Term Index (U)

Astrophysics (Index)

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Term Index (U)

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

U1 UA UB UC UD UE UF UG UH UI UK UL UM UN UP UR US UT UU UV UW UX UZ

U: photometric filter for ultraviolet light
U: see Stokes parameters
U: see large quasar group
U: see rare designator prefixes
- UVJ diagram: diagram to identify star formation in distant galaxies
u (dalton): mass unit used on atomic scale
u: see u-v plane
u: see ugriz photometric system
U band (U): photometric filter for ultraviolet light
U filter: see U
U Geminorum variable: see dwarf nova
U Geminorum variable: see variable star
u': see ugriz photometric system
U-B: see color index
U-class spacecraft (CubeSat): type of small satellite built around a set of modular parts
U-Net: neural network software for image reconstruction
u-v plane: plane for displaying Fourier transforms of signal from the sky
- visibility: mathematical representation of interferometer's view
U1.27 (Huge-LQG): possible overly-large structure
UA: see Uppsala General Catalogue
UAE

Hope Probe: UAE Mars orbiter currently studying Mars

UAI (International Astronomical Union): association of professional astronomers
UARS (Upper Atmosphere Research Satellite): 1990s spacecraft to observe Earth ozone layer
UB: see rare designator prefixes
UBV: see rare designator prefixes
UBV M: see rare designator prefixes
UBV photometric system: commonly-cited photometric system for describing stars' colors
UBVI photometric system: see UBV photometric system
UBVRI photometric system: see UBV photometric system
ubvy98: see rare designator prefixes
UC Santa Cruz

Other Worlds Laboratory: initiative researching planets and moons

UCA (USNO Twin Astrograph): USNO astrograph deployed in 1970
UCAC (USNO CCD Astrograph Catalog): USNO star catalog including proper motions
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCAC-1: see USNO CCD Astrograph Catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCAC-2: see USNO CCD Astrograph Catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCAC-3: see USNO CCD Astrograph Catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCAC-4: see USNO CCD Astrograph Catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCAC-5: see USNO CCD Astrograph Catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
UCD: see dwarf galaxy classification
- dwarf galaxy: small galaxy with up to a few billion stars
UCHII: see HII region
UCL: see Scorpius-Centaurus Association
- UCLCHEM: code to simulate the chemical reactions due to heat
UCLCHEM: code to simulate the chemical reactions due to heat
UCLES: see Anglo-Australian Telescope
UCM: see rare designator prefixes
UCOMP: see Mauna Loa Solar Observatory
UCSD Cosmic X-ray Experiment: see OSO 7
UCSD Hard Solar X-ray Monitoring Instrument: see OSO 7
UDF: see Hubble Ultra-Deep Field
UDFj: see Hubble Ultra-Deep Field
UDFy: see Hubble Ultra-Deep Field
UDG (ultra diffuse galaxy): a galaxy with extremely low luminosity
- NGC 1052: elliptical galaxy with ultra diffuse dwarf satellites
UDS: see Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey
UDS: see UKIDSS
- FourStar Galaxy Evolution Survey: infrared deep-survey to detect galaxies
UDS field: see UKIDSS
UDXS: see UKIDSS
UESAC (Uppsala-ESO Survey of Asteroids and Comets): 1990s comet and asteroid survey
UF: "ultra faint"
UFD (ultra-faint dwarf galaxy): recently discovered faint dwarf galaxies in the Local Group
UFO (ultra-fast outflow): characteristic of some AGNs
UFO (unidentified flying object): reported but unexplained observation
UFT: see Theory of Everything
UFTI: see United Kingdom Infrared Telescope
UG: see dwarf nova
UG: see variable star
UG SS Cygni variable: see dwarf nova
UG SU Ursae Majoris: see dwarf nova
UG WZ Sagittae: see dwarf nova
UG Z Camelopardalis: see dwarf nova
UGC (Uppsala General Catalogue): 1973 catalog of galaxies visible from northern hemisphere
UGC 7654 (M87): supergiant elliptical galaxy in local universe
UGCA: see Uppsala General Catalogue
UGCG (Uppsala General Catalogue): 1973 catalog of galaxies visible from northern hemisphere
UGCS: see UKIDSS
UGP: see rare designator prefixes
UGPS: see UKIDSS
ugriz photometric system: photometric system used for SDSS
ugriz': see ugriz photometric system
UGSS: see dwarf nova
UGSU: see dwarf nova
UGWZ: see dwarf nova
UGZ: see dwarf nova
UH Hilo Hoku Ke'a: see Mauna Kea Observatories
- Mauna Kea: Hawaiian mountain, the site of observatories
UH88: see Mauna Kea Observatories
- Hawaii K-band Galaxy Survey: near-infrared survey of a selection of fields
- Mauna Kea: Hawaiian mountain, the site of observatories
- Nearby Supernova Factory: survey that scanned transient data for supernovae
UHE: see VHE
UHE cosmic rays: see cosmic rays
- CASA-MIA: 1990s cosmic-ray detector in Utah
- Pierre Auger Observatory: cosmic-ray observatory in Argentina
UHE gamma ray

