Term Index (R)
- R:
- R association:
- R band: band of visible light around 6500 angstroms
- R Coronae Borealis variable:
- R to the 1/4 law:
- Röntgensatellit:
- ROSAT: 1990s German space X-ray telescope
- r-process: synthesization of elements through neutron capture faster than beta decay
- r0:
- seeing: apparent blurring and twinkling of objects seen through atmosphere
- R200:
- R200c:
- R200m:
- R500:
- R500c:
- Re:
- RH:
- Holmberg radius (RH,RHO): a measure of size of galaxy based on surface brightness
- RHO:
- Holmberg radius (RH,RHO): a measure of size of galaxy based on surface brightness
- rL:
- Laplace radius (rL): a radius for a stable orbit of a satellite around a planet
- Rm:
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- Rsp:
- RA:
- RAC:
- Phoenix: Mars polar-region probe launched by NASA in 2007 with lander
- RAD:
- radar: probe based on reflecting radio waves
- Radcliffe Magellanic Clouds:
- Radcliffe Observatory:
- Radcliffe Observatory Magellanic Clouds Catalogue (RMC): catalog of stars in
- Radcliffe wave: wave-shaped string of molecular clouds
- radial:
- radial epicyclic frequency:
- radial mode:
- radial motion:
- radial quantum number:
- electron shell: radius-level around an atomic nucleus at which electrons can orbit
- radial velocimetry:
- radial velocity (RV): component of velocity toward or away from observer
- radial velocity method: method of detecting exoplanets and binary companions
- radial velocity observatory:
- radial-drift barrier: the problem that forming planets would drift inward into the star
- barrier: challenging issue regarding planet formation
- meter size barrier: a barrier to planet formation on the order of a meter diameter
- radian:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- radiance: measure of EMR to/from a solid angle through and area
- radiant:
- meteoroid: rocky object in solar system, smaller than an asteroid
- radiant exposure:
- flux: flow rate per unit area
- radiant flux: measure of brightness
- radiated excitation:
- radiation:
- radiation chemistry:
- radiolysis: similar to photodissociation from higher energy photons
- radiation detector:
- radiation driven implosion:
- radiation era: early universe era when radiation pressure dominated
- radiation flux:
- radiation hydrodynamics (RHD): hydrodynamics plus the effects of EMR
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- hydrodynamics: study of fluids in motion
- radiation magnetohydrodynamics:
- radiation pattern:
- radiation pressure: the pressure exerted by electromagnetic radiation
- radiation zone: region of a star transmitting energy through radiative diffusion
- radiation-dominated era:
- radiation era: early universe era when radiation pressure dominated
- radiative cooling timescale:
- timescale (t,τ): general length of time something takes
- radiative diffusion:
- radiation zone: region of a star transmitting energy through radiative diffusion
- radiative flux: power passing through a unit area
- radiative flux density:
- radiative forcing (RF): difference between a planet's incoming and outgoing radiation
- radiative timescale:
- timescale (t,τ): general length of time something takes
- radiative transfer (RT): energy transfer in the form of electromagnetic radiation
- radiative transfer code (RT code): computer model of a gas's radiative transfer
- radiative transfer equation:
- radiative transfer model (RTM): models of radiative transfer, often computerized
- radiative-convective climate model:
- radical:
- hydroxyl (OH): neutral compound of hydrogen and oxygen, one atom each
- radio: electromagnetic radiation, frequency 3kHz to 300GHz
- 1 Jansky Empty Field Survey (1 Jy): survey to find optical identifications for weak radio sources
- 1.3-mm observation: observation frequency useful for detecting dust
- 3C 273: first quasar discovered
- 3C 295: distant radio galaxy
- 3C 303: Seyfert galaxy
- 3C 327: elliptical radio galaxy
- 3C 48: radio galaxy/quasar
- 3C 9: first quasar discovered
- 87GB Catalog of Radio Sources (87GB): 1980s Green Bank radio survey
- Allen Telescope Array (ATA): array of radio telescopes in northern California for SETI
- antenna pattern: a radio telescope's pattern of directional sensitivity
- Arecibo Observatory (NAIC): large 305 m radio telescope in Puerto Rico
- Arecibo Occultation Survey (AO): 1960s radio survey using occultations by the Moon
- ASPECS: millimeter survey of HUDF
- ASTRON: Netherlands radio astronomy research organization
- Astronomical Image Processing System (AIPS): software for processing radio astronomy data
- Atacama Large Millimeter Array (ALMA): large radio telescope array in Chile
- Australia Telescope Compact Array (ATCA): radio telescope in eastern Australia
- Australia Telescope Large Area Survey (ATLAS): radio survey of two survey fields
- Australian Square Kilometre Array Pathfinder (ASKAP): radio telescope array of 36 12-meter dishes
- back end instrument: instruments of a telescope that process or combine signals
