Astronomy & Space Abbreviations
83 abbreviations · part of Science & Engineering Abbreviations
Abbreviations from astronomy, astrophysics and spaceflight: distance units such as AU, ly and pc, cosmology terms (CMB, dark matter, LCDM), classes of objects (AGN, NEO, KBO), telescopes and missions (JWST, HST, ALMA, TESS), orbits (LEO, GEO), space agencies and observatories, and the vocabulary of launches and spacewalks. Several, such as SETI, UFO and UAP, also appear regularly in general news coverage.
| Abbreviation | Stands for | Description |
|---|---|---|
| AGN | Active galactic nucleus | Compact region at the center of a galaxy that outshines all its stars, powered by gas spiraling into a supermassive black hole. |
| ALMA | Atacama Large Millimeter/submillimeter Array | Radio telescope of 66 high-precision antennas on the Chajnantor plateau in Chile, about 5,000 meters above sea level. |
| AU | Astronomical unit | Unit of distance roughly equal to the average distance between Earth and the Sun, fixed by the International Astronomical Union in 2012 at exactly 149,597,870,700… |
| BBN | Big Bang nucleosynthesis | Formation of the lightest atomic nuclei, deuterium, helium-3, helium-4 and a little lithium-7, during the first few minutes after the Big Bang. |
| BH | Black hole | Region of spacetime where gravity is so strong that nothing, not even light, can escape once it crosses the event horizon. |
| CMB | Cosmic microwave background | Faint microwave radiation filling the entire sky, the cooled afterglow of the hot early universe released about 380,000 years after the Big Bang. |
| CME | Coronal mass ejection | Huge eruption of magnetized plasma, often billions of tonnes, from the Sun's outer atmosphere into space. |
| CNSA | China National Space Administration | Chinese government agency responsible for civil space activities and international cooperation, established in 1993. |
| COBE | Cosmic Background Explorer | NASA satellite launched in 1989 that showed the cosmic microwave background has an almost perfect blackbody spectrum and detected its tiny temperature fluctuations, the… |
| CSM | Command and Service Module | Main spacecraft of the Apollo program: the cone-shaped command module housed the three-person crew and was the only part to return to Earth, while the cylindrical… |
| DART | Double Asteroid Redirection Test | NASA mission that deliberately crashed a spacecraft into the small asteroid moonlet Dimorphos on September 26, 2022, to test whether an impact could change an… |
| DE | Dark energy | Unknown form of energy that permeates space and drives the accelerating expansion of the universe, accounting for roughly 68% of its total energy content. |
| Dec | Declination | Celestial coordinate equivalent to latitude, measured in degrees north (+) or south (-) of the celestial equator. |
| delta-v | Change in velocity | Measure of how much a spacecraft can change its speed using its propulsion, the basic currency of mission planning. |
| DM | Dark matter | Invisible form of matter that does not emit, absorb or reflect light but reveals itself through gravity, holding galaxies and galaxy clusters together. |
| DSO | Deep-sky object | Amateur astronomy term for celestial objects beyond the solar system other than individual stars: galaxies, nebulae, star clusters and similar targets. |
| EDL | Entry, descent and landing | Phase of a planetary mission from reaching the top of the atmosphere to touching down, during which a spacecraft must slow from thousands of kilometers per hour to a… |
| EHT | Event Horizon Telescope | Global network of radio telescopes linked by very long baseline interferometry to form a virtual Earth-sized telescope. |
| ELT | Extremely Large Telescope | Optical and infrared telescope under construction by the European Southern Observatory on Cerro Armazones in Chile's Atacama Desert. |
| ESA | European Space Agency | Intergovernmental organization of more than 20 European countries that coordinates space research and exploration, including Earth observation, science missions… |
| ESO | European Southern Observatory | Intergovernmental astronomy organization founded in 1962 that operates world-class telescopes at La Silla, Paranal and Chajnantor in Chile's Atacama Desert. |
| ET | Extraterrestrial | Being, life form or object originating beyond Earth; in everyday use, an alien. |
| EVA | Extravehicular activity | Any activity by an astronaut outside a spacecraft, commonly called a spacewalk in orbit or a moonwalk on the lunar surface. |
| FAST | Five-hundred-meter Aperture Spherical radio Telescope | World's largest single-dish radio telescope, built into a natural limestone basin in Guizhou province, China, and completed in 2016. |
| FRB | Fast radio burst | Intense pulse of radio waves lasting a few milliseconds, arriving from distant galaxies. |
