Term Index (O)
- O:
- O-type star (O): star with spectral characteristics of above 30000 K
- Ohio Radio Survey (OSS): 1960s radio survey by Ohio State University
- oxygen (O): element, O, atomic number 8
- O star:
- O-type star (O): star with spectral characteristics of above 30000 K
- OΣ:
- OΣΣ:
- O-class:
- O-type star (O): star with spectral characteristics of above 30000 K
- O-class star:
- O-type star (O): star with spectral characteristics of above 30000 K
- O-type star (O): star with spectral characteristics of above 30000 K
- O1:
- LIGO: pair of observatories to detect gravitational waves
- O2:
- LIGO: pair of observatories to detect gravitational waves
- O3:
- LIGO: pair of observatories to detect gravitational waves
- O5:
- O5 spectral type (O5): spectral type of star with a temperature of about 45000 K
- O5 spectral type (O5): spectral type of star with a temperature of about 45000 K
- OAC:
- Astrocats: software to create and manage an astronomy catalog
- OAO:
- OAO-1:
- OAO-2:
- OAO-3:
- OAO-B:
- OASIS:
- OB association: stellar association with O or B class stars
- OB star: a hot star with class O or early B
- OB supergiant:
- Oberon:
- moon: a planet's natural satellite, such as Earth's
- Uranus: second outer-most solar system planet
- object:
- astronomical object: planet, star, galaxy, etc.
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- moon: a planet's natural satellite, such as Earth's
- object type:
- accretion disk: disk around an astronomical body of material that is accreting
- asteroid: minor planet without comet characteristics
- binary minor planet (BMP): minor planet with another body orbiting it
- binary SMBH (BSMBH,SMBBH,SMBHB): co-orbiting supermassive black holes
- black hole (BH): region of such high mass that light cannot escape
- bulge: denser group of stars within a larger group
- candidate companion (CC): possible object apparently orbiting a known object
- centaur: asteroid-like body orbiting among the outer planets
- circumplanetary disk: disk of dust and gas around a planet
- circumstellar disk: disk or ring shaped accumulation of matter around a star
- cloud: higher-density region of space
- comet: Sun-orbiting object with coma and possible tail
- compact object (CO): dense astronomical body such as white dwarf or denser
- damocloid: minor planet with a comet-like orbit
- dark nebula: cloud that obscures stars behind it
- decretion disk: disk around an astronomical body of its ejected material
- dwarf planet: round like a planet, only smaller
- emission nebula: nebula that emits light such as an HII region or PN
- filament: linear volume of high molecular gas density within a galaxy
- galaxy: gravitationally-bound group of stars
- galaxy cloud: substructure of a supercluster
- galaxy cluster (CL): large group of galaxies gravitationally-bound to the group
- globular cluster (GC): spherical group of stars orbiting a galaxy
- Herbig-Haro object (HH,HHO): illuminated nebula from colliding jets
- HI supershell: shells of HI hundreds of parsecs
- jet: stream of matter from an astronomical body
- Keplerian disk: disk whose motion follows Kepler's laws
- long-period comet: comet with an orbital period of more than 200 years
- MACHO: proposed astronomical objects comprising dark matter
- Mars crosser (MC,MCA): asteroid with an orbit that crosses that of Mars
- meteoroid: rocky object in solar system, smaller than an asteroid
- microquasar: stellar-sized black hole with quasar-like activity
- millisecond pulsar (MSP): pulsar spinning with a period in the range of milliseconds
- minor planet: lesser solar system body without comet characteristics
- moon: a planet's natural satellite, such as Earth's
- near-Earth object (NEO): object orbiting the Sun that passes close to Earth
- nebula: cloud of dust and gas
- oligarch: term for large planetesimals that dominate
- planet: round object orbiting a star that clears out its own orbital path
- planetary embryo: object that may grow into a future planet
- planetary mass object (PMO): has the mass of a planet
- planetary nebula (PN): gas shell ejected by a red giant
- planetesimal: objects held together by gravity that combine to form planets
- planetoid: an asteroid or physically similar body
- plutoid: Pluto-like dwarf planet
- point source: celestial object that focuses to a point or single Airy disk
- primordial black hole: black holes forming at the most dense volumes when inflation ceased
- protoplanet: simplest, least-developed object classified as a planet