VHE: 100 GeV or more

UHECR: see cosmic rays
- CASA-MIA: 1990s cosmic-ray detector in Utah
- Pierre Auger Observatory: cosmic-ray observatory in Argentina
UHEGR (ultra-high-energy gamma rays): energetic gamma rays with more than 100 TeV photon energy
- VHE: 100 GeV or more
UHRS: see Anglo-Australian Telescope
UHS: see rare designator prefixes
Uhuru: 1970 X-ray space telescope
UIST: see United Kingdom Infrared Telescope
UIT (Ultraviolet Imaging Telescope): 1990s ultraviolet space telescope used on two Space Shuttle missions
UK

Ariel 5: 1970s X-ray space telescope
British Astronomical Association: amateur astronomer organization
Engineering and Physical Sciences Research Council: UK agency for scientific research, including astronomy
Institute of Astronomy: Cambridge U astronomy research organization
Institute of Theoretical Astronomy: former Cambridge U astronomy research organization
Jodrell Bank Observatory: radio observatory in England
MERLIN: VLBI array spread across England
Monthly Notices of the Royal Astronomical Society: UK peer-reviewed astronomy research journal
Particle Physics and Astronomy Research Council: former UK science agency
RAS JobList: directory of astrophysics jobs
Royal Astronomy Society: UK society supporting and promoting astronomy
Royal Greenwich Observatory: former UK national observatory
Science and Engineering Research Council: old name of UK's EPSRC
Science and Technology Facilities Council, UK: UK research agency
Spaceguard Centre: UK private observatory dedicated to NEOs
UK Space Agency: UK government agency like NASA

UK Schmidt Southern Sky Survey (UK Schmidt Survey): photographic survey of the southern hemisphere sky
UK Schmidt Survey: photographic survey of the southern hemisphere sky
- Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
- APM Galaxy Survey: 1990s survey of galaxies in southern sky
- Arp-Madore Catalog of Southern Peculiar Galaxies: 1970s-1980s catalog from the UK Schmidt Survey
- Digitized Sky Survey: digitization of Palomar and UK Schmidt plates
UK Schmidt Telescope: 1.2 meter telescope in Australia with wide field-of-view
- APM Galaxy Survey: 1990s survey of galaxies in southern sky
- Duus-Newell catalog: list of southern galaxies/clusters assembled in 1970s
- Large Bright QSO Survey: 1980s quasar survey
- Siding Spring Observatory: observatory in New South Wales, Australia
- UK Schmidt Survey: photographic survey of the southern hemisphere sky
UK Space Agency: UK government agency like NASA
UKIDSS: five-part infrared survey using UKIRT
UKIRT (United Kingdom Infrared Telescope): Mauna Kea 3.8 meter infrared telescope
- Hawaii K-band Galaxy Survey: near-infrared survey of a selection of fields
- Mauna Kea: Hawaiian mountain, the site of observatories
- Mauna Kea Observatories: observatories on Mauna Kea in Hawaii
- UKIDSS: five-part infrared survey using UKIRT
- WFCAM Transit Survey: 2000s survey for exoplanet transits using UKIRT
UKIRT Infrared Deep Sky Survey (UKIDSS): five-part infrared survey using UKIRT
Ukranian