- Badgerys Creek Interferometer 101MHz Survey (Mills): early 1950s survey of southern-hemisphere radio sources
- beam: portion of a sky that a radio telescope is viewing
- Becker, White, and Edwards Catalog (BWE): 1990s radio catalog from a Green Bank 300ft Telescope survey
- Bologna Survey of Radio Sources: 1970s-1980s radio survey
- Cambridge Catalog of Radio Sources (C): series of catalogs of northern hemisphere sources
- Canadian Hydrogen Intensity Mapping Experiment (CHIME,CH): radio telescope mapping distant neutral hydrogen
- COMAP: high frequency radio telescope to map CO
- Combined Array for Research in Millimeter-wave Astronomy (CARMA): array of radio telescopes in eastern California
- commensal mode: telescope usage that accomplishes multiple observations simultaneously
- confusion limit: limit on telescope imaging due to too many sources in the same region
- Cosmic Anisotropy Telescope (CAT): 1990s interferometer to measure CMB variations
- Cosmic Lens All-sky Survey (CLASS): radio survey aimed at gravitational lenses
- CRATES: catalog of 8.4 GHz data on radio sources
- Cygnus A (3C 405,QSO B1957+405): early-discovered radio galaxy and quasar
- cylindrical telescope: telescope with cylindrical reflectors
- dispersion measure (DM): to what degree an EMR signal's lower frequencies are delayed
- Dominion Observatory 10.03 MHz Source Catalog (DB): 1960s survey of northern-hemisphere radio sources
- Dominion Observatory 1420 MHz Source Catalog (DA): 1960s survey of northern-hemisphere radio sources
- Dominion Radio Astrophysical Observatory (DRAO): radio observatory in British Columbia, Canada
- downconverter: device that reduces the frequency of a signal
- DSA-2000: array plan to detect radio transients
- Dwingeloo Obscured Galaxy Survey (DOGS): radio survey of ZOA for 21-cm lines indicating galaxies
- Earth-sized VLBI: ground-based VLBI with near-maximal baseline
- EBEX: balloon-based CMB polarization survey
- Effelsberg 100-m Radio Telescope: German large single-dish radio telescope
- electromagnetic spectrum: spectrum of EMR
- European Pulsar Timing Array (EPTA): European collaboration of radio telescopes
- European VLBI Network (EVN): consortium of radio telescopes to coordinate VLBI efforts
- Event Horizon Telescope (EHT): growing VLBI network
- Fanaroff-Riley classification: a classification of the radio characteristics of radio sources
- FAST: Arecibo-like 500 m telescope in deployment in China
- Fast Fourier Transform Telescope: proposed all-digital telescope with synthetic aperture
- fast radio burst (FRB,FRT): astronomical high energy radio pulses of a few milliseconds
- FIRST: 1990s radio survey
- flux density: measure of the strength of a radio signal
- focal plane array (FPA): array of receivers at the focus of a radio telescope
- Fourth Cambridge Catalog of Radio Sources (4C): 1960s catalog of northern hemisphere 178 MHz sources
- frequency modulation (FM): changing the frequency of a signal's carrier
- front end instrument: instruments of a telescope that detect and encode the signal
- Galactic Emission Mapping (GEM): radio sky survey
- Giant Metrewave Radio Telescope (GMRT): large radio interferometer in India
- Gould's Belt Distances Survey (GOBELINS): survey of parallax distances to Gould's Belt YSOs
- Green Bank 140 Foot Telescope: West Virginia radio telescope
- Green Bank 300ft Telescope (GB300): former large radio telescope at Green Bank
- Green Bank 6-cm Radio Source Catalog (GB6): catalog of from 1980s northern-hemisphere radio survey
- Green Bank Telescope (GBT,GB): West Virginia large radio telescope
- Greenland Telescope (GLT): 12 m radio telescope in Greenland
- GUPPI: radio-telescope back-end aimed at processing pulsar data
- HALCA: Japanese space radio telescope operating 1997-2005
- HERA: low frequency radio telescope
- HIRAX: radio telescope array 21-cm surveying
- Hydrogen Accretion in Local Galaxies Survey (HALOGAS): radio survey looking for HI in galaxy halos
- Institut de radioastronomie millimétrique (IRAM): organized radio astronomy collaboration between France, Germany, and Spain
- ionosphere: layers of Earth atmosphere with significant ions
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- jansky (Jy): unit of measurement of spectral flux density
- Jodrell Bank Observatory (JBO): radio observatory in England
- low frequency radio astronomy: astronomy using the lower end of the radio spectrum
- Low-frequency Array (LOFAR): low frequency radio telescope
- LSPE-STRIP: CMB survey telescope in Canary Islands
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- Mark II (MKII): 38 m radio telescope in England
- MeerKAT: new radio telescope in South Africa
- Meier paradox: mysterious decline in number of radio galaxy jets
- MERLIN: VLBI array spread across England
- microwave: electromagnetic radiation, frequency 300 MHz to 300 GHz
- MIGHTEE: radio survey of four established deep fields
- millimeter astronomy: observation and analysis at wavelengths on the order of a millimeter