- protoplanetary disk (PPD): disk of dust and gas around a young star or protostar
- protoplanetary nebula (PPN): short AGB phase before planetary nebula
- pseudobulge: like a galaxy bulge only flatter
- pulsar (PSR): type of astronomical body with EMR in regular cycles of seconds or less
- quasar (QSO): distant, bright object that appears something like a star
- radio source (RS): something in the sky generating radio signal
- RAMBO: proposed astronomical objects comprising dark matter
- reflection nebula: nebula made visible by light it scatters from nearby stars
- ring system: disk or set of rings orbiting a planet
- shell: hollow shaped region of some kind of ISM
- soft gamma repeater (SGR): object that produces repeated gamma ray bursts
- SSSB: solar system body smaller than a dwarf planet
- stellar stream: long group of co-moving stars
- stellar-mass black hole: black hole that is a stellar remnant
- subsatellite: object orbiting a moon
- supermassive black hole (SMBH): black hole with a mass of millions to billions of solar masses
- supernova remnant (SNR): nebula of debris resulting from a supernova
- supershell: very large ISM shell-shaped region
- telluric star: star of known spectrum used for calibration
- trans-Neptunian object (TNO): minor planet beyond Neptune
- transitional disk: disk with inner part cleared
- X-ray burster (XRB): neutron star binary producing nova-like bursts
- X-ray source: something in the sky generating X-ray signal
- objective lens:
- objects:
- oblateness:
- J2: geopotential coefficient regarding a planet's oblateness
- obliquity: angle between an object's rotational and orbital axes
- obscured fraction:
- obscured fraction-luminosity relation: relation between AGN luminosity and surrounding dust IR emission
- observable universe: that part of the universe that we can conceivably observe
- observation:
- band shifting: effect of redshift on photometry
- dropout: means of identifying distant galaxies
- field: adjective meaning "in this field of view but unrelated"
- striae: parallel ridges
- surface density (Σ): quantity such as mass per surface area
- synthetic field method (SFM): method of testing galaxy opacity
- telluric star: star of known spectrum used for calibration
- tracer: chemical whose presence indicates the presence of another chemical
- Observation Run 1:
- LIGO: pair of observatories to detect gravitational waves
- Observation Run 2:
- LIGO: pair of observatories to detect gravitational waves
- Observation Run 3:
- LIGO: pair of observatories to detect gravitational waves
- observational astronomy: term covering observation
- observatories:
- observatorio:
- Observatorio del Roque de los Muchachos:
- Observatorio del Teide:
- observatory: facility for astronomical observation
- observed color index:
- color index: a number that characterizes the color of an object
- observed wavelength:
- rest wavelength: normal wavelength observed when not moving in relation to the source
- observing program:
- OC:
- open cluster (OC): group of stars within a galaxy apparently formed by a single cloud
- occlusion:
- occultation: one celestial body hiding another from an observer
- occultation: one celestial body hiding another from an observer
- occultation observations: gathering astronomical information through measuring occultations
- occultation spectroscopy:
- occulter:
- coronagraph: telescope feature to block light from a specific body
- Exo-S: a study on the concept of a starshade mission
- New Worlds Mission: plan for space occulter to facilitate the view of exoplanets
- occulting bar: telescope feature to block light from a specific body
- starshade: spacecraft to block light from a specific body
- occulting bar: telescope feature to block light from a specific body
- ocean planet:
- ocean world:
- oceanic carbon cycle:
- Ocl:
- OCPP:
- octopole:
- octupole:
- octupole level:
- octupole term:
- ODE:
- ODI:
- Oe star:
- Be star: early star with Balmer emission lines
- OEC:
- OEFD:
- OEFP:
- off the shell:
- mass shell: conceptual volume of mass shaped like a hollow sphere
- off-axis telescope: telescope
- OGBD:
- OGLE: survey searching for microlensing transients
- OGLE-2005-BLG-3290Lb: exoplanet orbiting a binary star
- OGLE-2005-BLG-390L:
- OGS:
- HEAO-2: 1978 X-ray observatory space mission
- OH:
- hydroxyl (OH): neutral compound of hydrogen and oxygen, one atom each
- OH/IR source: AGB star with strong OH maser
- OH airglow:
- airglow: glow from a planet's atmosphere
- OH maser:
- OH/IR source: AGB star with strong OH maser
- OH/IR star:
- OHIO:
- Ohio Radio Survey (OSS): 1960s radio survey by Ohio State University
- Ohio Sky Survey:
- Ohio State University Radio Observatory:
- ohm:
- siemens (S): SI unit of electrical conductance
- ohm-meter:
- siemens (S): SI unit of electrical conductance
- Ohmic heating: heating resulting from an electric current through a material
- OHP 1.93 m:
- 51 Pegasi b (51 Peg b): first exoplanet found orbiting a main sequence star
- HD 189733 b: hot Jupiter orbiting an orange dwarf
- HD 209458 b: hot Jupiter discovered in 1999
- OHS:
- OIMS:
- OIR: a spectral "band name" for both visible light and infrared
- OL:
- Olbers' paradox: argument using the dark of the sky regarding the nature of the universe
- oligarch: term for large planetesimals that dominate
- oligarch theory:
- oligarchic accretion:
- oligarch: term for large planetesimals that dominate
- oligarchic growth:
- oligarch: term for large planetesimals that dominate
- olivine:
- methane (CH4): compound of one carbon and 4 hydrogen atoms
- Olympus Mons:
- Mars: well-explored planet in the solar system
- OM:
- XMM-Newton: X-ray observatory-satellite operated by ESA
- OMAG:
- OMC:
- OMEGA:
- Omega Centauri: large globular cluster
- Omega-Prime:
- OmegaCAM:
- OMM 1.6m:
- SIMP: 2000s infrared proper-motion survey
- on the shell:
- mass shell: conceptual volume of mass shaped like a hollow sphere
- On-Orbit Servicing:
- OSAM-1: prototype space robot for servicing satellites
- ONC:
- one dimensional climate model: atmospheric model ignoring all horizontal motion
- one dimensional model:
- one meter barrier:
- ONMS:
- Ontario:
- Oo:
- Oort Cloud: cloud of comets and minor planets around the solar system
- comet: Sun-orbiting object with coma and possible tail
- Oort constants: two constants characterizing local Milky-Way motion
- Ooty Radio Telescope (ORT): cylindrical radio telescope in India
- OPA:
- opacity (κ): a measure of opaqueness of a material
- OPE:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
- Open Astronomy Catalog:
- Astrocats: software to create and manage an astronomy catalog
- open cluster (OC): group of stars within a galaxy apparently formed by a single cloud
- open Dragone:
- open Dragone telescope:
- Open Exoplanet Catalogue (OEC): independently maintained list of known exoplanets
- Open Kilonova Catalog:
- Astrocats: software to create and manage an astronomy catalog
- open magnetic field lines:
- Open Supernova Catalog:
- Astrocats: software to create and manage an astronomy catalog
- Open TDE Catalog:
- open universe:
- open-Dragone design:
- OpenSpace: visualization software aimed at astrophysical data
- Oph-L 1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Ophelia:
- Ophiuchus Molecular Cloud:
- OPI:
- Opportunity:
- opposition: positioning of two astronomical objects 180 degrees apart in the sky
- optical:
- optical and infrared:
- OIR: a spectral "band name" for both visible light and infrared
- optical astronomy:
- optical axis: center line through an optical instrument
- optical coma:
- optical counterpart:
- counterpart: image found at same coordinates using different EMR
- optical depth (τ): a measure of opaqueness of a path of light
- optical depth to the EOR:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- optical double: double star where the two are not gravitationally bound
- optical fiber:
- Optical Gravitational Lensing Experiment:
- OGLE: survey searching for microlensing transients
- optical interferometer: interferometer of visible light
- optical interferometry:
- optical segmentation:
- optical SFR:
- optical star formation rate:
- optical telescope assembly:
- optical thickness:
- optical violent variable quasar:
- 3C 279: striking variable quasar
- optical window:
- optically thick:
- optically thin:
- optically violent variable quasar:
- blazar: very compact variable quasar
- optics: science and technology regarding visible light
- OPTIMOS:
- Optopus:
- ORAD:
- orange dwarf:
- K-type star (K): spectral class of star a bit cooler than the Sun
- red dwarf: small, cool main-sequence star
- orbit:
- orbit plot: graphic showing the path of an orbit as a line
- orbital:
- orbital element: parameters describing an orbit
- orbital inclination: angle between plane of an orbit and a reference plane
- minimum mass (m sin i): measured bound on the mass of an exoplanet
- orbital period: length of time for an orbiting object to complete one cycle
