telescope Facility (IRTF): Mauna Kea 3-meter infrared telescope
- SpeX: a medium-resolution infrared spectrograph
InfraRed Telescope in Space (IRTS): 15-cm infrared telescope on Japanese satellite
Infrared Telescope Maffei: 80 cm infrared telescope in Antarctica
infrared window: see atmospheric window
ING (Isaac Newton Group of Telescopes): three telescopes in Canary Islands
- Isaac Newton Telescope: 2.5 m telescope in Canary Islands
Ingenuity: see Mars 2020
ingress duration: see transiting planet
INGRID: see William Herschel Telescope
initial fluctuation spectrum: the power spectral density of the early universe
initial fluctuations: early universe density variations leading to current universe
- initial fluctuation spectrum: the power spectral density of the early universe
initial mass function: function describing initial mass of stars
- mass function: measure of binaries that constrains the masses
initiative

Astro2020: initiative suggesting major survey efforts over the 2020-2030 decade
Black in Astro: advocacy initiative
Snowmass: initiative recommending the next decade's particle physics strategy

INMS: see Cassini
Inner Cloud (Hills Cloud): cloud of comets and minor planets around the solar system
inner Lindblad resonance: see Lindblad resonance
inner Lindblad resonance: see Lindblad torque
inner moon: see Enceladus
Inner Oort Cloud (Hills Cloud): cloud of comets and minor planets around the solar system
inner solar system

solar system object: the Sun, solar system planets, minor planets, comets, and moons

inner working angle: see coronagraph
inner-Earth object: see near-Earth object
innermost stable circular orbit: border of region surrounding a BH in which orbits are unstable
Inouye Solar Telescope (DKIST): 4 m solar telescope at Haleakala Observatory
InPTA (Indian Pulsar Timing Array): group of pulsars timed by the GMRT
INS: see neutron star
InSAR: see synthetic aperture radar
- VERITAS: planned NASA Venus orbiter
inside-out growth: tendency of galaxy star formation to spread from the center
InSight: NASA Mars mission to study its interior
Insight (HXMT): space X-ray observatory launched in 2017
insolation: solar energy received per unit area in given time
inspiral: like an orbit that is growing smaller
inspiral: see orbital decay
instability region: region around an object where orbits cannot persist
instability strip: region of H-R diagram where stars are unstable
instellation: see insolation
Institut de radioastronomie millimétrique: organized radio astronomy collaboration between France, Germany, and Spain
Institut für Theoretische Astrophysik (Institute of Theoretical Astrophysics): Heidelberg research institute
Institut National d'Astronomie et de Geophysique: 1960s-1980s French research institute
Institute for Advanced Study: research institution
Institute for Astronomy: U Hawaii astronomy research organization
Institute for Pale Blue Dots (Carl Sagan Institute): group researching finding life on other planets and moons
Institute for research on exoplanets: U Montreéal division researching exoplanets
Institute for Space Astrophysics and Planetology (Istituto di Astrofisica e Planetologia Spaziali): Italian astrophysical research institute within INAF
Institute for Theoretical and Experimental Physics

ITEP-SAI Supernova Light Curve Catalogue: online catalog

Institute of Astronomy: Cambridge U astronomy research organization
Institute of Electrical and Electronics Engineers: professional engineering association
- ITU: international body coordinating communications technology
Institute of Space and Astronautical Science: Japanese national research organization
Institute of Space and Atmospheric Studies: U Saskatchewan research division
Institute of Theoretical Astronomy: former Cambridge U astronomy research organization
Institute of Theoretical Astrophysics: Heidelberg research institute
Instituto de Astrofísica de Canarias: research institute on Canary Islands
instrument

4MOST: spectrograph in development for VISTA telescope
ACBAR: instrument used in a CMB survey
ACES: a spectrometer used to view the corona during eclipses
ACIS: imaging spectrometer on Chandra X-ray telescope
ADC Backend For Bolometer Array: APEX instrument
Air-SPEC: a spectrometer used to view the corona during eclipses
AMS-02: particle detector on ISS
ASPIRE: mechanism to stabilize observations from an airplane
CAPMAP: early 2000s array that surveyed CMB polarization
CfA digital speedometer: 1980s/90s spectrograph aimed at radial velocity measurements
comparator: device to compare the position of objects on plates
CONCERTO: spectrometer aimed at mapping the [CII] line
CorMASS: near-infrared spectrograph
COSIE: EUV spectrograph to analyze the corona
COSMOSOMAS: 1990s-2000s microwave survey
CRIRES: high resolution IR echelle spectrometer
Dark Energy Spectroscopic Instrument: new instrument for measuring red-shift of distant objects
DESHIMA: submillimeter spectrometer
electron beam ion trap: lab instrument to create ions for study
eROSITA: Russian/German space X-ray telescope launched in 2019
ESIS: EUV spectrograph for solar corona observation
EXPRES: Yale HRS spectrometer aimed at exoplanet detection
G-CLEF: spectrograph on the GMT
Gemini Planet Imager: infrared instrument to overcome signal noise imaging exoplanets
GISMO: 2 mm bolometer camera on IRAM 30 m telescope
Global-scale Observations of the Limb and Disk: satellite instrument to study ionosphere regarding space weather
GPU Supercomputer for Theoretical Astrophysics Research: supercomputer at Swinburne University
GUPPI: radio-telescope back-end aimed at processing pulsar data
HARMONI: spectrograph planned for E-ELT
HARPS: high-precision spectrograph for exoplanet searches
HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
HERMES: four-channel spectrograph on the Anglo-Australian Telescope
In-situ Lunar Orientation Measurement: planned experiment to monitor lunar rotation via astrometry from the Moon
Keck Planet Finder: Keck I spectrograph for RV measurements
Keck Planet Imager and Characterizer: extreme AO upgrade under development for Keck
KMOS: 2-micron spectrograph on ESO VLT
Large Area Debris Collector: planned ISS instrument to collect space debris for analysis
linearly variable filter: filter whose passband varies over one spatial dimension
MICADO: camera planned for E-ELT
Mimir: multi-function near-infrared instrument on Perkins Telescope
Multi-object Optical and Near-IR Spectrograph: advanced spectrograph under development for VLT
MUSTANG: bolometer array on the Green Bank Telescope
NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
NIRPS: near-infrared extension to HARPS spectrograph
null corrector: instrument for testing mirrors
PAMELA: cosmic ray detector attached to satellite
phase plate: filter that changes the phase of light passing through
plate measuring machine: machine to measure position of images on photographic plates
POLARBEAR: instrument to map CMB polarization
proportional counter: type of ionizing-radiation sensor that senses photon energy
PUPPI: Arecibo radio-telescope instrument aimed at observing pulsars
QUEST: sixteen square-degree survey camera
RELIKT-1: instrument on 1980s Soviet satellite to view the CMB
SCUBA: submillimeter instrument on James Clark Maxwell Telescope
Simultaneous Quad Infrared Imaging Device: NOAO instrument imaging in four infrared bands at once
sounding rocket: sub-orbital rocket to carry out measurements
SpeX: a medium-resolution infrared spectrograph
SPHERE: VLT instrument for imaging exoplanets
SPIRou: CFHT spectropolarimeter for exoplanet research
Subaru PFS: multi-object spectrograph in development for the Subaru telescope
TAIPAN: multi-object spectrograph with robot fiber-positioner
TolTEC: sensitive infrared camera under construction for the LMT
Tomographic Ionized-carbon Mapping Experiment: instrument in development to map the [CII] line
TripleSpec: near-infrared spectrograph on the Hale Telescope
UVSC Pathfinder: instrument to observe the Sun
WEAVE: multi-object spectrograph on the WHT
WFC3: general purpose camera/spectroscope on HST
Wide-field Multi-object Spectrograph: proposed instrument to detect baryon acoustic oscillations
WINERED: near-infrared non-cryogenic spectrograph