- MOJAVE: program to monitor AGN jet radio brightness and polarization
- multichroic feedhorn array: radio array with sensors for two or more bands
- Murchison Widefield Array (MWA): low frequency radio telescope
- MUSTANG: bolometer array on the Green Bank Telescope
- Nançay Radio Telescope (NRT): France large single-dish radio telescope
- NANTEN2: millimeter telescope in Chile
- National Radio Astronomy Observatory (NRAO): US radio astronomy organization
- Next Generation Very Large Array (ngVLA): planned radio telescope array as a follow-on to ALMA and the Jansky VLA
- Northern Extended Millimeter Array (NOEMA): large radio telescope array under construction in Europe
- NRAO Catalog (NRAO): 1960s followup to Cambridge radio surveys
- Ohio Radio Survey (OSS): 1960s radio survey by Ohio State University
- Ooty Radio Telescope (ORT): cylindrical radio telescope in India
- Owens Valley Radio Observatory (OVRO): group of radio telescopes in California near the VLBA
- PALFA: Arecibo survey for pulsars
- PAPER: radio interferometer for 21-cm measurement
- Parkes Catalog (PKS): catalog of from 1960s-1990 of radio sources in southern hemisphere
- Parkes Multibeam Pulsar Survey (PMPS): late 1990s radio survey in search of pulsars
- Parkes Observatory: Australian large single-dish radio telescope
- Parkes Pulsar Timing Array (PPTA): group of pulsars timed by Parkes Observatory
- Parkes-MIT-NRAO Surveys (PMN): 1990 southern-hemisphere radio surveys
- phased array: method of using a set of antennas directionally
- plasma frequency: frequency of electron plasma oscillation
- pulsar timing array (PTA): cooperating set of pulsar timing observatories
- PUPPI: Arecibo radio-telescope instrument aimed at observing pulsars
- QMAP: mid 1990s balloon-based CMB survey
- quad-ridge flare horn (QRFH): type of horn that can be incorporated in radio telescope feeds
- Queen's University Radio Observatory (QRO): early radio astronomy facility near Kingston, Ontario
- radar: probe based on reflecting radio waves
- radio astronomy: astronomy observation and analysis of radio EMR
- radio frequency interference (RFI): transmissions in a frequency band under observation
- radio galaxy (RG): a galaxy emitting a lot of radio
- Radio Galaxy Zoo (RGZ): crowd-sourced classification of radio galaxies
- radio relics: clouds from past galaxy emitting radio synchrotron radiation
- radio source (RS): something in the sky generating radio signal
- radio source counts: using radio source population characteristics to determine curvature
- radio star: star emitting much radio
- radio telescope: telescope that operates in the radio frequency range of EMR
- radiometer equation: shows how long to observe a radio source
- RASS/Green Bank Catalog (RGB,RASSGB): combined list of radio galaxies from Rosat and Green Bank surveys
- RATAN-600: ring-shaped radio telescope in Russia
- RELIKT-1: instrument on 1980s Soviet satellite to view the CMB
- RMS astronomy: collective term for radio, millimeter, and submillimeter
- rotating radio transient (RRAT): radio bursts repeating sporadically
- Sardinia Radio Telescope (SRT): Italian large single-dish radio telescope
- Spektr-R: 10 m space radio telescope
- Square Kilometre Array (SKA): radio telescope collecting a square kilometer
- Strong Source Surveys: series of 1970s/1980s 5 GHz surveys
- Submillimeter Array (SMA): radio interferometer in Hawaii
- submillimeter astronomy: astronomy observation and analysis of borderline infrared EMR
- Texas Survey of Radio Sources at 365 MHz (TXS): 1970s/1970s radio survey made with the Texas Interferometer
- Third Cambridge Catalogue of Radio Sources (3C): 1959 catalog of northern hemisphere 159MHz sources
- TopHat: 2001 balloon -based CMB survey
- USS Sources: catalog of sources with steep spectral index
- UTMOST: telescope aiming to detect radio transients
- VERA: VLBI project to map the Milky Way
- Very Large Array (VLA): radio telescope in New Mexico
- Very Long Baseline Array (VLBA): radio interferometer stretching 8000 km
- Very Small Array (VSA): radio interferometer in Canary Islands
- very-long-baseline interferometry (VLBI): interferometry based upon storing timing data at each telescope
- Westerbork Synthesis Radio Telescope (WSRT): radio telescope array of 14 dishes in Netherlands
- Westerhout Radio Survey (W): 1950s radio survey of the galactic plane
- Yuan-Tseh Lee Array (YTLA,AMiBA): microwave interferometer in Canary Islands
- Radio Astronomical Telescope Academy Nauk 600:
- RATAN-600: ring-shaped radio telescope in Russia
- radio astronomy: astronomy observation and analysis of radio EMR
- integration time: time required to acquire signal
- radio: electromagnetic radiation, frequency 3kHz to 300GHz
- radio counterpart:
- counterpart: image found at same coordinates using different EMR
- radio frequency:
- radio frequency interference (RFI): transmissions in a frequency band under observation
- radio galaxy (RG): a galaxy emitting a lot of radio
- Radio Galaxy Zoo (RGZ): crowd-sourced classification of radio galaxies