Bogolyubov Institute for Theoretical Physics: Ukrainian research institute

UKS: see UK Schmidt Telescope
UKSA (UK Space Agency): UK government agency like NASA
UKST (UK Schmidt Telescope): 1.2 meter telescope in Australia with wide field-of-view
- 6dF Galaxy Survey: UKST survey of galaxies in the southern sky
- Abell Catalog: galaxy cluster catalog assembled over 1950s-1980s
- APM Galaxy Survey: 1990s survey of galaxies in southern sky
- Catalog of Galaxies and Clusters of Galaxies: list of galaxies/clusters assembled in 1960s
- Duus-Newell catalog: list of southern galaxies/clusters assembled in 1970s
- Large Bright QSO Survey: 1980s quasar survey
- Siding Spring Observatory: observatory in New South Wales, Australia
- UK Schmidt Survey: photographic survey of the southern hemisphere sky
ULAS: see UKIDSS
ULDB: see GUSTO
ULEIS: see Advanced Composition Explorer
ULF (ultra low frequency): electromagnetic radiation, frequency 300 Hz to 3 kHz
ULIRG (ultraluminous infrared galaxy): a galaxy emitting a more far infrared than an LIRG
- luminous infrared galaxy: a galaxy emitting a lot of far-infrared light
Ultima Thule: see New Horizons
Ultimate Spitzer Phase Curve Survey: investigation of exoplanet atmospheres
Ultimate XSHOOTER legacy survey of quasars at z ~ 5.8 - 6.6 (XQR-30): ESO-VLT quasar survey
ULTIMATE-Subaru: see Subaru Telescope
ultra diffuse galaxy: a galaxy with extremely low luminosity
- NGC 1052: elliptical galaxy with ultra diffuse dwarf satellites
ultra low frequency: electromagnetic radiation, frequency 300 Hz to 3 kHz
ultra-compact dwarf galaxy: see dwarf galaxy classification
- dwarf galaxy: small galaxy with up to a few billion stars
ultra-cool dwarf (ultracool dwarf): star or brown dwarf cooler than M7 class
ultra-faint dwarf galaxy: recently discovered faint dwarf galaxies in the Local Group
ultra-fast outflow: characteristic of some AGNs
ultra-high energy cosmic rays: see cosmic rays
- CASA-MIA: 1990s cosmic-ray detector in Utah
ultra-high-energy: see VHE
ultra-high-energy gamma ray