| GEO | Geostationary orbit | Circular orbit 35,786 kilometers above the equator in which a satellite circles Earth once per sidereal day, matching the planet's rotation so it appears fixed in the… |
| GRB | Gamma-ray burst | Brief, extremely energetic flash of gamma rays from a distant galaxy, lasting from milliseconds to minutes. |
| GTO | Geosynchronous transfer orbit | Elliptical orbit with a low point near Earth and a high point near 35,786 kilometers, used to move satellites from launch toward geostationary orbit. |
| H0 | Hubble constant | Present-day expansion rate of the universe, the speed at which galaxies recede per unit of distance, expressed in kilometers per second per megaparsec. |
| HEO | Highly elliptical orbit | Elongated orbit with a low perigee and a very high apogee, in which a satellite moves slowly near apogee and spends hours over one region. |
| HR diagram | Hertzsprung-Russell diagram | Scatter plot of stars by luminosity against surface temperature or color, the most important chart in stellar astronomy. |
| HST | Hubble Space Telescope | Space telescope with a 2.4-meter mirror, launched in 1990, that observes in ultraviolet, visible and near-infrared light from low Earth orbit. |
| HZ | Habitable zone | Range of distances from a star where a planet with an atmosphere could keep liquid water on its surface, neither too hot nor too cold, often called the Goldilocks zone. |
| IAU | International Astronomical Union | Worldwide organization of professional astronomers, founded in 1919, that is the recognized authority for naming celestial bodies and features and for defining… |
| ISRO | Indian Space Research Organisation | India's national space agency, founded in 1969 and headquartered in Bengaluru. |
| ISS | International Space Station | Crewed research laboratory orbiting Earth at about 400 kilometers, built and operated by the space agencies of the United States, Russia, Europe, Japan and Canada. |
| JAXA | Japan Aerospace Exploration Agency | Japan's national space agency, formed in 2003 by merging three earlier organizations. |
| JD | Julian date (Julian Day number) | A continuous count of days used in astronomy, starting at noon Universal Time on 1 January 4713 BC in the proleptic Julian calendar. |
| JPL | Jet Propulsion Laboratory | NASA research center in Southern California, managed by the California Institute of Technology, that builds and operates most of the agency's robotic planetary… |
| JWST | James Webb Space Telescope | Largest and most powerful space telescope ever launched, observing mainly in infrared light from an orbit around the Sun-Earth L2 point, 1.5 million kilometers from… |
| KBO | Kuiper belt object | Icy body orbiting in the Kuiper belt, a disk beyond Neptune extending roughly 30 to 50 astronomical units from the Sun. |
| kpc | Kiloparsec | One thousand parsecs, about 3,260 light-years, the natural unit for distances within galaxies. |
| LCDM | Lambda cold dark matter | Standard model of cosmology, also written Lambda-CDM, in which the universe is about 5% ordinary matter, 27% cold dark matter and 68% dark energy, represented by the… |
| LEM | Lunar Excursion Module | Two-stage spacecraft of the Apollo program that carried two astronauts from lunar orbit to the Moon's surface and back. |
| LEO | Low Earth orbit | Orbit up to about 2,000 kilometers above Earth's surface, where satellites circle the planet in roughly 90 to 127 minutes. |
| LISA | Laser Interferometer Space Antenna | Planned space-based gravitational-wave observatory led by the European Space Agency with NASA participation. |
| LOX | Liquid oxygen | Oxygen cooled to about -183 °C so it becomes a pale blue liquid, used as the oxidizer in most liquid-fueled rockets, paired with kerosene, liquid hydrogen or methane. |
| LSST | Legacy Survey of Space and Time | Ten-year survey of the southern sky by the Vera C. |
| ly | Light-year | Distance light travels in a vacuum in one Julian year, about 9.46 trillion kilometers (5.88 trillion miles). |
| M | Messier object | Prefix for objects in Charles Messier's catalogue of 110 nebulae, star clusters and galaxies, written as M plus a number, such as M31 for the Andromeda Galaxy, M42 for… |
| MACHO | Massive compact halo object | Proposed form of dark matter made of ordinary but faint bodies, such as black holes, neutron stars, brown dwarfs or rogue planets, in the halo of the Milky Way. |
| MECO | Main engine cutoff | Moment in a launch when a rocket stage's main engines shut down, usually just before stage separation. |
| MEO | Medium Earth orbit | Region between low Earth orbit and geostationary orbit, roughly 2,000 to 35,786 kilometers in altitude. |
| MOND | Modified Newtonian dynamics | Alternative to dark matter proposed by Mordehai Milgrom in 1983, in which gravity behaves differently at extremely low accelerations, around 10^-10 meters per second… |