- radio interferometry:
- radio loud:
- blazar: very compact variable quasar
- radio loud quasar:
- quasar (QSO): distant, bright object that appears something like a star
- radio millimeter submillimeter wavelength astronomy:
- RMS astronomy: collective term for radio, millimeter, and submillimeter
- radio quiet quasar:
- quasar (QSO): distant, bright object that appears something like a star
- radio quiet zone:
- radio relics: clouds from past galaxy emitting radio synchrotron radiation
- radio source (RS): something in the sky generating radio signal
- radio source counts: using radio source population characteristics to determine curvature
- radio source star:
- radio spectral index:
- spectral index (α): power by which an object's flux depends on frequency
- radio star: star emitting much radio
- radio telescope: telescope that operates in the radio frequency range of EMR
- radio transient:
- radio waves:
- radio: electromagnetic radiation, frequency 3kHz to 300GHz
- radio window:
- radio YSO:
- radio-loud:
- radio-loud blazar:
- radio-loud quasar:
- radio-quiet:
- radioactive dating: determining the age of a substance that has a radioactive component
- radioactive decay: changes in atomic nuclei that happen over time
- radioactive decay timescale:
- radioactive heating: a source of heat of some planets and moons
- radioactive isotope:
- isotope: subclass of an element with a specific number of nucleons
- radioactivity:
- RadioAstron:
- radiochemistry:
- radiolysis: similar to photodissociation from higher energy photons
- Radioisotope Heat Unit:
- MMRTG: power source for space probes
- radiolysis: similar to photodissociation from higher energy photons
- radiolytic chemistry:
- radiolysis: similar to photodissociation from higher energy photons
- radiometer: device for measuring radiant flux
- radiometer equation: shows how long to observe a radio source
- radiometric dating:
- radiometric noise:
- radiometry:
- radius:
- radius of stability:
- radius valley:
- Fulton gap: planets with radius 1.5 to 2 Earth radii are rare
- Radon transform:
- tomography: observation of sections of a 3D object
- RAFGL:
- Raleigh-Jeans approximation:
- Raleigh-Jeans limit:
- Raleigh-Jeans region:
- Ralph:
- ram pressure: pressure on a body moving through a fluid
- ram-pressure stripping:
- RAMBO: proposed astronomical objects comprising dark matter
- RAMSES: hydrodynamic simulation system
- random error:
- random forest: algorithmic method of developing decision trees
- random walk: movement with random turns
- radiation zone: region of a star transmitting energy through radiative diffusion
- rapid neutron-capture process:
- r-process: synthesization of elements through neutron capture faster than beta decay
- rapid proton-capture process:
- rp-process: synthesization of elements through proton capture
- rapid quenching:
- Rapid Telescopes For Optical Response:
- RAPTOR: automated array of telescopes to uncover and track transients
- rapid weathering:
- weathering: changes in surface due to contact with atmosphere
- RAPTOR: automated array of telescopes to uncover and track transients
- rare designator prefixes: designator prefixes generally used for only a few objects
- rare earth element:
- lanthanide (Ln): element with atomic numbers 57 through 71
- RASS:
- RASS/Green Bank Catalog (RGB,RASSGB): combined list of radio galaxies from Rosat and Green Bank surveys
- RASSGB:
- RAT:
- RATAN-600: ring-shaped radio telescope in Russia
- ratio:
- ratio of total to selective visual extinction:
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
- ray tracing:
- HARM²: technique for parallelizing computations of radiation with hydrodynamics
- Rayleigh criterion:
- angular resolution: measure of a telescope's ability to distinguish spatial detail
- apodization: improving telescope images by manipulating diffraction
- PSF fitting: untangling airy disks to gain effective resolution
- Rayleigh distribution:
- Rayleigh Jeans Law:
- Rayleigh scattering: wave scattering by particles smaller than the wavelength
- Rayleigh-Jeans law: yields approximation of black body curve useful at low frequencies
- Rayleigh-Jeans limit:
- Rayleigh-Jeans regime:
- Rayleigh-Taylor instability:
- RBS:
- RC:
- RC star:
- red clump (RC): like horizontal branch but at one temperature
- RC1:
- RC2:
- RC3:
- RCB:
- RCG:
- red clump (RC): like horizontal branch but at one temperature
- RCT:
- RD:
- dropout: means of identifying distant galaxies
- RDCS:
- ROSAT: 1990s German space X-ray telescope
- RDI:
- RDM:
- RDRS:
- RDS:
- ROSAT: 1990s German space X-ray telescope
- RE:
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- ROSAT: 1990s German space X-ray telescope
- Re-simulated Halo Sample for Statistics Observable-mass Distribution Study:
- RHAPSODY: simulation of galaxy cluster dark-matter halos
- REACT:
- reaction:
- reaction wheel:
- K2: second Kepler mission that worked around failed equipment
- Kepler Telescope: space telescope that watched stars for exoplanets