VHE: 100 GeV or more

ultra-high-energy gamma rays: energetic gamma rays with more than 100 TeV photon energy
ultra-light axion: see axion
ultra-stripped SN: see core collapse supernova
ultra-stripped supernova: see core collapse supernova
ULTRACAM: see European Southern Observatory Very Large Telescope
ultracompact HII region: see HII region
ultracool dwarf: star or brown dwarf cooler than M7 class
- SPECULOOS: search for Earth-like exoplanets orbiting nearby dim stars
ultralight dark matter: see sub-GeV dark matter
ultralight repulsive dark matter: see repulsive dark matter
Ultralong-Duration Balloon: see GUSTO
ultraluminous infrared galaxy: a galaxy emitting a more far infrared than an LIRG
- luminous infrared galaxy: a galaxy emitting a lot of far-infrared light
ultraluminous X-ray source: X-ray source with luminosity between a star and an AGN
ultraluminous X-ray source: see X-ray source
ultrarelativistic: see relativistic speed
ultrarelativistic speed: see relativistic speed
ULTRASAT: future satellite to detect UV transients
ultraviolet: electromagnetic radiation, wavelength 10-400 nm
- Berkeley Extreme and Far-UV Spectrometer: 1990s UV spectrometer used on two Space Shuttle missions
- BUSS: 1970s balloon-based ultraviolet astronomy mission
- CHIPS: small satellite to investigate ISM plasma
- COLD GASS: survey of CO in nearby large galaxies
- CUTE: CubeSat ultraviolet space telescope
- electromagnetic spectrum: spectrum of EMR
- European Southern Observatory Very Large Telescope: four 8.2-meter optical telescopes in Chile that can act together
- extreme ultraviolet: electromagnetic radiation in the range of 10-124 nm
- Extreme Ultraviolet Explorer: 1990s ultraviolet space telescope
- Far Ultraviolet Spectroscopic Explorer: early 2000s space telescope for short-wavelength ultraviolet
- FAUST: 1990s ultraviolet space telescope used on two Space Shuttle missions
- Galaxy Evolution Explorer: observatory-satellite with 50-cm ultraviolet telescope
- HEASARC: NASA archive of data on high energy astronomy
- High Definition Space Telescope: proposed 12-meter space telescope
- High Energy Transient Explorer: 2000s space multi-band GRB observatory
- high-energy astrophysics: astronomy and physics of X-rays and gamma rays
- Hisaki: retired Japanese space ultraviolet telescope
- Hopkins Ultraviolet Telescope: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
- International Ultraviolet Explorer: 1980s ultraviolet space telescope
- Interstellar Medium Absorption Profile Spectrograph: 1980s/1990s UV spectrometer
- ionizing radiation: radiation with photon energy sufficient to ionize
- Kepler-Swift Active Galaxies and Stars Survey: X-ray/UV survey of objects within the Kepler field
- Kiso Survey of Ultraviolet Excess Galaxies: 1980 Japanese survey
- Large Binocular Telescope: dual 8.4 meter telescope in Arizona
- Lunar-based Ultraviolet Telescope: Chinese ultraviolet telescope on the Moon
- LUVOIR: plan for a space-based telescope
- Lyman-Werner photon: ultraviolet photon with proper energy to excite molecular hydrogen
- Markarian galaxy: list of galaxies with excess ultraviolet light
- Midcourse Space Experiment: 1990s space telescope
- MUSCLES: HST UV survey of some M Dwarfs that host exoplanets
- Orion space telescopes: two Russian 1970s UV space telescopes
- Palomar-Green Survey: list of objects with excess ultraviolet light
- SCAP: 1980s balloon-borne ultraviolet telescope
- Solar and Heliospheric Observatory: satellite observing the Sun
- Solar Maximum Mission: 1980s satellite to study the Sun during solar maximum
- STUDIO: balloon-borne 0.5 m ultraviolet telescope
- Swift: satellite for studying gamma-ray bursts
- TD-1A: 1970s European observatory-satellite with UV telescopes
- TRACE: former solar observing satellite
- Tubingen Ultraviolet Echelle Spectrometer: 1990s UV spectrometer used on two Space Shuttle missions
- U: photometric filter for ultraviolet light
- ULTRASAT: future satellite to detect UV transients
- ultraviolet astronomy: astronomy observation and analysis of UV
- Ultraviolet Hubble Ultra-deep Field: ultraviolet data covering the Hubble Ultra Deep Field region of the sky
- Ultraviolet Imaging Telescope: 1990s ultraviolet space telescope used on two Space Shuttle missions
- UVCANDELS: UV survey of CANDELS fields
- UVOIR: a spectral "band name" covering UV, visible light, and IR
- UVSC Pathfinder: instrument to observe the Sun
- VLT Survey Telescope: survey telescope located at the VLT site
- Wisconsin Ultraviolet Photo-polarimeter Experiment: 1990s ultraviolet space telescope used on two Shuttle Shuttle missions
- XEUV: electromagnetic radiation in the range of 0.15-124 nm
ultraviolet astronomy: astronomy observation and analysis of UV
ultraviolet catastrophe: see Rayleigh-Jeans law
Ultraviolet Coverage of the Panchromatic Hubble Ultra Deep Field (Ultraviolet Hubble Ultra-deep Field): ultraviolet data covering the Hubble Ultra Deep Field region of the sky
Ultraviolet Hubble Ultra-deep Field: ultraviolet data covering the Hubble Ultra Deep Field region of the sky
Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields (UVCANDELS): UV survey of CANDELS fields
Ultraviolet Imaging Telescope: 1990s ultraviolet space telescope used on two Space Shuttle missions
ultraviolet light (ultraviolet): electromagnetic radiation, wavelength 10-400 nm
ultraviolet source: see source
- radio source: astronomical object producing observable radio
- ultraviolet astronomy: astronomy observation and analysis of UV
UltraViolet Spectro-Coronagraph: see UVSC Pathfinder
UltraViolet Spectro-Coronagraph Pathfinder (UVSC Pathfinder): instrument to observe the Sun
Ultraviolet Transient Astronomy Satellite (ULTRASAT): future satellite to detect UV transients
UltraVISTA: near infrared survey using VISTA telescope
- VISTA: 4.1 meter telescope in Paranal Observatory in Chile
ULX (ultraluminous X-ray source): X-ray source with luminosity between a star and an AGN
ULX: see X-ray source
Ulysses: space mission to observe the Sun from off the ecliptic
UM: see rare designator prefixes
UMa: see rare designator prefixes
UMa II dSph (Ursa Major II Dwarf): dwarf spheroidal galaxy in the Local Group
umbrella sampling: method usable in MCMC that avoids some problems
Umbriel: see Uranus
- moon: a planet's natural satellite, such as Earth's
unbarred: see bar
unbarred galaxy

