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
- UCA (USNO Twin Astrograph): USNO astrograph deployed in 1970
- UCAC (USNO CCD Astrograph Catalog): USNO star catalog including proper motions
- UCAC-1: see USNO CCD Astrograph Catalog
- UCAC-2: see USNO CCD Astrograph Catalog
- UCAC-3: see USNO CCD Astrograph Catalog
- UCAC-4: see USNO CCD Astrograph Catalog
- UCAC-5: see USNO CCD Astrograph Catalog
- UCD: see dwarf galaxy classification
- 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 High Altitude 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
- 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
- UHE: see VHE
- UHE cosmic rays: see cosmic rays
- UHE gamma ray
- UHECR: see cosmic rays
- UHEGR (ultra-high-energy gamma rays): energetic gamma rays with more than 100 TeV photon energy
- 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
- 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
- UK Schmidt Telescope: 1.2 meter telescope in Australia with wide field-of-view
- 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
- UKIRT Infrared Deep Sky Survey (UKIDSS): five-part infrared survey using UKIRT
- Ukranian
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- United States Naval Observatory Flagstaff Station: see USNO
- 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
- University of California
- University of Cambridge
- University of Chicago
- Kavli Institute: any of a number of science institutes supported by Kavli Foundation
- University of Cologne
- University of Hawaii
- University of Hawaii Institute for Astronomy (Institute for Astronomy): U Hawaii astronomy research organization
- University of Heidelberg
- University of Texas Radio Astronomy Observatory
- 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
- University of Tubingen
- University of Washington
- 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
- Updated Zwicky Catalog: see Catalog of Galaxies and Clusters of Galaxies
- UPI: see SELENE
- Upper Atmosphere Research Satellite: 1990s spacecraft to observe Earth ozone layer
- Upper Centaurus-Lupus: see Scorpius-Centaurus Association
- upper mass gap
- 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
- 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
- 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
- Ursa Major II Dwarf: dwarf spheroidal galaxy in the Local Group
- Ursa Minor Dwarf
- 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
- US-ELTP (US ELT Program): NOIRlab program supporting the TMT and GMT
- USA: see ARGOS
- 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
- USNO CCD Astrograph (USNO Twin Astrograph): USNO astrograph deployed in 1970
- USNO CCD Astrograph Catalog: USNO star catalog including proper motions
- 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
- 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
- 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
- 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
- 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
- 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
Index