- REASON:
- recessional velocity:
- redshift (z): change to longer wavelengths due to Doppler effects
- recombination: time when the universe's ionized hydrogen atoms neutralized
- reconnection:
- reconnection sheet:
- current sheet: narrow sheet within a magnetic field where current flows
- RECONS: consortium for research on stars near the Sun
- recurrent nova:
- nova (N): white dwarf explosion
- red:
- globular cluster (GC): spherical group of stars orbiting a galaxy
- R band: band of visible light around 6500 angstroms
- red and dead: description of a galaxy with old stars and no star formation
- red clump (RC): like horizontal branch but at one temperature
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- red clump giant:
- red clump (RC): like horizontal branch but at one temperature
- red clump star:
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- red clump (RC): like horizontal branch but at one temperature
- red dropout galaxy:
- dropout: means of identifying distant galaxies
- red dwarf: small, cool main-sequence star
- red dwarfs:
- L-type star (L): spectral type of star cooler than an M-type star
- M dwarf: small, cool main-sequence star in stellar class M
- red edge:
- red galaxy:
- red giant: very bright red star
- red giant branch:
- red kilonova model:
- kilonova (KN): explosive event larger than a nova and smaller than a supernova
- red noise: noise tending toward lower frequencies
- Red Spot:
- red straggler:
- turn-off point (TO): point in H-R diagram of a cluster where stars turn red
- red supergiant:
- red supergiant cluster (RSGC): stellar cluster with multiple red supergiants
- red-giant branch (RGB): an early red-giant phase of post-main-sequence stellar evolution
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- redox:
- redox potential:
- redshift (z): change to longer wavelengths due to Doppler effects
- redshift parameter:
- redshift (z): change to longer wavelengths due to Doppler effects
- redshift space: concept of space using redshift as the radial dimension
- redshift space distortion:
- redshift survey: survey of the universe aiming at three dimensions
- redshift space: concept of space using redshift as the radial dimension
- redshift-angular size relation: how observed size depends on redshift
- redshift-magnitude relation: how apparent magnitude depends on redshift
- reduced mass: the reciprocal of the sum of the reciprocals of the masses of two objects
- reduced Planck constant:
- reducing agent:
- reducing atmosphere: atmosphere lacking oxygen or other oxidizers
- reduction:
- reduction potential (Eh,ORP,pE): measure of a chemical species' tendency to acquire electrons
- reference:
- bibcode: reference code for a journal article
- J designator: designator using equatorial coordinates at year 2000
- phone number: colloquial expression for coordinates
- Reference Catalogue of Bright Galaxies (RC,RC1): series of catalogs of nearby galaxies
- reference direction:
- reference plane:
- refined Bouguer correction:
- Bouguer anomaly: effect of terrain on gravity measurement on a planet's surface
- refined Bouguer reduction:
- Bouguer anomaly: effect of terrain on gravity measurement on a planet's surface
- reflecting telescope:
- reflection:
- earthshine: reflected and emitted electromagnetic radiation from Earth
- reflection nebula: nebula made visible by light it scatters from nearby stars
- reflection spectroscopy:
- reflector:
- reflector telescope: telescope using mirrors rather than lenses to magnify
- refraction:
- refractive index:
- refractive interstellar scintillation (RISS): refraction of star light by the ISM
- refractive scintillation:
- refractory:
- refractory compound:
- refractory element:
- refractory material: material with high condensation temperature
- regolith: loose solid material covering a planet's solid rock
- regolith scale:
- regolith: loose solid material covering a planet's solid rock
- regular moon:
- regular perturbation problem:
- regular satellite:
- reheating: theorized increase in temperature after cosmological inflation
- reionization:
- reionization epoch:
- Reissner-Nordström black hole:
- Reissner-Nordström metric:
- metric: mathematical generalization of the concept of distance
- Reissner-Nordström object:
- Related: boson:
- baryon: protons, neutrons, and other three-quark particles
- relation:
- relative astrometry:
- astrometry: precise measurement of the position and movement of stars
- relative atomic mass:
- element: class of atom based on its number of protons
- relative humidity:
- humidity: amount of water vapor in a portion of the atmosphere
- relative photometry:
- photometry: studying starlight through bandpass filters
- relativistic aberration:
- relativistic astrophysics: physics applicable to cosmology and strong field gravity
- relativistic beaming: directional relativistic effect on light from relativistic speeds
- relativistic effect: a substantial fraction of the speed of light