galaxy classification: morphological classification of galaxies

unbarred lenticular galaxy: see bar
unbarred spiral galaxy: see bar
unbound GMC: see giant molecular cloud
uncertainty principle (Heisenberg uncertainty principle): limit on observable position and momentum of an object
- electron degeneracy: electrons set free of atoms by the Pauli exclusion principle
- natural broadening: line broadening due to uncertainty principle
UNEX

CHIPS: small satellite to investigate ISM plasma

UNEX-1 (CHIPS): small satellite to investigate ISM plasma
UNH Solar Gamma-ray Monitor: see OSO 7
Uni-BRITE: see BRITE-Constellation
unidentified flying object: reported but unexplained observation
unified atomic mass unit (dalton): mass unit used on atomic scale
unified field theory: see Theory of Everything
unified model: single model explaining a number observed types of AGN
- broad line region: AGN region producing broader lines
- narrow line region: AGN region producing narrower lines
unified model of an AGN: see unified model
- broad line region: AGN region producing broader lines
- narrow line region: AGN region producing narrower lines
uniform theory of diffraction

diffraction: an effect of the edge of an obstacle on a wave

unit

angstrom: unit of length 10^-10 meters
arcsecond: a 3600th of an angular degree
astronomical unit: about 93 million miles
atm: unit of pressure
dalton: mass unit used on atomic scale
dex: a number or ratio's log base 10
electron volt: very small unit of energy
erg: CGS unit of energy
foe: unit of energy on the order of a supernova's output
Gal: gravimetry unit of the effect of a planet's gravity
gauss: measurement of magnetic field β
gigayear: a billion years
jansky: unit of measurement of spectral flux density
joule: SI unit of energy
kelvin: unit of temperature scale starting at absolute zero
light-year: distance that light travels in a year
Mega-Carrington: 10³⁴ ergs, a million times that of the Carrington Event
mole: unit roughly the count of hydrogen atoms in a gram
parsec: about 3.26 light-years
radian: angle/arc measurement equivalent to 180/π degrees
Rydberg unit: unit of energy near 13.6 eV
siemens: SI unit of electrical conductance
solar luminosity: luminosity unit representing the luminosity of the Sun
solar mass: mass unit representing the mass of the Sun
solar neutrino unit: unit for the detection rate of neutrino detectors
tesla: unit of magnetic flux density
torr: unit of pressure approximating a millimeter of mercury on Earth
watt: SI unit of power

unitarity bound: see Lee-Weinberg bound
United Arab Emirates

Hope Probe: UAE Mars orbiter currently studying Mars

United Kingdom Infrared Telescope: Mauna Kea 3.8 meter infrared telescope
United States Geological Survey: US government geological division
United States Naval Observatory (USNO): observatory obtaining astronomical data for Naval use
- Navy Precision Optical Interferometer: optical interferometer in Arizona
- NOMAD: astrometric star catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
- XZ Catalog of Zodiacal Stars: 1977 catalog of stars near the ecliptic
United States Naval Observatory Flagstaff Station: see USNO
- USNO Twin Astrograph: USNO astrograph deployed in 1970
United States Space Force: US space-related military organization
United States Space Surveillance Network: US survey-effort of space objects of interest
universal gas constant: see ideal gas law
universal gravitational constant (gravitational constant): indicates how much pull between two masses
universal time: see time standard
universe: see observable universe
Universities Space Research Association: university research collaboration
University College of London

UCLCHEM: code to simulate the chemical reactions due to heat

University of Bonn

Max Planck Institute for Radio Astronomy: Bonn research institute

University of California

Lick Observatory: California observatory of long standing

University of Cambridge

Kavli Institute: any of a number of science institutes supported by Kavli Foundation
Mullard Radio Astronomy Observatory: radio observatory near Cambridge, UK