| Mpc | Megaparsec | One million parsecs, about 3.26 million light-years, the standard unit for distances between galaxies and for the expansion rate of the universe. |
| NEA | Near-Earth asteroid | Asteroid in a near-Earth orbit, the large majority of near-Earth objects. |
| NEO | Near-Earth object | Asteroid or comet whose orbit brings it within 1.3 astronomical units of the Sun, and so potentially near Earth's orbit. |
| NGC | New General Catalogue | Catalogue of 7,840 nebulae, star clusters and galaxies compiled by John Louis Emil Dreyer and published in 1888. |
| NS | Neutron star | Collapsed core of a massive star after a supernova, packing more than the Sun's mass into a sphere about 20 kilometers across. |
| pc | Parsec | Astronomical unit of distance equal to about 3.26 light-years or 206,265 astronomical units. |
| PHA | Potentially hazardous asteroid | Near-Earth asteroid whose orbit comes within 0.05 astronomical units (about 7.5 million kilometers) of Earth's and that is large enough, roughly 140 meters or more, to… |
| QSO | Quasi-stellar object | Extremely luminous active galactic nucleus that appears star-like in telescopes because it is so distant; quasars are powered by matter falling into black holes of… |
| RA | Right ascension | Celestial coordinate equivalent to longitude, measured eastward along the celestial equator from the point of the March equinox, in hours, minutes and seconds from 0 to… |
| RP-1 | Rocket Propellant-1 | Highly refined kerosene used as rocket fuel with liquid oxygen, prized for being dense, storable at room temperature and relatively cheap. |
| RTG | Radioisotope thermoelectric generator | Power source that converts heat from the radioactive decay of plutonium-238 into electricity using thermocouples, with no moving parts. |
| SETI | Search for extraterrestrial intelligence | Scientific effort to detect evidence of technological civilizations beyond Earth, mainly by listening for artificial radio signals and, more recently, laser flashes and… |
| SKA | Square Kilometre Array | International radio telescope project under construction at two sites: low-frequency antennas in Western Australia and mid-frequency dishes in South Africa's Karoo… |
| SLS | Space Launch System | NASA's super heavy-lift rocket developed to send Orion crew capsules to the Moon under the Artemis program. |
| SMBH | Supermassive black hole | Black hole with a mass from about a hundred thousand to billions of times the Sun's, found at the centers of most large galaxies. |
| SN | Supernova | Powerful stellar explosion that can briefly outshine an entire galaxy. |
| SOHO | Solar and Heliospheric Observatory | Joint ESA-NASA spacecraft launched in December 1995 that watches the Sun from the L1 point, 1.5 million kilometers toward the Sun. |
| SRB | Solid rocket booster | Rocket motor filled with solid propellant, strapped to a launch vehicle to add thrust during the first minutes of flight. |
| SSO | Sun-synchronous orbit | Nearly polar orbit, typically 600 to 800 kilometers high, whose plane rotates about one degree per day so a satellite passes over any given spot at the same local solar… |
| TESS | Transiting Exoplanet Survey Satellite | NASA space telescope launched in April 2018 that surveys nearly the whole sky for planets passing in front of bright, nearby stars. |
| TLI | Trans-lunar injection | Engine burn that accelerates a spacecraft from Earth orbit onto a trajectory toward the Moon, adding about 3 kilometers per second of velocity. |
| TNO | Trans-Neptunian object | Any solar system body that orbits the Sun at a greater average distance than Neptune. |
| UAP | Unidentified anomalous phenomena | US government term for observations in the air, space or sea that cannot be immediately identified, replacing the stigma-laden UFO in official reports. |
| UFO | Unidentified flying object | Anything seen in the sky that an observer cannot identify, popularly associated with alien spacecraft. |
| VLA | Very Large Array | Radio observatory of 27 antennas, each 25 meters across, arranged in a Y shape on the Plains of San Agustin in New Mexico. |
| VLT | Very Large Telescope | Array of four 8.2-meter telescopes, plus smaller auxiliary telescopes, operated by the European Southern Observatory on Cerro Paranal in northern Chile. |
| WD | White dwarf | Dense, Earth-sized remnant left when a star like the Sun runs out of fuel and sheds its outer layers. |
| WIMP | Weakly interacting massive particle | Hypothetical dark matter particle that would interact through gravity and possibly the weak nuclear force, with a mass similar to or larger than a proton's. |
| WMAP | Wilkinson Microwave Anisotropy Probe | NASA spacecraft that mapped temperature differences in the cosmic microwave background from 2001 to 2010. |
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