- relativistic energy: energy of an object including relativistic effects
- relativistic hydrodynamics:
- relativistic invariance: quantity that remains the same regardless of frame of reference
- relativistic jet:
- jet: stream of matter from an astronomical body
- relativistic Limber equation:
- relativistic magnetohydrodynamics:
- relativistic mass:
- mass: object's quality that determines the effects of forces and gravity
- relativistic momentum: momentum of an object including relativistic effects
- relativistic speed: a substantial fraction of the speed of light
- relativistic Sunyaev-Zel'dovich effect:
- relativity: physics models accommodating the constancy of the speed of light
- relaxation:
- relaxation time:
- Stokes number (Stk,St): measure of a particle's tendency to flow the flow of a fluid
- relic: particles left over from the events of the early universe
- freeze-out: particles existing long-term after a decoupling
- relic abundance:
- Big Bang nucleosynthesis (BBN): creation of atomic nuclei in the very early universe
- relic: particles left over from the events of the early universe
- relic neutrinos:
- RELIKT-1: instrument on 1980s Soviet satellite to view the CMB
- Rem:
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- REMS:
- Renson:
- repulsive dark matter (RDM): concept of dark matter that resists extreme dark-matter density
- Research Consortium On Nearby Stars:
- RECONS: consortium for research on stars near the Sun
- resistance:
- siemens (S): SI unit of electrical conductance
- resistance heating:
- Ohmic heating: heating resulting from an electric current through a material
- resistive MHD:
- resistivity:
- flux freezing: magnetic field lines becoming attached to plasma they pass through
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- siemens (S): SI unit of electrical conductance
- resolution:
- resolution convergence:
- resolved source:
- extended source: term for astronomical object producing EMR that can be focused
- point source: celestial object that focuses to a point or single Airy disk
- Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics:
- ROCKE-3D: Rocky-planet-oriented general circulation model
- resolving power:
- resonance:
- rest energy:
- rest frame:
- frame of reference: region, possibly in motion, from which something is observed/considered
- rest mass:
- mass: object's quality that determines the effects of forces and gravity
- relativistic energy: energy of an object including relativistic effects
- relativistic momentum: momentum of an object including relativistic effects
- rest wavelength: normal wavelength observed when not moving in relation to the source
- Restore-L:
- OSAM-1: prototype space robot for servicing satellites
- restricted circular three body problem:
- Reticulum:
- retrieval: determining measures through observation and modeling
- retrieval code:
- retrieval: determining measures through observation and modeling
- retrograde accreting black hole:
- retrograde accretion: accretion disk spinning in opposite direction to the body
- retrograde accretion disk:
- retrograde hot Jupiter: large hot planet orbiting opposite the expected direction
- retrograde motion:
- epicycle: small circular motion around a large circular motion
- retrograde orbit: orbit opposite the usual direction
- retrograde rotation:
- reverberation mapping:
- reversing layer:
- Review: 2019:
- Review: 2020:
- mass: object's quality that determines the effects of forces and gravity
- quark matter (QM): matter not made of protons and neutrons but of quarks
- Revised AFGL:
- Revised Luyten Half-second Catalog:
- Revised NGC:
- Revised NGC and IC:
- Revised Shapley-Ames Catalog:
- REX:
- Reynolds decomposition: mathematical separation of average and fluctuating parts of a quantity
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- Reynolds stress:
- RF:
- RFI:
- RG:
- RGB:
- RGB star:
- red-giant branch (RGB): an early red-giant phase of post-main-sequence stellar evolution
- RGS:
- XMM-Newton: X-ray observatory-satellite operated by ESA
- RGZ:
- RHAPSODY: simulation of galaxy cluster dark-matter halos
- RHAPSODY-G:
- RHAPSODY: simulation of galaxy cluster dark-matter halos
- RHCP:
- polarization: property of waves that oscillate in a particular direction
- RHD:
- Rhea:
- moon: a planet's natural satellite, such as Earth's
- Saturn: second largest planet in the solar system
- Rho Cassiopeiae:
- Rho Ophiuchi:
- Rho Ophiuchi Cloud Complex: nebula that is a nearby star-forming region
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- RHS:
- RHT:
- RHU:
- MMRTG: power source for space probes
- Ri:
- Richardson number (Ri): measure of fluid stability consisting of ratio of buoyancy and shear
- Richardson number (Ri): measure of fluid stability consisting of ratio of buoyancy and shear
- Riemann problem: consequence of discontinuities in numerical methods
- Rigel: brightest star in constellation Orion
- Orion: well-known constellation in the northern hemisphere