University of Chicago

Kavli Institute: any of a number of science institutes supported by Kavli Foundation

University of Cologne

Max Planck Institute for Radio Astronomy: Bonn research institute

University of Hawaii

IRTF: Mauna Kea 3-meter infrared telescope
United Kingdom Infrared Telescope: Mauna Kea 3.8 meter infrared telescope

University of Hawaii Institute for Astronomy (Institute for Astronomy): U Hawaii astronomy research organization
- Mauna Kea Observatories: observatories on Mauna Kea in Hawaii
University of Heidelberg

Max Planck Institute for Astronomy: Heidelberg research institute

University of Texas Radio Astronomy Observatory

Texas Survey of Radio Sources at 365 MHz: 1970s/1980s radio survey made with the Texas Interferometer

University of Tokyo

Kavli Institute: any of a number of science institutes supported by Kavli Foundation

University of Tokyo Atacama Observatory: observatory for a 6.5 m infrared telescope under construction
University of Toronto

Canadian Institute for Theoretical Astrophysics: national research organization at University of Toronto
Dragonfly Telephoto Array: Canadian compact array of small visible-light telescopes

University of Tubingen

Tubingen Ultraviolet Echelle Spectrometer: 1990s UV spectrometer used on two Space Shuttle missions

University of Washington

Axion Dark Matter Experiment: a search for axions as potential dark matter particles

University-Class Explorer

CHIPS: small satellite to investigate ISM plasma

Uniview: planetarium software
unnormalized PDF: see probability density function
unnormalized PMF: see probability mass function
unresolved source (point source): celestial object that focuses to a point or single Airy disk
- extended source: term for astronomical object covering some area of the sky
- radio source: astronomical object producing observable radio
Unruh effect: see Hawking radiation
Unruh radiation: see Hawking radiation
unstable isotope: see isotope
unstable mass transfer: see mass transfer
unstable region (instability region): region around an object where orbits cannot persist
up: see flavor
up quark: see particle
up quark: see quark
- hyperon: exotic type of baryon
- standard model: model of elementary particles including quarks
Updated Zwicky Catalog: see Catalog of Galaxies and Clusters of Galaxies
- UZC-SSRS2 Group Catalog: 2002 catalog of galaxy groups
UPI: see SELENE
Upper Atmosphere Research Satellite: 1990s spacecraft to observe Earth ozone layer
Upper Centaurus-Lupus: see Scorpius-Centaurus Association
upper mass gap

intermediate-mass black hole: black hole between stellar mass and supermassive
pair-instability supernova: type of large supernova

upper meridian: see celestial meridian
upper meridian: see meridian
Upper Scorpius: see Scorpius-Centaurus Association
Upper Scorpius OB Association: see Scorpius-Centaurus Association
Upper-Scorpius OB Association

CTIO Upper-Scorpius OB Association Survey: survey of low-mass stars and brown dwarfs

Uppsala General Catalogue: 1973 catalog of galaxies visible from northern hemisphere
Uppsala General Catalogue of Galaxies (Uppsala General Catalogue): 1973 catalog of galaxies visible from northern hemisphere
Uppsala-ESO Survey of Asteroids and Comets: 1990s comet and asteroid survey
UPT: see double star designation
uranium

Earth: third solar system planet from the Sun

Uranometria: see Bayer designation
Uranus: second outer-most solar system planet
- giant planet: planet of more than 10 Earth masses
- ice giant: planet denser than gas planets and less than rocky planets
- Neptune: outer-most solar system planet
- 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
- Uranus Orbiter and Probe: concept for mission to Uranus
- Voyager: space probes to observe planets and the edge of the solar system
Uranus Orbiter and Probe: concept for mission to Uranus
URAP: see Ulysses
URAT: see USNO CCD Astrograph Catalog
URAT-1: see USNO CCD Astrograph Catalog
Urca process: neutrino-emitting process
Urca shell: see Urca process
Urca-process cooling: see Urca process
Urey: see Rosalind Franklin
Ursa Major Filament: see galaxy filament
Ursa Major I Dwarf

Milky Way subgroup: the Milky Way and its satellites

Ursa Major II Dwarf: dwarf spheroidal galaxy in the Local Group
- Milky Way subgroup: the Milky Way and its satellites
Ursa Minor Dwarf