instrument type

astrolabe: ancient instrument to determine to date, time, and location information from the sky
bolometer: instrument measuring heat produced by radiation
CCD: type of electronic device to detect light
Cherenkov detector: type of high energy photon or particle detector
chopping mirror: internal pivoting mirror to slightly change the instrument's aim
collimator: device to align beams of light
cross-staff: historical device for measuring angular distances
CTIS: imaging spectrometer using CT algorithm to sort out overlapping orders
dark matter detector: type of particle detector attempting to detect WIMPs
dewar: term used re cryogenics for vacuum-insulated containers
downconverter: device that reduces the frequency of a signal
Fabry-Pérot interferometer: type of chromatic-dispersing interferometer
feedhorn: feature of microwave receivers
fiber positioner: machine to set up fibers in multi-object spectrograph
filter bank: set of filters to simultaneously produce radio data within bands
gas pixel detector: type of X-ray imager sensitive to polarization
Geiger-avalanche photodiode: type of solid state photon sensor
GPU: type of CPU tailored to handling computer graphics
gravitational-wave detector: device to detect gravitational waves
heterodyne spectrometer: type of millimeter/submillimeter spectrometer
imager: essentially a word for camera, produces 2D image over some bandwidth
imaging Fourier transform spectroscopy: Michelson-interferometer-based imaging spectroscopy
imaging spectrometer: device to capture spectrum point-by-point of an image
integral field spectrograph: spectrograph that captures images
integral field unit: instrument to allow a spectrograph to capture data over a 2D field
KID: type of sensitive electronic device to detect light
Langmuir probe: plasma sensor
laser: maser-like device for visible light
Lyot coronagraph: original coronagraph design
magnetometer: instrument to measure the strength of a magnetic field
mass spectrometer: device to determine the mass of molecules in a mixture
meridian circle: instrument for timing the passage of stars over a meridian
microcalorimeter: instrument to measure small amounts of heat
microchannel array: electronic device to EMR
multi-object spectrograph: device to record the spectrum of multiple targets simultaneously
multichroic feedhorn array: radio array with sensors for two or more bands
neutrino observatory: device to detect neutrinos
neutron spectrometer: device determining the energy of received free neutrons
particle spectrometer: device to determine the characteristics of incoming particles
photocathode: type of device producing free electrons from photons
photodiode: class of solid state device to detect EMR
photometer: instrument measuring brightness
photomultiplier tube: electronic device to detect light
radar: probe based on reflecting radio waves
radiometer: device for measuring radiant flux
scintillator: instrument part designed to respond to high-energy photons
slitless spectrograph: spectrograph that does not utilize a slit
sounder: device to measure something at another depth
spark chamber: type of ion detector
spectrograph: device to record the spectrum of incoming light
spectrometer: device to measure light by wavelength across its spectrum
spectroscope: device to study the spectrum of incoming light
SQUID: very sensitive magnetometer
superconducting quantum interference device: type of very sensitive magnetometer using Josephson junctions
superconducting tunnel junction: type of Josephson junction usable in EMR sensors
synthetic aperture radar: method of using moving radar with a stationary target
telescope: instrument to observe at a distance
transition edge sensor: sensor using superconductivity's strong temperature sensitivity
wavefront sensor: instrument for determining a wave's deformation
waveplate: type of optical device that alters polarization

instruments

adaptive optics: optical mechanism to compensate for varying atmospheric distortion
aperture masking interferometry: interferometry by means of a single telescope with a mask
back end instrument: instruments of a telescope that process or combine signals
CASPER: initiative to design radio-astronomy instruments
collecting area: cross-sectional area over which a telescope receives EMR
detective quantum efficiency: measure of instrument's ability to create images
emissivity: measure of a material's efficiency at radiating thermal radiation
etalon: two parallel reflective surfaces separating light according to wavelength
exposure time: time spent acquiring a signal
extreme adaptive optics: high-performance version of AO system
field-programmable gate array: type of customizable digital electronic circuit
focal plane array: array of receivers at the focus of a radio telescope
frequency modulation: changing the frequency of a signal's carrier
front end instrument: instruments of a telescope that detect and encode the signal
grism: combination of a grating and a prism
hot pixel: CCD pixel that shows more brightness than it should
integration time: time spent acquiring a signal
limiting magnitude: faintest magnitude that a telescope or instrument can detect
low noise amplifier: amplifier aimed at very low noise for extremely sensitive measurement
Lyot stop: optical element to block unwanted light within instruments
Multi-Pinned-Phase: type of CCD with reduced signal noise
optical axis: center line through an optical instrument
optics: science and technology regarding visible light
photon counting: sensing EMR down to the photon level
photon noise: variation in light measurement due to its quantum nature
point source sensitivity: determination of how readily an instrument detects a point source
quantum efficiency: measure of instrument's ability to sense EMR
Radio Camera Initiative: initiative to design radio interferometry correlators
Radioisotope Thermoelectric Generator: type of spacecraft power source for instruments
Santa Barbara Instrument Group: old name of Santa Barbara Scientific, telescope instrument manufacturer
speckle suppression: methods of reducing noise in telescope observations
spectral resolution: measure of a spectrograph's ability to resolve features of the spectrum
systematic error: errors with non-random characteristics
thermal noise: noise inherent in electronic component warmer than absolute zero
wavefront error: measure of a class of telescope distortion