- mean anomaly: angle describing an object's position within an elliptical orbit
- period derivative: rate of change in the period of an orbit or rotation
- sidereal: relative to the fixed position of the stars
- synodic period: period until a planet returns to the same position relative to the Sun
- Orbital perturbation analysis:
- J2: geopotential coefficient regarding a planet's oblateness
- orbital plane:
- orbital plot:
- orbit plot: graphic showing the path of an orbit as a line
- orbital resonance: tendency of orbits of multiple bodies to remain in a simple pattern
- orbital speed: speed of an orbiting body around the barycenter of a system
- Orbiting Astronomical Observatory (OAO): series of 1960s-1970s NASA space telescopes
- Orbiting Solar Observatory 7:
- OSO 7: 1970s observatory-satellite for viewing the Sun
- Orbiting Wide-angle Light Collectors (OWL): planned space mission to detect cosmic rays through Earth atmosphere light flashes
- orbits:
- Orcus:
- order:
- order-of-magnitude:
- dex: a number or factor's log base 10
- orders-of-magnitude:
- dex: a number or factor's log base 10
- ordinary differential equation:
- ORFEUS SPAS:
- ORFEUS Telescope:
- ORFEUS-SPAS 1:
- ORFEUS-SPAS 2:
- organization:
- Origins Space Telescope (OST): concept for future very large space IR telescope
- Orion: well-known constellation in the northern hemisphere
- Orion A:
- Orion Arm:
- spiral arm: long, winding visible structure within a spiral galaxy
- Orion B:
- Orion Cluster:
- Orion Complex:
- Orion Disks: protoplanetary disks visible in front of Orion Nebula
- Orion Molecular Cloud Complex: group of molecular clouds with star forming regions
- Orion Molecular Clouds:
- Orion Nebula (M42, NGC 1976): easily observed nebula that includes SF regions
- Orion Nebula Cluster (ONC): open cluster in the constellation Orion
- Orion Spur:
- spiral arm: long, winding visible structure within a spiral galaxy
- Orion Trapezium Cluster:
- Orion variable:
- Orion-Cygnus Arm:
- spiral arm: long, winding visible structure within a spiral galaxy
- ORM:
- OROCHI:
- MMX: Japanese probe to bring back a sample of a Martian moon
- ORP:
- ORPA:
- orphan afterglow:
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- orphan GRB afterglow:
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Orphan stream: stellar stream wrapping around the Milky Way
- orrery: mechanical device to simulate the solar system
- ORT:
- orthogonal transfer CCD:
- OSAM-1: prototype space robot for servicing satellites
- OSC:
- Astrocats: software to create and manage an astronomy catalog
- OSCA:
- Oschin Schmidt:
- Oschin Telescope:
- oscillator strength: fraction expressing QM's contribution to the probability of absorption
- osculating orbit:
- OSIRIS:
- OSIRIS-REx: space mission aiming to return a sample of an asteroid
- OSO 7: 1970s observatory-satellite for viewing the Sun
- OSR:
- Tianwen-1 (TW-1): Mars rover launched in July 2020 and on its way
- OSS:
- OSSE:
- OSSOS:
- OST:
- OSURO:
- OTC:
- OTCCD:
- Other Worlds Laboratory (OWL): group researching planets and moons
- OTS:
- Oukaïmeden Observatory:
- TRAPPIST: ground-based automatic transiting planet finding telescope
- outer Lindblad resonance:
- Outer Solar System Origins Survey (OSSOS): survey searching for trans-Neptune objects
- outflow:
- outgassing:
- OUVS:
- overfitting:
- Overwhelmingly Large Telescope (OWL): 100 m telescope plan
- OVRO:
- OVRO 40 Meter Telescope:
- OVV:
- 3C 279: striking variable quasar
- OVV quasar:
- blazar: very compact variable quasar
- Owens Valley Long Wavelength Array:
- Owens Valley Radio Observatory (OVRO): group of radio telescopes in California near the VLBA
- OWL:
- Oxford SWIFT:
- oxidation:
- oxidation number:
- oxidation state: number of electrons loaned out by an atom in an ionic bond
- oxidation state: number of electrons loaned out by an atom in an ionic bond
- oxidation/reduction potential:
- oxidation/reduction reaction:
- oxide:
- geochemistry: the chemistry of the Earth, planets, and moons
- oxidizing agent:
- oxygen (O): element, O, atomic number 8
- oxygen burning: fusion reaction starting with oxygen
- oxygen lines: spectral lines specific to oxygen
- oxygen-burning shell:
- oxygen-neon-magnesium white dwarf:
- white dwarf (WD): stellar remnant of mostly electron degenerate matter
- oxygen-rich Wolf-Rayet:
- OzDES:
- ozone:
- earthshine: reflected and emitted electromagnetic radiation from Earth
- ozone layer:
Index