Milky Way subgroup: the Milky Way and its satellites

US: see Scorpius-Centaurus Association
US: see rare designator prefixes
US Air Force

LINEAR: survey of near-Earth objects

US ELT Program: NOIRlab program supporting the TMT and GMT
US Navy

USNO: observatory obtaining astronomical data for Naval use

US Space Force (United States Space Force): US space-related military organization
- Ground-Base Electro-Optical Deep Space Surveillance: initiative to track artificial spacecraft including space junk
- LINEAR: survey of near-Earth objects
US-ELTP (US ELT Program): NOIRlab program supporting the TMT and GMT
USA: see ARGOS
- AAS Job Register: directory of astrophysics jobs
- Air Force Geophysics Laboratory: merged into the Air Force Research Laboratory (AFRL)
- Amateur Astronomers Association of New York: American organization
- American Astronomical Society: American organization
- American Geophysical Union: US organization
- American Meteor Society: meteor-science promotion organization
- American Museum of Natural History: NYC museum carrying out research including astrophysics
- American National Standards Institute: USA standards organization
- American Physical Society: American physics organization
- Astronomical Journal: American Astronomical Society journal
- Astrophysical Journal: American Astronomical Society scientific publication
- Astrophysical Journal Letters: American Astronomical Society scientific publication
- Astrophysical Journal Supplement Series: American Astronomical Society scientific publication
- Cape Canaveral Air Force Station: Air Force launch facilities adjacent to Kennedy Space Center
- Center for Advanced Space Studies: unit of Universities Space Research Association
- Center for Astrophysical Research in Antarctica: NSF science and technology center
- Center for Astrophysics and Space Sciences: UC San Diego academic institute
- decadal survey: type of once-a-decade planning report from NASA and the NAS
- Maui Optical Tracking and Identification Facility: USAF optical/infrared telescopes to Earth-orbiting objects
- Maui Space Surveillance Site: USAF observatory to track Earth-orbiting objects
- Midcourse Space Experiment: 1990s space telescope
- Multiyear Interactive Computer Almanac 1800-2050: ephemerides app created by USNO
- NASA: includes space-based astronomy research
- NASA Space Science Data Coordinated Archive: NASA archive of flight information and astronomy findings
- National Acadamy of Sciences: US organization of distinguished scientists
- National Academies of Sciences, Engineering, and Medicine: US collective of three national acadamies
- National Bureau of Standards: name of of NIST before 1988
- National Institute of Standards and Technology: US agency defining standards
- National Oceanic and Atmospheric Administration: US meteorology and oceanography agency
- National Optical Astronomy Observatory: previous name of US optical astronomy organization
- National Radio Astronomy Observatory: US radio astronomy organization
- National Science Foundation: US government organization funding scientific research
- National Solar Observatory: US government sponsored solar observatory
- Naval Research Laboratory: US Navy scientific research arm
- NOIRLab: US optical/infrared astronomy organization
- NSF AST: US government astronomical research funding division
- Planetary Science Institute: US research institution
- Publications of the Astronomical Society of the Pacific: monthly journal
- Santa Barbara Instrument Group: old name of Santa Barbara Scientific, telescope instrument manufacturer
- Snowmass: initiative recommending the next decade's particle physics strategy
- Society of Amateur Radio Astronomers: US organization
- Space Studies Board: National Academy of Sciences unit re astronomy an research via spacecraft
- Space Surveillance Telescope: 3.5-m US telescope to discover and monitor objects in space
- Space Telescope Science Institute: science operator of space telescopes
- United States Geological Survey: US government geological division
- United States Space Force: US space-related military organization
- United States Space Surveillance Network: US survey-effort of space objects of interest
- USNO: observatory obtaining astronomical data for Naval use
USco: see Scorpius-Centaurus Association
UScoCTIO (CTIO Upper-Scorpius OB Association Survey): survey of low-mass stars and brown dwarfs
USGC (UZC-SSRS2 Group Catalog): 2002 catalog of galaxy groups
USGS (United States Geological Survey): US government geological division
USNO: observatory obtaining astronomical data for Naval use
- Navy Precision Optical Interferometer: optical interferometer in Arizona
- NOMAD: astrometric star catalog
- USNO Twin Astrograph: USNO astrograph deployed in 1970
- XZ Catalog of Zodiacal Stars: 1977 catalog of stars near the ecliptic
USNO CCD Astrograph (USNO Twin Astrograph): USNO astrograph deployed in 1970
USNO CCD Astrograph Catalog: USNO star catalog including proper motions
- USNO Twin Astrograph: USNO astrograph deployed in 1970
USNO Robotic Astrometric Telescope: see USNO CCD Astrograph Catalog
USNO Twin Astrograph: USNO astrograph deployed in 1970
USNO-A: see USNO
- NOMAD: astrometric star catalog
USNO-B: see USNO
- NOMAD: astrometric star catalog
USO/RS: see Mars Global Surveyor
USPCS (Ultimate Spitzer Phase Curve Survey): investigation of exoplanet atmospheres
USRA (Universities Space Research Association): university research collaboration
USS: see rare designator prefixes
USS Sources: catalog of sources with steep spectral index
USSF (United States Space Force): US space-related military organization
USSN: see core collapse supernova
UT: see rare designator prefixes
UT: see time standard
UT1 Telescope: see European Southern Observatory Very Large Telescope
UT2 Telescope: see European Southern Observatory Very Large Telescope
UT3 Telescope: see European Southern Observatory Very Large Telescope
UT4 Telescope: see European Southern Observatory Very Large Telescope
Utah