INT (Isaac Newton Telescope): 2.5 m telescope in Canary Islands
- Giant Stellar Stream: extensive stellar stream in M31
- IPHAS: H-alpha survey
- Isaac Newton Group of Telescopes: three telescopes in Canary Islands
- Millennium Galaxy Catalogue: 2000s catalog of 10,000 galaxies
- POINT-AGAPE: survey of M31 for microlensing
- Roque de los Muchachos Observatory: observatory at La Palma in the Canary Islands
- Terra Hunting Experiment: search for exoplanets using HARPS3
- William Herschel Telescope: 4.2-meter telescope in the Canary Islands
- X-SHOOTER Lyman α survey at z = 2: survey of Lyman-α sources
INT Galactic Plane Survey: see IPHAS
INT Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS): H-alpha survey
INT Photometric Halpha Survey (IPHAS): H-alpha survey
INTEGRAL: European gamma ray observatory-satellite
INTEGRAL: see William Herschel Telescope
- integral field spectrograph: spectrograph that captures images
- integral field unit: instrument to allow a spectrograph to capture data over a 2D field
INTEGRAL Burst Alert System: see INTEGRAL
integral field spectrograph: spectrograph that captures images
- data cube: three-dimensional array of numerical data
integral field spectrometer (integral field spectrograph): spectrograph that captures images
- imaging spectrometer: device to capture spectrum point-by-point of an image
integral field spectroscopy: see integral field spectrograph
integral field unit: instrument to allow a spectrograph to capture data over a 2D field
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
integrated flux nebula: fuzzy illuminated nebula within Milky Way halo
integrated Sachs-Wolfe effect: see Sachs-Wolfe effect
integration time: time spent acquiring a signal
- exposure time: time spent acquiring a signal
intensity: power reaching a surface from a specific source
- Planck function: yields black-body spectrum curve
- radiance: measure of EMR to/from a solid angle through an area
intensity interferometer: interferometer based upon interference from intensity variations
- Hanbury Brown and Twiss effect: EMR interference stemming from variation in intensity
- Narrabri Stellar Intensity Interferometer: 1960s optical interferometer for measuring stellar diameters
- optical interferometer: interferometer of visible light
intensity interferometry: see intensity interferometer
Intensity Interferometry at Calern: see GI2T
- optical interferometer: interferometer of visible light
intensity map: see intensity mapping
intensity mapping: measure of cosmic matter density
- 21-cm experiment: search for redshifted 21-cm hydrogen emission lines
- 21-cm line: hydrogen line useful for determining redshift
- AIM-CO: survey of CO from star-forming epoch
- BINGO: future radio telescope for mapping distant neutral hydrogen
- Canadian Hydrogen Intensity Mapping Experiment: radio telescope mapping distant neutral hydrogen
- CIBER: sounding-rocket survey of near-infrared background
- COMAP: high frequency radio telescope to map CO
- CONCERTO: spectrometer aimed at mapping the [CII] line
- COPSS: survey of CO from star forming epoch
- Cosmic Dawn Intensity Mapper: NASA concept for space telescope for intensity mapping
- destriping: removing streak-like noise from images
- EXCLAIM: planned balloon-borne 70-cm telescope with spectrometers
- foreground subtraction: removing unwanted sources of EMR in intensity mapping
- Fred Young Submillimeter Telescope: 6-meter submillimeter survey telescope under construction in Chile
- Hα survey: survey looking for the Hα line, typically to find star formation
- HIRAX: radio telescope array for 21-cm surveying
- intensity mapping surveys: efforts mapping the intensity of spectral lines across the sky
- MeerKLASS: 21-cm-line survey using MeerKAT
- Millimeter-wave Intensity Mapping Experiment: project to map CO and [CII]
- OVRO-LWA: radio telescope in California
- PIXIE: satellite-concept to to survey CMB polarization
- SIMSTACK: software to correlate intensity maps with sources
- SPHEREx: all-sky spectral survey space-mission plan
- Tianlai Project: 21-cm line intensity mapping project
- TIM: planned balloon-borne 2 m telescope and spectrometer
- Tomographic Ionized-carbon Mapping Experiment: instrument in development to map the [CII] line
- Yuan-Tseh Lee Array: microwave interferometer in Hawaii
intensity mapping experiments (intensity mapping surveys): efforts mapping the intensity of spectral lines across the sky
intensity mapping surveys: efforts mapping the intensity of spectral lines across the sky
- intensity mapping: measure of cosmic matter density
Inter-University Centre for Astronomy and Astrophysics: initiative promoting astrophysics at Indian universities
interacting binary: see contact binary
interacting galaxy: see galaxy interaction
- galactic tide: effect of one galaxy's gravity, such as on another galaxy
Interactive Data Language (IDL): interactive vector-oriented programming language
intercloud gas: see interstellar medium
Interféromètre a 2 Télescopes: see GI2T
- optical interferometer: interferometer of visible light
interference: result of interaction of waves
- interferometry: analysis of superimposed EMR waves
- radio frequency interference: transmissions in a frequency band under observation
interference pattern