- right ascension (RA): direction coordinate along celestial equator
- right hand rule:
- right-hand circular polarization:
- polarization: property of waves that oscillate in a particular direction
- Rigil Kentaurus:
- RIMAS:
- RIME:
- JUICE: mission to Jupiter in development
- RIMFAX:
- Mars 2020: Mars rover in development for 2020 launch
- ring:
- ring galaxy: ring-like galaxy, darker in the middle
- ring singularity:
- ring system: disk or set of rings orbiting a planet
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- J1407: star orbited by a companion with a ring system
- Saturn: second largest planet in the solar system
- Uranus: second outer-most solar system planet
- ringdown:
- rings:
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- ring system: disk or set of rings orbiting a planet
- shepherd moon: small moon at outer edge of a ring
- ripper tines:
- CAESAR: planned space mission to return a sample of a comet
- rise azimuth:
- rise time:
- RISS:
- Ritchey-Chrétien telescope (RCT,RC): type of two-mirror reflector telescope
- RLOF:
- Roche limit: nearest a body can orbit another and survive
- RLQ:
- quasar (QSO): distant, bright object that appears something like a star
- RLS:
- RM:
- RM effect:
- RMC:
- RMHD:
- RMS: square root of the average of some squared values
- RMS astronomy: collective term for radio, millimeter, and submillimeter
- RMS astronomy: collective term for radio, millimeter, and submillimeter
- rms wavefront error:
- wavefront error (WFE): measure of a telescope's distortion of incoming waves
- RNGC:
- RNGC/IC:
- Ro:
- Rob:
- Robert C. Byrd Green Bank Telescope:
- Robertson-Walker metric:
- metric: mathematical generalization of the concept of distance
- Robertson-Walker scale factor:
- scale factor (a): relative size of the universe as a function of time
- RoboNet: global network of robotic telescopes to follow up on GRBs
- RoboNet-1.0:
- RoboNet: global network of robotic telescopes to follow up on GRBs
- RoboNet-II:
- RoboNet: global network of robotic telescopes to follow up on GRBs
- robotic fiber positioner:
- Robotic Optical Transient Search Experiment:
- ROTSE: automated array of telescopes to uncover and track transients
- robust association of massive baryonic objects:
- RAMBO: proposed astronomical objects comprising dark matter
- Roche limit: nearest a body can orbit another and survive
- Roche lobe:
- Roche limit: nearest a body can orbit another and survive
- Roche lobe overflow:
- Roche limit: nearest a body can orbit another and survive
- Roche radius:
- Roche limit: nearest a body can orbit another and survive
- rock:
- silicate: type of compound including silicon and oxygen
- rock vapor phase:
- ROCKE-3D: Rocky-planet-oriented general circulation model
- rocky planet: planet like Earth and Mars, mostly rock
- RODEO: code for 2D disk simulation
- ROE:
- Roe solver:
- RODEO: code for 2D disk simulation
- Roemer delay: timing differences in observed phenomenon due to Earth's position
- rogue planet:
- field: adjective meaning "in this field of view but unrelated"
- ROLIS:
- Rosetta: space probe that visited a comet
- rolling Hough transform:
- Roma-BZCAT: 2008 catalog of blazars
- Roman Space Telescope (RST,WFIRST): proposed near-infrared space observatory
- ROMAP:
- Rosetta: space probe that visited a comet
- Rome Observatory:
- root mean square:
- Roque de los Muchachos Observatory (ORM,LPO,NHO): observatory at La Palma in the Canary Islands
- Rosalind Franklin: Mars rover in development for 2020 launch
- ROSAT: 1990s German space X-ray telescope
- ROSAT All Sky Survey:
- Rosat All-sky Survey:
- Rosat Bright Survey (RBS): list of bright X-ray sources from ROSAT observations
- ROSAT Deep Cluster Survey:
- ROSAT: 1990s German space X-ray telescope
- ROSAT Deep Survey:
- deep survey: survey using lengthy observation to identify distant galaxies
- ROSAT: 1990s German space X-ray telescope
- Rosat Hard Survey (RHS): list of hard X-ray sources from ROSAT observations
- Roscosmos: Russian organization for space technology and research
- Roscosmos State Corporation for Space Activities:
- Roscosmos: Russian organization for space technology and research
- Rosetta: space probe that visited a comet
- ROSINA:
- Rosetta: space probe that visited a comet
- Ross:
- Ross 128 b:
- Ross 154: nearby red dwarf
- Ross 248: nearby red dwarf
- Rossby deformation radius:
- Rossby number (Ro): ratio of inertial to Coriolis force
- Rossby radius of deformation: length scale where rotation effects are significant
- Rossby wave instability (RWI): type of disk instability that may be a factor in planet formation
- Rossby waves: meandors in high-altitude winds
- Rosseland mean:
- Rosseland mean opacity: a useful weighted average of opacities at all the wavelengths
- Rosseland optical depth:
- Rossi X-ray Timing Explorer:
- RXTE: space mission to time X-ray variations
- Rossiter-McLaughlin effect (RM effect,RM): effect of transit on visible spectrum of the star
- rotating ellipsoidal variable:
- rotating radio transient (RRAT): radio bursts repeating sporadically
- rotating radio transit:
- rotating variable star:
- rotation:
- millisecond pulsar (MSP): pulsar spinning with a period in the range of milliseconds
- nutation: precession of a body's axis of rotation
- P-Pdot diagram: diagram comparing the rotation and the slowing of pulsars
- precession: periodic change in a body's rotation or orbit
- pulsar (PSR): type of astronomical body with EMR in regular cycles of seconds or less
- rotation curve: function mapping distance from galaxy center to orbital speed of stars
- rotation measure:
- Faraday rotation: rotation of optical polarization by a medium in a magnetic field
- rotation period: time it takes an astronomical body to revolve
- rotation rate:
- rotational broadening:
- rotational modulation:
- rotational velocity:
- ROTSE: automated array of telescopes to uncover and track transients
- ROTSE-I:
- ROTSE: automated array of telescopes to uncover and track transients
- ROTSE-II:
- ROTSE: automated array of telescopes to uncover and track transients
- ROTSE-III:
- ROTSE: automated array of telescopes to uncover and track transients
- ROX:
- Royal University of Edinburgh:
- rp-process: synthesization of elements through proton capture
- RPA:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
- RPC APXS:
- Rosetta: space probe that visited a comet
- RPI:
- IMAGE: satellite mission to study magnetosphere
- RPW:
- RPWI:
- JUICE: mission to Jupiter in development
- RPWS:
- Cassini: explorer spacecraft sent to Saturn
- RQQ:
- quasar (QSO): distant, bright object that appears something like a star
- RR:
- RR Lyrae:
- RR Lyrae star:
- RR Lyrae variable (RRL,RR): star with periodic variation often in globular clusters
- RRab:
- RRAT:
- RRc:
- RRd:
- RRL:
- RS:
- RS Canum Venaticorum star:
- RS Canum Venaticorum variable:
- RSA:
- RSD:
- redshift space: concept of space using redshift as the radial dimension
- RSG:
- RSGC:
- RSGCn:
- RSI:
- Rosetta: space probe that visited a comet
- RSR:
- RSS:
- RST:
- RSU:
- Rsun:
- Sun: star at center of solar system
- rSZ:
- rSZE:
- RT:
- RT code:
- RT instability: result of lighter fluid pushing a heavier fluid
- RTE:
- RTM:
- RTSW:
- Rubin Observatory (VRO,LSST): 8-meter survey reflector telescope under construction in Chile
- runaway accretion:
- accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- runaway greenhouse effect:
- greenhouse effect: mechanism that boosts temperature through selective blocking of EMR
- runaway growth:
- runaway process: a process with positive feedback so progress speeds progress
- runaway star:
- Russia:
- ExoMars: program to search for signs of life on Mars
- GRANAT: observatory-satellite for detecting gamma rays and X-rays
- Large Altazimuth Telescope (BTA-6): 6-meter reflector telescope in Russia
- RATAN-600: ring-shaped radio telescope in Russia
- Roscosmos: Russian organization for space technology and research
- Trace Gas Orbiter (TGO): ESA and Russian Mars orbiter-probe launched in 2016
- Russian:
- Spektr-R: 10 m space radio telescope
- Spektr-RG (SRG, SXG): Russian-German X-ray observatory launched in 2019
- Rutherford-Bohr model:
- Bohr model: has electrons circling nucleus in quantized orbits
- RV:
- RV method:
- 51 Pegasi b (51 Peg b): first exoplanet found orbiting a main sequence star
- 55 Cancri e (55 Cnc e): superearth orbiting a Sun-like star
- Automated Planet Finder (APF): robotic telescope to find exoplanets using RV method
- CRIRES: high resolution IR echelle spectrometer
- extra-solar planet: planet not in the solar system
- Gliese 436 b (GJ 436 b): hot Neptune found in 2004
- HARPS: high-precision spectrograph for exoplanet searches
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- HD 209458 b: hot Jupiter discovered in 1999
- HD 80606 b: hot Jupiter discovered in 2001
- HRS: high resolution spectrography
- Keck Planet Finder (KPF): spectrograph in development for Keck
- minimum mass (m sin i): measured bound on the mass of an exoplanet
- NGC 3201: globular cluster in which a black hole has been identified
- NIRPS: near-infrared extension to HARPS spectrograph
- PLATO: planned observatory-satellite aimed at finding exoplanets
- Proxima b: exoplanet orbiting Proxima Centauri
- radial velocity (RV): component of velocity toward or away from observer
- radial velocity method: method of detecting exoplanets and binary companions
- telluric line: absorption line in ground observation due to Earth atmosphere
- RV observatory:
- RV Tauri variable:
- RVS:
- Gaia: 2010s astrometry survey satellite
- RWI:
- RX:
- ROSAT: 1990s German space X-ray telescope
- RXC:
- ROSAT: 1990s German space X-ray telescope
- RXTE: space mission to time X-ray variations
- Rydberg constant:
- Balmer series (H): hydrogen lines for electrons settling from n > 2 to n = 2
- Brackett series: hydrogen lines for electrons settling from n > 4 to n = 4
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Paschen series: hydrogen lines for electrons settling from n > 3 to n = 3
Index