Term Index (L)
- L:
- L band:
- infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- L dwarf:
- brown dwarf (BD): star-like object with less mass than a star
- L-type star (L): type of star cooler than an M-type star
- L'Institute Canadian d'astrophysique théorique:
- L-class:
- L-type star (L): type of star cooler than an M-type star
- L-point:
- L-type star (L): type of star cooler than an M-type star
- L1:
- L1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- L2:
- ARIEL: planned space mission for exoplanet spectrography
- Darwin: past plan for space telescopes acting as an interferometer
- eROSITA: future space X-ray telescope
- Euclid: planned observatory-satellite to measure dark energy
- FINESSE: planned space mission for exoplanet spectrography
- Gaia: survey satellite at 400-1000 nanometers
- HabEx: proposed space mission to directly image exoplanets
- Herschel Space Observatory: infrared observatory-satellite with 3.5 meter reflector
- High Definition Space Telescope (HDST): proposed 12m space telescope
- Hill radius: radius of gravitational influence of a body
- James Webb Space Telescope (JWST): future space-based 6.5 meter infrared telescope
- Lagrangian point: points around two orbiting bodies where small objects sit
- LiteBIRD: proposed spacecraft to map CMB polarization
- LUVOIR: plan for a space-based 10 meter telescope
- Origins Space Telescope (OST): concept for future very large space IR telescope
- Planck: microwave telescope in space
- PLATO: planned observatory-satellite aimed at finding exoplanets
- SPICA: plan for a future space IR telescope
- WFIRST: proposed space observatory
- Wilkinson Microwave Anisotropy Probe (WMAP): spacecraft that measured variations in the cosmic background radiation
- L3:
- L4:
- L5:
- L500:
- LBol:
- LIR:
- infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- Lsun:
- watt (W): SI unit of power
- La Silla Observatory:
- LABOCA:
- LABOCA ECDFS Submillimeter Survey:
- LABOCA ECDFS Submm Survey:
- LABOCA Extended Deep Field South Submillimetre Survey (LESS): submillimeter survey of a well-studied piece of sky
- Lac:
- Lac 9352:
- Lacaille:
- Lacaille 9352: red dwarf that is the tenth nearest star system
- Lacaille Star Catalog (Lac): 1700s catalog of about 10,000 southern hemisphere stars
- LAE:
- Laevens 2:
- Lagrange point:
- Lagrange stability: a quality of some stable orbits
- Lagrangian code:
- Lagrangian libration point:
- Lagrangian point: points around two orbiting bodies where small objects sit
- Lalande 21185: nearby red dwarf
- LAMBDA: NASA archive center re CMB data
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- laminar flow:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LAMOST Experiment for Galactic Understanding and Evolution:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LAMP:
- Landau-Oppenheimer-Volkoff limit:
- Lane-Emden equation: form of equation of state for gas ball in hydrostatic equilibrium
- Laniakea:
- Laniakea Supercluster: group of clusters including the Local Group
- lanthanide (Ln): element with atomic numbers 57 through 71
- lanthanum:
- lanthanide (Ln): element with atomic numbers 57 through 71
- Laplace radius (rL): a radius for a stable orbit of a satellite around a planet
- Laplace spherical harmonics:
- Laplace's equation:
- Laplace-Lagrange secular evolution theory:
- Laplace-Lagrange secular theory: theory of evolution of planetary orbits
- Large Altazimuth Telescope (BTA-6): 6 meter reflector telescope in Russia
- Large Binocular Telescope (LBT): dual 8.4 meter telescope in Arizona
- Large Binocular Telescope Interferometer:
- Large Bright QSO Survey (LBQS): 1980s quasar survey
- Large Magellanic Cloud (LMC): irregular satellite galaxy of the Milky Way
- Large Millimeter Telescope (LMT): large microwave telescope in Mexico
- TolTEC: Sensitive infrared camera under construction for the LMT
- large quasar group (LQG): structure consisting of a collection of quasars
- Large Scale Cryogenic Gravitational Wave Telescope:
- KAGRA: pair of interferometers to detect gravitational waves
- large scale streaming motion:
- large scale structure (LSS): the universe's structure as in placement of clusters
- large scale structure of the universe:
- large scale structures:
- galaxy bias: degree to which galaxy density fails to correspond to dark matter density
- supercluster: cluster of galaxy clusters
- void: empty spaces between large scale structures
- Large Sky Area Multi-object Fibre Spectroscopic Telescope:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- Large Strategic Science Mission:
- Lynx: concept for space X-ray observatory
- Large Strategic Science Missions:
- NASA: includes space-based astronomy research
- Large Synoptic Survey Telescope (LSST): 8-meter survey reflecting telescope under construction in Chile
- Large UV/Optical/Infrared Surveyor:
- LUVOIR: plan for a space-based 10 meter telescope