interference: result of interaction of waves

interferometer: device detecting EMR properties using interference between waves
- Allen Telescope Array: array of radio telescopes in northern California for SETI
- 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
- CHARA: optical interferometer on Mount Wilson
- COAST: optical interferometer in England
- Combined Array for Research in Millimeter-wave Astronomy: former array of radio telescopes in eastern California
- Cosmic Anisotropy Telescope: 1990s interferometer to measure CMB variations
- Cosmic Explorer: concept for a very large LIGO-like GW detector
- Darwin: past plan for space telescopes acting as an interferometer
- DASI: 2000-2003 South Pole CMB telescope
- DECIGO: proposed Japanese space mission to detect gravitational waves
- Einstein Telescope: concept for a larger LIGO-like GW detector
- GEO600: ground-based gravitational-wave detector in Germany
- GI2T: optical interferometer in France
- Giant Metrewave Radio Telescope: large radio interferometer in India
- IOTA: past optical interferometer in Arizona
- KAGRA: gravitational wave detector in Japan preparing for operation
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- LIGO: pair of observatories to detect gravitational waves
- LIGO-India: planned gravitational wave detector in India
- LISA: proposed space mission to detect gravitational waves
- Long Baseline Array: radio interferometer using Australian telescopes
- MRO Interferometer: optical interferometer in New Mexico
- Navy Precision Optical Interferometer: optical interferometer in Arizona
- New Gravitational Wave Observatory: past proposal for space mission to detect gravitational waves
- Next Generation Very Large Array: planned radio telescope array as a follow-on to ALMA and the Jansky VLA
- Palomar Testbed Interferometer: near-infrared interferometer experiment
- PAPER: radio interferometer for 21-cm measurement
- Plateau de Bure Interferometer: 6-dish interferometer in French Alps
- Space Interferometry Mission: past space interferometer plan for parallax and exoplanet detection
- SPICE: plan for a future far-infrared space interferometer
- Square Kilometre Array: planned radio telescope with square-kilometer collecting area
- Submillimeter Array: radio interferometer in Hawaii
- SUSI: optical interferometer in Australia
- TAMA 300: small prototype gravitational wave detector in Japan
- TianQin: proposed Chinese space mission to detect gravitational waves
- 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
- Virgo: ground-based gravitational-wave detector in Italy
- Yuan-Tseh Lee Array: microwave interferometer in Hawaii
interferometric synthetic aperture radar: see synthetic aperture radar
- VERITAS: planned NASA Venus orbiter
interferometry: analysis of superimposed EMR waves
- aperture masking interferometry: interferometry by means of a single telescope with a mask
- aperture synthesis: interferometry to simulate a larger aperture telescope
- Astronomical Image Processing System: software for processing radio astronomy data
- baseline: distance between dishes of an interferometer
- CASA: software package for radio interferometry image generation
- CLEAN: algorithm to extract usable images from interferometry-produced images
- correlator: unit that interferes wave signals for interferometry
- dirty image: image that includes the distortions of the beam and sampling
- Earth rotation synthesis: using the Earth's rotation to observe with various interferometry baselines
- Earth-sized VLBI: ground-based VLBI with near-maximal baseline
- electronic very-long-baseline interferometry: real-time VLBI using electronic links
- Fabry-Pérot interferometer: type of chromatic-dispersing interferometer
- Hanbury Brown and Twiss effect: EMR interference stemming from variation in intensity
- high-resolution imaging: typically, imaging with resolution better than a milliarcsecond
- intensity interferometer: interferometer based upon interference from intensity variations
- interferometer: device detecting EMR properties using interference between waves
- optical interferometer: interferometer of visible light
- Sagnac effect: an effect of the movement of light beams regarding their interference
- speckle masking: speckle suppression technique using a calculation of the bispectrum
- spectral correlator: correlator that also functions as a spectrograph
- u-v plane: plane for displaying Fourier transforms of signal from the sky
- van Cittert-Zernike theorem: interferometer-visibilities equal the Fourier transform of the source
- very-long-baseline interferometry: interferometry based upon storing timing data at each telescope
- visibility: mathematical representation of interferometer's view
intergalactic dust: dust not within galaxies
intergalactic HI cloud: cloud of HI not within any galaxy
intergalactic medium: matter between galaxies
- intracluster medium: hot plasma throughout a galaxy cluster
Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight): NASA Mars mission to study its interior
interloper: see intensity mapping
intermediate band: see passband
intermediate band photometry: see photometry
intermediate luminosity optical transient: visible-light transient a bit brighter than a nova
intermediate mass ratio inspiral: see extreme mass ratio inspiral
intermediate polar: see variable star
intermediate spiral galaxy: see galaxy classification
- NGC 6946: face-on spiral galaxy
intermediate-mass black hole: black hole between stellar mass and supermassive
- black hole: region of such high mass that light cannot escape
- extreme mass ratio inspiral: inspiraling pair of objects with mass ratio beyond 10,000
- ultraluminous X-ray source: X-ray source with luminosity between a star and an AGN
intermediate-mass X-ray binary: see X-ray binary
intermediate-velocity cloud: see high-velocity cloud
internal gravity wave: ripples in a change in density in a fluid
internal wave (internal gravity wave): ripples in a change in density in a fluid
international

International Amateur-Professional Photoelectric Photometry: organization active 1980-2000+