CASA-MIA: 1990s cosmic-ray detector in Utah
Fly's Eye: 1980s cosmic-ray observatory
High Resolution Fly's Eye: 1990s-2000s cosmic-ray observatory
Telescope Array Project: cosmic-ray observatory aiming for extremely energetic particles

UTC

time standard: method of designating points in time and quantifying time periods

UTMOST: telescope aiming to detect radio transients
- MOST: radio telescope in New South Wales
UTMOST-2D: see UTMOST
- MOST: radio telescope in New South Wales
UTRAO

Texas Survey of Radio Sources at 365 MHz: 1970s/1980s radio survey made with the Texas Interferometer

UUDS: see UKIDSS
UV (ultraviolet): electromagnetic radiation, wavelength 10-400 nm
UV astronomy (ultraviolet astronomy): astronomy observation and analysis of UV
uv plane (u-v plane): plane for displaying Fourier transforms of signal from the sky
UV SFR: see star formation rate
UV source: see source
- radio source: astronomical object producing observable radio
- ultraviolet astronomy: astronomy observation and analysis of UV
UV star formation rate: see star formation rate
UV, optical, and infrared (UVOIR): a spectral "band name" covering UV, visible light, and IR
UV-Excess Survey of the Northern Galactic Plane: see IPHAS
UVA: see ultraviolet
UVB: see ultraviolet
uvby photometric system (Strömgren photometric system): four-color photometric system devised in 1950s
uvby system (Strömgren photometric system): four-color photometric system devised in 1950s
UVC: see ultraviolet
UVCANDELS: UV survey of CANDELS fields
UVCS: see Solar and Heliospheric Observatory
UVES: see European Southern Observatory Very Large Telescope
- integral field spectrograph: spectrograph that captures images
- integral field unit: instrument to allow a spectrograph to capture data over a 2D field
UVEX: see IPHAS
UVIS: see Cassini
UVIT: see AstroSat
UVJ diagram: diagram to identify star formation in distant galaxies
UVOIR: a spectral "band name" covering UV, visible light, and IR
UVOIR astronomy: see UVOIR
UVOT: see Swift
- Kepler-Swift Active Galaxies and Stars Survey: X-ray/UV survey of objects within the Kepler field
UVOTSSC1: see Swift
UVS: see Europa Clipper
UVS: see JUICE
UVS: see Juno
UVS: see Voyager
UVS/EUV: see Galileo
UVSC: see UVSC Pathfinder
UVSC Pathfinder: instrument to observe the Sun
UVSP: see Solar Maximum Mission
UVUDF (Ultraviolet Hubble Ultra-deep Field): ultraviolet data covering the Hubble Ultra Deep Field region of the sky
UWL: see Parkes Observatory
UX Orionis variable: see pre-main-sequence star
UXOR: see pre-main-sequence star
UZC: see Catalog of Galaxies and Clusters of Galaxies
- UZC-SSRS2 Group Catalog: 2002 catalog of galaxy groups
UZC-SSRS2 Group Catalog: 2002 catalog of galaxy groups

Index