- Large Zenith Telescope (LZT): 6 meter liquid mirror telescope in British Columbia
- LAS:
- UKIDSS: five-part infrared survey using UKIRT
- Las Campanas Observatory:
- Las Cumbres Observatory (LCO): world-wide network of telescopes
- LASCO:
- LasDamas: simulations of large scale evolution of dark matter and galaxies
- laser:
- coherent light: beam of light at a single frequency
- emission: addition of photons to a beam of EMR
- Virgo: ground-based gravitational-wave detector in Italy
- Laser Interferometer Gravitational-wave Observatory:
- LIGO: pair of observatories to detect gravitational waves
- Laser Interferometer Space Antenna:
- LISA: proposed space mission to detect gravitational waves
- LASS:
- HEAO-1: 1977 X-ray observatory space mission
- last parsec problem:
- LAT:
- Fermi (FGST,GLAST): satellite for studying gamma rays
- LAT All-sky Survey:
- Fermi (FGST,GLAST): satellite for studying gamma rays
- late:
- late heavy bombardment (LHB): time after solar system planet-formation when many impacts occurred
- late-type galaxy:
- galaxy: gravitationally-bound group of stars
- late-type star:
- latent heat:
- latitude:
- law of cosmic censorship: a singularity cannot be observed
- law of gravitation:
- law of refraction:
- Lawrence Lowell Telescope:
- LBC:
- LBG:
- LBN:
- LBQS:
- LBT:
- LBTI:
- LBTI/LMIRCAM:
- LBTI/NOMIC:
- LC:
- LCDM:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- LCGT:
- KAGRA: pair of interferometers to detect gravitational waves
- LCL:
- LCO:
- LCROSS: space probe observing the lunar poles
- LDN:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- LDSS3:
- leakage neutron:
- LECP:
- Voyager: space probes to observe planets and the edge of the solar system
- LEDA:
- left-hand circular polarization:
- polarization: property of waves that oscillate in a particular direction
- Legacy Archive for Microwave Background Data Analysis:
- LAMBDA: NASA archive center re CMB data
- Legendre polynomials: useful sequence of polynomials
- Lego principle: principle that life is associated with a skew in molecule abundances
- LEGUE:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- LEND:
- length contraction:
- lensing deflection field:
- lensing map:
- lenslet array:
- lensmaker's equation:
- lensmaker's formula:
- lenticular galaxy:
- Leo Cluster:
- lepton:
- baryon: protons, neutrons, and other three-quark particles
- particle: very small thing
- LESS:
- LETGS:
- Levy Spectrometer:
- LF:
- luminosity function (LF): function giving number of stars or galaxies at different luminosities
- LF radio astronomy:
- LFAA:
- LFC:
- LFI:
- Planck: microwave telescope in space
- LFT:
- LG:
- Local Group (LG): group of galaxies including the Milky Way
- LGM-1:
- pulsar (PSR): astronomical body whose electromagnetic radiation displays a cycle
- LGRB:
- LHB:
- LHCP:
- polarization: property of waves that oscillate in a particular direction
- LHO:
- LIGO: pair of observatories to detect gravitational waves
- LHS:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- LHS 1140b:
- LHS 1140: red dwarf with rocky planet in its habitable zone
- Li:
- lithium (Li): metal, Li, atomic number 3
- libration: oscillating motion of orbiting bodies relative to each other
- libration in latitude:
- libration: oscillating motion of orbiting bodies relative to each other
- libration in longitude:
- libration: oscillating motion of orbiting bodies relative to each other
- libration point:
- Lagrangian point: points around two orbiting bodies where small objects sit
- libration: oscillating motion of orbiting bodies relative to each other
- Lick 3m:
- Lick Observatory:
- Lick Observatory and Tenegra Observatory Supernova Searches:
- Lick Observatory Calcium Line Survey (LkCl): 1980s survey of T-Tauri stars in the Taurus-Auriga Complex
- Lick Observatory Supernova Search (LOSS): search for supernovae for cosmological study
- LIDAR:
- MMX: Japanese probe to bring back a sample of a Martian moon
- Lidov-Kozai effect:
- Kozai mechanism: an effect on an orbit by another, more distant orbiting body
- Lidov-Kozai mechanism:
- Kozai mechanism: an effect on an orbit by another, more distant orbiting body
- Lie algebra:
- Lie group:
- Lie transform: type of infinitesimal transform
- Lie transformation:
- life:
- light:
- light cone: region of space-time which you can see or can see you
- Light Curve:
- light cylinder:
- light echo: reflected light from an astronomical event arriving later
- light nebula:
- cloud: higher-density region of space
- reflection nebula: nebula made visible by light it scatters from nearby stars
- light neutrino:
- neutrino (ν): light, electrically neutral elementary particle
- light pollution: light from cities that interferes with astronomical observation
- Light satellite for the studies of B-mode polarization and inflation from cosmic background radiation detection:
- LiteBIRD: proposed spacecraft to map CMB polarization
- light speed:
- speed of light (c): fundamental constant measured as the speed at which light travels
- light's speed:
- speed of light (c): fundamental constant measured as the speed at which light travels
- light-year (ly): distance that light travels in a year
- parsec (pc): about 3.26 light-years
- lightcurve:
- lightkurve: software to analyze time series data
- LIGO: pair of observatories to detect gravitational waves
- LIGO A+:
- LIGO: pair of observatories to detect gravitational waves
- LIGO H:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Hanford Observatory:
- LIGO: pair of observatories to detect gravitational waves
- LIGO L:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Livingston Observatory:
- LIGO: pair of observatories to detect gravitational waves
- LIGO Voyager:
- LIGO: pair of observatories to detect gravitational waves
- LIGO-India: planned gravitational wave detector in India
- limb:
- limb darkening: the darkening of edge of a body such as the Sun
- limit:
- LINC/Nirvana:
- Lincoln Laboratory.:
- LINEAR: survey of near-Earth objects
- Lincoln Near-Earth Asteroid Research:
- LINEAR: survey of near-Earth objects
- Lindblad resonance:
- Lindblad torque: torque due to Lindblad resonances
- line:
- line blanketing: so many bunched spectral lines that they cannot be distinguished
- line broadening: processes causing a spectral line to have width
- line depth:
- line intensity mapping:
- line of beta stability:
- line of nodes:
- line profile:
- line series:
- line shape:
- line shape function: function describing the shape of a spectral line
- line-blanketing effect:
- line blanketing: so many bunched spectral lines that they cannot be distinguished
- LINEAR: survey of near-Earth objects
- linear algebra:
- linear GW memory:
- linear polarization:
- polarization: property of waves that oscillate in a particular direction
- linear system:
- linear theory: theory of operators satisfying the property of superposition
- linear theory: theory of operators satisfying the property of superposition
- linear variable filter:
- linearly variable filter (LVF): filter whose passband varies over one spatial dimension
- SPHEREx: all-sky spectral survey space-mission plan
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- LINER galaxy:
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- lines:
- lipid:
- Lego principle: principle that life is associated with a skew in molecule abundances
- liquid mirror:
- liquid mirror telescope: reflecting telescope with primary mirror formed of spinning liquid
- liquid planet: planet consisting of liquid
- liquid water habitable zone:
- liquid water zone:
- LIR:
- infrared (IR): electromagnetic radiation, wavelength .74-300 micrometers
- LIRG:
- LIRIS:
- LISA: proposed space mission to detect gravitational waves
- LISA Pathfinder:
- LISA: proposed space mission to detect gravitational waves
- LiteBIRD: proposed spacecraft to map CMB polarization
- lithium (Li): metal, Li, atomic number 3
- Littrow:
- LK oscillation:
- Kozai mechanism: an effect on an orbit by another, more distant orbiting body
- LkCl:
- Llano de Chajnantor Observatory:
- LLO:
- LIGO: pair of observatories to detect gravitational waves
- LMC:
- LMI:
- LMT:
- LMXB:
- Ln:
- lanthanide (Ln): element with atomic numbers 57 through 71
- lobe:
- local:
- Local Bubble:
- Local Group (LG): group of galaxies including the Milky Way
- local merger:
- Local Sheet: flat group of galaxies around the Local Group
- local standard of rest (LSR): velocity with respect to our region of the Milky Way
- Local Supercluster:
- local thermodynamic equilibrium (LTE): state where temperature variation is too small to matter
- Local Void: void next to the Local Group
- Local Volume (LV): region around the Local Group
- locally brightest galaxy:
- location:
- Lockman Cloud:
- Smith Cloud: high-velocity cloud on collision course with Milky Way
- Lockman Hole:
- LOFAR:
- LOFAR Prototype Station:
- LOPES: cosmic ray detector that detected resulting radio
- LOFAR Two-metre Sky Survey:
- LOFAR-core:
- logarithmic:
- LOLA:
- LONEOS: survey of near-Earth objects
- long gamma ray burst:
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- long period comet:
- Oort Cloud: cloud of comets and minor planets around the solar system
- long Rossby wave:
- Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
- long-period comet: comet with an orbital period of more than 200 years
- longitude of ascending node:
- lookback time:
- LOPES: cosmic ray detector that detected resulting radio
- Lorentz drag:
- Lorentz factor:
- Lorentz force: force on a point charge due to magnetic fields
- Lorentz invariance:
- Lorentz transform:
- Lorentz transformation: equations describing the effect of relative motion on length and velocity
- Lorenz transform:
- relativity: physics models accommodating the constancy of the speed of light
- LORRI:
- LOSS:
- LOTOSS:
- LoTSS:
- LOV:
- Love number: measures of rigidity of a body
- Love-Shida number:
- Lovell Telescope:
- Lovell Transit Telescope:
- Low Frequency Aperture Array:
- low frequency radio astronomy: astronomy using the lower end of the radio spectrum
- low mass star: stars of less than half the solar mass
- low resolution spectrograph.:
- HRS: high resolution spectrography
- low resolution spectrography:
- HRS: high resolution spectrography
- Low-frequency Array (LOFAR): low frequency radio telescope
- low-ionization nuclear emission-line region:
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- low-mass stars:
- low-mass X-ray binary:
- low-surface-brightness galaxy (LSB galaxy): galaxies less bright than those historically identified
- Lowell Observatory:
- Lowell Observatory Near-Earth-object Search:
- LONEOS: survey of near-Earth objects
- Lowell Proper Motion Survey (G): 1950s-1970s catalogs of stars with proper motion
- lowmass star:
- LP:
- LQG:
- LRG:
- LRIS:
- LRO:
- LROC:
- LRS:
- LRS2:
- LS:
- LSB galaxy:
- LSC:
- LSG:
- LSR:
- LSR velocity:
- LSS:
- LSST:
- Lsun:
- Sun: star at center of solar system
- LTE:
- LTG:
- galaxy: gravitationally-bound group of stars
- LTT:
- LUCI:
- lucky exposures:
- lucky imaging: method of combining short-term images to yield better resolution
- lucky imaging: method of combining short-term images to yield better resolution
- Luhman 16: nearby binary brown dwarf
- Luhman 16AB:
- luminosity (L): measure of brightness
- luminosity class: classification of size/luminosity of stars
- luminosity density: luminosity per unit volume
- luminosity distance (dL, DL): distance to an object based upon the distance's effect on received flux
- luminosity equation:
- luminosity function (LF): function giving number of stars or galaxies at different luminosities
- luminous infrared galaxy (LIRG): a galaxy emitting a lot of far-infrared light
- luminous red galaxy (LRG): distant bright red galaxies in the Sloan Digital Sky Survey
- luminous supergiant:
- lunar cold trap:
- moon: a planet's natural satellite, such as Earth's
- Lunar Crater Observation and Sensing Satellite:
- LCROSS: space probe observing the lunar poles
- Lunar Reconnaissance Orbiter (LRO): space probe orbiting the Moon
- Lunar Surface Gravimeter:
- lunar swirl: swirly spot on the surface of the Moon
- lunar water: water on the moon
- Lupus:
- Lupus Transit Survey: survey for hot Jupiters in a region of constellation Lupus
- LUVOIR: plan for a space-based 10 meter telescope
- Luyten 726-8: nearby binary star system
- Luyten Five Tenths Catalog:
- Luyten Half-second Catalog (LHS): 1979 catalog of 4000 stars with high proper motion
- Luyten Palomar Survey (LP): 1960s catalog of stars with high proper motion
- Luyten Two-Tenths Arcsecond Catalog (LTT): 1960 catalog of 9000+ stars with proper motion
- LV:
- LVF:
- LWCam:
- CCAT: 25 meter submillimeter telescope plan for Chile
- LWP:
- LWR:
- LWS:
- ly:
- light-year (ly): distance that light travels in a year
- Lyα:
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Ly-α:
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyapunov exponent:
- Lyapunov time: timescale over which a dynamical system is chaotic
- Lyapunov time: timescale over which a dynamical system is chaotic
- LyC photons:
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman:
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman-alpha emitter (LAE): redshifted galaxy emitting the Lyman alpha line
- Lyman-alpha forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- Lyman band:
- Lyman continuum escape:
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman continuum photons:
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman limit:
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman-break galaxy (LBG): a galaxy emitting very little shorter than 912 angstroms
- Lyman lines:
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman series: hydrogen series from electrons settling from n > 1 to n = 1
- Lyman-alpha emitter (LAE): redshifted galaxy emitting the Lyman alpha line
- Lyman-alpha emitting galaxy:
- Lyman-alpha forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
- Lyman-break galaxy (LBG): a galaxy emitting very little shorter than 912 angstroms
- Lyman-Werner photon: ultraviolet photon with proper energy to excite molecular hydrogen
- Lynds 1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Lynds Bright Nebula Catalog (LBN): 1950s/1960s list of bright nebulae found on Palomar plates
- Lynds Catalog of Dark Nebulae (LDN,L): 1950s/1960s list of dark nebulae found on Palomar plates
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- Lynx: concept for space X-ray observatory
- Lynx X-ray Observatory:
- Lynx: concept for space X-ray observatory
- Lynx-Ursa Major Filament:
- Lyon Observatory:
- Lyon-Meudon Extragalactic Database:
- Lyot stop: optical element to block unwanted light within instruments
- LZT:
index