International Active Sun Years: 1969-1971 initiative for solar surveys
International Amateur-Professional Photoelectric Photometry: organization active 1980-2000+
International Astronomical Union: association of professional astronomers
- FITS: IAU standard for data such as images
- galactic coordinate system: celestial coordinate system system based upon the galactic plane
- Minor Planet Center: organization collecting and organizing minor planet data
International Astronomical Youth Camp: summer camp
International Atomic Time: see Terrestrial Time
International Celestial Reference Frame (ICRF): celestial reference frame based upon quasars
- celestial reference frame: frame of reference associated with a catalog of stars or quasars
- International Celestial Reference System: standardized variation of equatorial coordinate system
International Celestial Reference System: standardized variation of equatorial coordinate system
- celestial coordinate system: system for specifying position of celestial objects
- Gaia Celestial Reference Frame: celestial reference frame based upon Gaia data
- Hipparcos Celestial Reference Frame: astronomical reference frame based upon Hipparcos catalog
- ICRF: celestial reference frame based upon quasars
International Comet Quarterly: journal regarding comets
International Cometary Explorer: 1980s space mission flying by comets
International Coordinate Reference Frame: see International Celestial Reference System
International Coordinate Reference System: see International Celestial Reference System
International Cosmic Ray Conference: bi-annual cosmic ray conference since 1947
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 Earth Rotation Service (International Earth Rotation and Reference Systems Service): service monitoring Earth's rotation and precession
International Gamma-ray Astrophysics Laboratory (INTEGRAL): European gamma ray observatory-satellite
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 Liquid Mirror Telescope: 4-meter liquid mirror telescope under construction in India
International Meteor Organization: amateur/professional meteor organization
International Monitoring Programs for Asteroid and Comet Threat: 1999 IAU-sponsored conference in Italy
International Occultation Timing Association: volunteer organization to observe occultations
International Organization for Standardization: standards-development organization
International Pulsar Timing Array: organization of pulsar timing arrays
International Quiet Sun Year: 1964-1965 initiative for solar surveys
International Robotic Antarctic Infrared Telescope (Infrared Telescope Maffei): 80 cm infrared telescope in Antarctica
International Scientific Optical Network: project to track objects in space
International Small Telescope Cooperative: former cooperative of small research telescopes
International Solar Polar Mission (Ulysses): space mission to observe the Sun from off the ecliptic
International Space Station: long-term manned space station operated by numerous nations
- AMS-02: particle detector on ISS
- COSIE: EUV spectrograph to analyze the corona
- EUSO-SPB: balloon-borne cosmic ray observatory
- MAXI: Japanese X-ray camera on the International Space Station
- NICER: space X-ray mission specifically to view neutron stars
International Space Year: 1992 initiative re space and astronomy
International Sun-Earth Explorer: see International Cometary Explorer
International Supernova Network: SN information sharing initiative
International System of Units (SI): standardized metric system
- CGS: metric system variant
International Telecommunication Union (ITU): international body coordinating communications technology
International Ultraviolet Explorer: 1980s ultraviolet space telescope
International Variable Star Index: variable star catalog by AAVSO
International Virtual Observatory Alliance: see virtual observatory
International Workshop for Astronomy: organization operating the IAYC
International Workshop on Cometary Astronomy: occasional meeting
interplanetary dust: see cosmic dust
interplanetary dust cloud: see cosmic dust
interplanetary dust particle: see interplanetary medium
interplanetary magnetic field: see magnetic field
interplanetary medium: matter in the solar system around and between planets
Interplanetary Physics Laboratory (Wind): spacecraft measuring solar wind
interplanetary scintillation: see scintillometry
- Interplanetary Scintillation Array: UK radio telescope that first detected pulsars
Interplanetary Scintillation Array: UK radio telescope that first detected pulsars
- Mullard Radio Astronomy Observatory: radio observatory near Cambridge, UK
interpretation

CO to H₂ factor: assumed ratio between observed CO emission lines and H₂ mass

interstellar astronomy (interstellar astrophysics): astronomy of the ISM including dust and clouds
interstellar astrophysics: astronomy of the ISM including dust and clouds
Interstellar Boundary Explorer: satellite observing the ISM/heliosphere boundary
interstellar cloud (cloud): higher-density region of space
interstellar dust: see cosmic dust
interstellar extinction: see extinction
interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
interstellar magnetic field: galactic magnetic field between that of stars
Interstellar Mapping and Acceleration Probe (IMAP): future solar science probe
interstellar matter (interstellar medium): matter within a galaxy between star systems
interstellar medium: matter within a galaxy between star systems
- 2175 angstrom feature: prominent absorption feature in ISM
- shell: hollow shaped region of some kind of ISM
- supershell: very large ISM shell-shaped region
Interstellar Medium Absorption Profile Spectrograph: 1980s/1990s UV spectrometer
interstellar planet (free-floating planet): planet that is not orbiting a star
interstellar planet: see field
interstellar radiation field: EMR throughout the "empty" space of a galaxy
interstellar reddening (reddening): red appearance of astronomical objects because blue light is attenuated by dust
interstellar scintillation: see scintillometry
intertropical convergence zone: circulation pattern near equator where north and south Hadley cells meet
Intracluster: region between objects of a cluster such as between stars in a star cluster
intracluster gas (intracluster medium): hot plasma throughout a galaxy cluster
intracluster medium: hot plasma throughout a galaxy cluster
- intergalactic medium: matter between galaxies
intraday variable: see variable star
intrinsic color index: see color index
intrinsic S-star: see S-type star
intrinsic variable: see variable star
inverse beta decay: see beta decay
- neutronization: an electron and proton combining to form a neutron
inverse bremsstrahlung: see bremsstrahlung
inverse Compton: see Compton scattering
inverse Compton scattering: see Compton scattering
- non-thermal emission: EMR not due to a body's heat
- Sunyaev-Zel'dovich effect: type of distortion of the CMB
- synchrotron self-Compton: charged particle cloud scattering its own synchrotron-produced photons
inverse discrete Fourier transform: see fast Fourier transform
inverse Fourier transform: see Fourier transform
- Fourier series: type of series able to approximate a periodic function
inverse model: see forward model
- retrieval: determining parameters through observation and modeling
- Tau-REx: spectral line retrieval code for exoplanet atmospheres
inverse Radon transform: see tomography
inverse square law: a value's dependency upon reciprocal of the square of the distance from something
inverse volume weighting (volume weighting): method of accommodating the Malmquist bias
Io: well-known Jupiter moon
Io plasma torus: see Io
Io torus: see Io
IO:I: see Liverpool Telescope
IO:O: see Liverpool Telescope
IoA (Institute of Astronomy): Cambridge U astronomy research organization
IOK: see rare designator prefixes
ion: non-neutral atom or molecule, with missing or extra electrons
- C⁺: ionized carbon missing one electron
- HCO⁺: ionized compound of hydrogen, carbon, and oxygen, one atom each
- HZE ion: fast-moving metal atom triply-ionized or more
- solar energetic particle: high-energy particles from the Sun
- solar particle: particles from the Sun such as the solar wind
- spark chamber: type of ion detector
- state of ionization: difference in an ion's electron count versus proton count
ion engine: type of electrical spacecraft engine
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
ion thruster (ion engine): type of electrical spacecraft engine
ionic bond: see ion
- adsorption: adhesion to a surface
- oxidation state: number of electrons loaned out by an atom in an ionic bond
ionic ocean: see zonal flow
ionization (state of ionization): difference in an ion's electron count versus proton count
- acidity: measure of the activity of hydrogen ions in a solution
- binding energy: energy needed to separate two objects
- dark age: interval when the universe's hydrogen atoms were neutral
- degree of ionization: fraction of material consisting of ions
- epoch of reionization: time when the universe's neutral hydrogen atoms ionized
- HII region: cloud of partially-ionized atomic hydrogen
- instability strip: region of H-R diagram where stars are unstable
- ion: non-neutral atom or molecule, with missing or extra electrons
- ionization correction factor: relations between ion abundances and element abundances
- ionization fraction: a substance's ratio of unattached electrons to nuclei
- ionization potential: energy needed to ionize an atom
- ionized hydrogen: state of hydrogen when sufficiently hot
- ionizing radiation: radiation with photon energy sufficient to ionize
- kappa mechanism: stellar instability caused by opacity increasing with temperature
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- neutral atomic hydrogen: state of hydrogen when sufficiently cool
- partial ionization zone: portion of some stars where gas is partially ionized
- photodissociation region: cloud of partially-ionized atomic hydrogen
- photoionization: photon striking neutral atom expelling an electron
- recombination: time when the universe's ionized hydrogen atoms neutralized
- Saha equation: equation relating ionization to temperature
- Strömgren sphere: sphere of ionized hydrogen around an OB star
- Z+: symbol for ion or ion charge
ionization chamber

proportional counter: type of ionizing-radiation sensor that senses photon energy

ionization correction factor: relations between ion abundances and element abundances
ionization energy (ionization potential): energy needed to ionize an atom
ionization fraction: a substance's ratio of unattached electrons to nuclei
ionization front

molecular hydrogen dissociation front: point in a gas cloud where it is hot enough to dissociate hydrogen

ionization potential: energy needed to ionize an atom
ionization state

Saha equation: equation relating ionization to temperature

ionization temperature: see temperature
ionization valve (kappa mechanism): stellar instability caused by opacity increasing with temperature
ionize: see state of ionization
ionized carbon fine structure line: carbon line that traces distant star formation
ionized carbon forbidden line (ionized carbon fine structure line): carbon line that traces distant star formation
ionized hydrogen: state of hydrogen when sufficiently hot
- proximity effect: Ly-α forest characteristics revealing quasar history
ionized interstellar medium

interstellar medium: matter within a galaxy between star systems

ionizing photon: see ionizing radiation
ionizing radiation: radiation with photon energy sufficient to ionize
- extreme ultraviolet: electromagnetic radiation in the range of 10-124 nm
ionosphere: layers of Earth atmosphere with significant ions
- space weather: varying conditions in space affecting Earth and humans
ions

spark chamber: type of ion detector

ioschrone

Dartmouth Stellar Evolution Database: database relating isochrones to stellar parameters

IOTA: past optical interferometer in Arizona
IOTA (International Occultation Timing Association): volunteer organization to observe occultations
IPAC: Caltech group to collect and analyze infrared observations
IPC: see HEAO-2
IPHAS: H-alpha survey
IPHASX: see IPHAS
IPM (interplanetary medium): matter in the solar system around and between planets
IPMO (free-floating planet): planet that is not orbiting a star
IPMO: see planetary mass object
IPS: see scintillometry
IPS Array (Interplanetary Scintillation Array): UK radio telescope that first detected pulsars
- Mullard Radio Astronomy Observatory: radio observatory near Cambridge, UK
IPTA (International Pulsar Timing Array): organization of pulsar timing arrays
IPTA+: see International Pulsar Timing Array
iPTF: see Palomar Transient Factory
- Zwicky Transient Facility: survey designed to find transients
IQSY (International Quiet Sun Year): 1964-1965 initiative for solar surveys
IR (infrared): light with wavelength too long for our eyes to sense
IR excess (infrared excess): more infrared than that of a star's typical spectrum
IR SFR: see star formation rate
IR source: see source
- radio source: astronomical object producing observable radio
IR star formation rate: see star formation rate
IRAC: see Spitzer Space Telescope
- IRAC Shallow Survey: Spitzer survey of moderately wide field
- Spitzer Extragalactic Representative Volume Survey: infrared survey of some well-studied fields
IRAC Shallow Cluster Survey: see IRAC Shallow Survey
IRAC Shallow Survey: Spitzer survey of moderately wide field
IRAF (Image Reduction and Analysis Facility): NOAO-developed image manipulation/viewing software
IRAIT (Infrared Telescope Maffei): 80 cm infrared telescope in Antarctica
IRAM (Institut de radioastronomie millimétrique): organized radio astronomy collaboration between France, Germany, and Spain
- COLD GASS: survey of CO in nearby large galaxies
- GISMO: 2 mm bolometer camera on IRAM 30 m telescope
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- Northern Extended Millimeter Array: large radio telescope array under construction in Europe
- PHIBSS: survey of CO in distant galaxies
- Plateau de Bure Interferometer: 6-dish interferometer in French Alps
IRAM 30m Millimeter Radio Telescope (IRAM 30m Telescope): millimeter-range radio telescope in Sierra Nevada, Spain
IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- EMPIRE Survey: survey of gas in M51a to follow up PAWS
IRAS: 1983 satellite that surveyed the sky in infrared
- GOALS: across-spectrum observation of 200 LIRGs
IRAS 13224-3809: active Seyfert galaxy with well-studied SMBH
IRAS 16293-2422

ALMA-PILS Survey: millimeter survey of a protostar

IRAS 22134+5834

proto-cluster: newly-formed galaxy cluster

IRAS F: see IRAS
IRAS Faint Source Catalog: see IRAS
IRAS Minor Planet Survey: see IRAS
IRAS Point Source Catalog: see IRAS
IRAS-FSC: see IRAS
IRAS-PSC: see IRAS
IRC (Two Micron Sky Survey): 1969 infrared catalog produced by Caltech
IRC: see AKARI
IRc: see rare designator prefixes
IRCAM: see United Kingdom Infrared Telescope
- Hawaii K-band Galaxy Survey: near-infrared survey of a selection of fields
IRCS: see Subaru Telescope
IRD: see Subaru Telescope
IRDC (infrared dark cloud): molecular cloud not emitting nor transmitting infrared
IRDC: see rare designator prefixes
IRDIS: see European Southern Observatory Very Large Telescope
IRDIS: see SPHERE
IREM: see INTEGRAL
iREX (Institute for research on exoplanets): U Montreéal division researching exoplanets
iridium

siderophile: material that dissolves in molten iron

IRIS (AKARI): Japanese space infrared telescope
IRIS: see Thirty Meter Telescope
IRIS: see Voyager
IRIS2: see Anglo-Australian Telescope
IRMS: see Thirty Meter Telescope
iron: metal, Fe, atomic number 26
- iron peak: peak in the distribution of abundances surrounding iron
- K-line: iron X-ray line
- Lambda Boötis star: peculiar star with metallicity only with lighter elements
- maximum iron fraction: derived from planet-formation models
- silicon burning: alpha process fusion starting at silicon
- trans-iron element: elements with atomic number greater than that of iron
iron core collapse: see core collapse
iron Kα (K-line): iron X-ray line
iron K-line (K-line): iron X-ray line
iron line (K-line): iron X-ray line
iron peak: peak in the distribution of abundances surrounding iron
- iron peak element: element near the iron peak
iron peak element: element near the iron peak
- alpha element: element created by alpha capture
- alpha-enhanced: metallicity with a high percentage of alpha elements
iron star: see exotic star
iron-56

nickel: metal, Ni, atomic number 28

IRPOL: see United Kingdom Infrared Telescope
Irr-I: see irregular galaxy
Irr-II: see irregular galaxy
irradiance: EMR power reaching a surface
irregular

Canis Major Dwarf Galaxy: small irregular galaxy in the Local Group
Sagittarius Dwarf Irregular Galaxy: most distant galaxy in the Local Group
Wolf-Lundmark-Melotte: irregular galaxy at edge of Local Group

irregular galaxy: galaxy that's not a disk or ellipsoid
- galaxy: gravitationally-bound group of stars
- galaxy classification: morphological classification of galaxies
irregular moon: moon with an atypical orbit, such as retrograde
irregular satellite (irregular moon): moon with an atypical orbit, such as retrograde
irregular variable: see variable star
IRS (infrared source): astronomical object producing observable infrared
IRS: see Spitzer Space Telescope
IRS: see infrared
IRSA: archive center for infrared data from NASA missions
IRSF (Infrared Survey Facility): 140 cm reflector telescope that images in infrared
- South African Astronomical Observatory: South African observatory with SALT telescope
IRSPEC: see New Technology Telescope
IRSV: see rare designator prefixes
IRT: see THESEUS
IRTF: Mauna Kea 3-meter infrared telescope
- Mauna Kea: Hawaiian mountain, the site of observatories
- Mauna Kea Observatories: observatories on Mauna Kea in Hawaii
- SpeX: a medium-resolution infrared spectrograph
IRTS: 15-cm infrared telescope on Japanese satellite
- Japan Aerospace Exploration Agency: Japan agency includes astronomical research
Irvine-Michigan-Brookhaven detector (IMB): 1980s neutrino detector
IRX (infrared excess): more infrared than that of a star's typical spectrum
IS☉IS-EPI: see Parker Solar Probe
ISAAC: see European Southern Observatory Very Large Telescope
- New Technology Telescope: 3.58-meter reflector telescope in Chile
Isaac Newton Group of Telescopes: three telescopes in Canary Islands
- Isaac Newton Telescope: 2.5 m telescope in Canary Islands
- William Herschel Telescope: 4.2-meter telescope in the Canary Islands
Isaac Newton Telescope: 2.5 m telescope in Canary Islands
- Giant Stellar Stream: extensive stellar stream in M31
- IPHAS: H-alpha survey
- Isaac Newton Group of Telescopes: three telescopes in Canary Islands
- POINT-AGAPE: survey of M31 for microlensing
- Roque de los Muchachos Observatory: observatory at La Palma in the Canary Islands
- Terra Hunting Experiment: search for exoplanets using HARPS3
- X-SHOOTER Lyman α survey at z = 2: survey of Lyman-α sources
iSALE: code modeling the shock physics of impacts
ISAMS: see Upper Atmosphere Research Satellite
ISAS (Institute of Space and Astronautical Science): Japanese national research organization
ISAS (Institute of Space and Atmospheric Studies): U Saskatchewan research division
ISCO (innermost stable circular orbit): border of region surrounding a BH in which orbits are unstable
ISCO-radius: see innermost stable circular orbit
ISCS: see IRAC Shallow Survey
ISEE: see International Cometary Explorer
ISEE-3: see International Cometary Explorer
iSEEP Wide-Field MAXI: see MAXI
ISEM: see Rosalind Franklin
ISG: see rare designator prefixes
ISGRI: see INTEGRAL
iShell: see IRTF
ISI: see Mount Wilson Observatory
ISIS: see William Herschel Telescope
ISM (interstellar medium): matter within a galaxy between star systems
- 2175 angstrom feature: prominent absorption feature in ISM
- Cloudy: code to model the effect of gas and plasma on spectra
- cold gas: gas cool enough to form galaxies and stars
- galactic disk: the "disk" portion of a disk galaxy
- galactic electron density: density of electrons in the ISM
- HCO⁺: ionized compound of hydrogen, carbon, and oxygen, one atom each
- hydrogen cyanide: compound of hydrogen, carbon, and nitrogen, one atom each
- interstellar astrophysics: astronomy of the ISM including dust and clouds
- interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
- interstellar radiation field: EMR throughout the "empty" space of a galaxy
- Local Interstellar Cloud: local ISM region with slightly higher density of hydrogen
- refractive interstellar scintillation: refraction of star light by the ISM
- shell: hollow shaped region of some kind of ISM
- supershell: very large ISM shell-shaped region
ISM cirrus (infrared cirrus): cirrus-cloud-like infrared emissions from dust, etc.
ISMF (interstellar magnetic field): galactic magnetic field between that of stars
ISN (International Supernova Network): SN information sharing initiative
ISO (Infrared Space Observatory): 1990s 60-cm infrared space telescope
ISO (International Organization for Standardization): standards-development organization
ISO spectrum

Infrared Space Observatory: 1990s 60-cm infrared space telescope

ISOCAM: see Infrared Space Observatory
- CEA Service d'Astrophysique: French national astrophysics research institute
isochronal fitting: method of estimating stellar age from retrievable parameters
isochrone: line of equal ages on an HRD
- BaSTI: database relating isochrones to stellar parameters
- H-R diagram: diagram relating effective temperature to luminosity
isochrone fitting (isochronal fitting): method of estimating stellar age from retrievable parameters
ISOHDFS: see Hubble Deep Field South
isolated galaxy (field galaxy): galaxy not in a cluster or group
isolated neutron star: see neutron star
isolated planetary mass object (free-floating planet): planet that is not orbiting a star
isolated planetary mass object: see planetary mass object
isolated PMO (free-floating planet): planet that is not orbiting a star
isolation mass: mass of an oligarch after accreting all nearby planetesimals
isolation mass core: see isolation mass
isolation mass planet: see isolation mass
ISON (International Scientific Optical Network): project to track objects in space
ISOPHOT: see Infrared Space Observatory
isophotal radius: see Holmberg radius
isophote: line on a diagram indicating a level of brightness
- Holmberg radius: a measure of size of galaxy based on surface brightness
isostasy: crust-mantle equilibrium
isothermal core: core region of a body of all the same temperature
isotope: subclass of an element with a specific number of nucleons
- ¹H: hydrogen isotope with no neutrons
- deuterium: hydrogen isotope with one neutron
isotope fractionation: see fractionation
- fractionation factor: isotope-related ratio
isotope notation

isotope: subclass of an element with a specific number of nucleons

isotope signature: see Moon formation
isotopes

element: class of atom based on its number of protons
mass number: number of nucleons in an atomic nucleus
nuclide: atomic nucleus associated with a specific isotope

isotopic fractionation

fractionation factor: isotope-related ratio

isotopic ratio: see abundances
isotropic radiant energy: see isotropy
isotropic radiation: see isotropy
isotropy: uniformity in all directions
- anisotropy: directional-dependence such as temperature variation around the CMB
ISPM (Ulysses): space mission to observe the Sun from off the ecliptic
Israeli

ULTRASAT: future satellite to detect UV transients

ISRF (interstellar radiation field): EMR throughout the "empty" space of a galaxy
ISRO (Indian Space Research Organisation): national science and technology agency
- Aditya-L1: 2023 spacecraft viewing Sun and analyzing solar wind
ISS (IRAC Shallow Survey): Spitzer survey of moderately wide field
ISS (International Space Station): long-term manned space station operated by numerous nations
ISS: see Cassini
ISS: see Voyager
ISS: see scintillometry
- AMS-02: particle detector on ISS
- COSIE: EUV spectrograph to analyze the corona
- EUSO-SPB: balloon-borne cosmic ray observatory
- MAXI: Japanese X-ray camera on the International Space Station
- NICER: space X-ray mission specifically to view neutron stars
ISTeC (International Small Telescope Cooperative): former cooperative of small research telescopes
Istituto di Astrofisica e Planetologia Spaziali: Italian astrophysical research institute within INAF
Istituto di Astrofisica Spaziale: former name of Italian astrophysics research institution
Istituto Nazionale di Astrofisica: Italian astrophysical research institute
ISW: see Sachs-Wolfe effect
IsWe: see rare designator prefixes
ISY (International Space Year): 1992 initiative re space and astronomy
ITA (Institute of Theoretical Astronomy): former Cambridge U astronomy research organization
ITA (Institute of Theoretical Astrophysics): Heidelberg research institute
Italian

AGILE: Italian space gamma-ray observatory
Gruppo Italiano Astrometristi: Italian amateur astronomy organization
LARES: satellite to test a general relativity effect
LSPE-SWIPE: plan for a balloon-based CMB polarization survey
NEODyS: web service to providing information on NEOs
PAMELA: cosmic ray detector attached to satellite
Telescopio Nazionale Galileo: 3.58 m telescope in Canary Islands

Italian National Institute of Astrophysics

Telescopio Nazionale Galileo: 3.58 m telescope in Canary Islands

Italian Robotic Antarctic Infrared Telescope (Infrared Telescope Maffei): 80 cm infrared telescope in Antarctica
Italian Space Agency (Agenzia Spaziale Italiana): includes space-based astronomy research
- AGILE: Italian space gamma-ray observatory
Italy

Agenzia Spaziale Italiana: includes space-based astronomy research
Bologna Survey of Radio Sources: 1970s-1980s radio survey
Borexino: European underground neutrino observatory
Campo Imperatore Near-Earth Object Survey: survey of near-Earth objects
Consiglio Nazionale delle Ricerche: Italian national research organization.
Cryogenic Rare Event Search with Superconducting Thermometers: a search for a candidate dark matter particle
CUORE: experiment to sense neutrinoless double beta decay
DAMA/LIBRA: dark matter detection experiment in Italy
European Gravitational Observatory: gravitational wave observatory in Italy
Istituto di Astrofisica e Planetologia Spaziali: Italian astrophysical research institute within INAF
Istituto di Astrofisica Spaziale: former name of Italian astrophysics research institution
Istituto Nazionale di Astrofisica: Italian astrophysical research institute
Sardinia Radio Telescope: Italian large single-dish radio telescope
Virgo: ground-based gravitational-wave detector in Italy

ITCZ (intertropical convergence zone): circulation pattern near equator where north and south Hadley cells meet
ITEP

ITEP-SAI Supernova Light Curve Catalogue: online catalog

ITEP-SAI Supernova Light Curve Catalogue: online catalog
iterative method

Krylov subspace method: efficient method of numerically solving sets of linear equations

ITM (Infrared Telescope Maffei): 80 cm infrared telescope in Antarctica
Itokawa

Hayabusa2: JAXA mission that returned a sample of an asteroid

ITU: international body coordinating communications technology
- extremely low frequency: electromagnetic radiation, frequency 3 Hz to 30 Hz
- super low frequency: electromagnetic radiation, frequency 30 Hz to 300 Hz
- ultra low frequency: electromagnetic radiation, frequency 300 Hz to 3 kHz
- very low frequency: electromagnetic radiation, frequency 3-30 kHz
IUCAA (Inter-University Centre for Astronomy and Astrophysics): initiative promoting astrophysics at Indian universities
IUE (International Ultraviolet Explorer): 1980s ultraviolet space telescope
IUE Data Analysis Center: see International Ultraviolet Explorer
IUEDAC: see International Ultraviolet Explorer
IUV: see MAVEN
IV

subgiant: slightly larger than normal star

IV Zw: see Catalog of Galaxies and Clusters of Galaxies
Ivanov: see rare designator prefixes
IVC: see high-velocity cloud
IWA (International Workshop for Astronomy): organization operating the IAYC
IWCA (International Workshop on Cometary Astronomy): occasional meeting
iWF-MAXI: see MAXI
Ixion

trans-Neptune object: minor planet beyond Neptune

IXO: see ROSAT
IXPE: space observatory with X-ray polarimeters

Index