Term Index (L)
- L:
- L band:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- L dwarf:
- brown dwarf (BD): star-like object with less mass than a star
- L-type star (L): spectral type of star cooler than an M-type star
- Lépine Shara Proper Motion catalog (LSPM): 2000s catalog of stars with proper motion
- L'institute Canadian d'astrophysique théorique:
- L-class:
- L-type star (L): spectral type of star cooler than an M-type star
- l-m plane:
- u-v plane: plane for displaying Fourier transforms of signal from the sky
- L-point:
- L-type star (L): spectral type of star cooler than an M-type star
- L1:
- L1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- L2:
- L3:
- L4:
- 2010 TK7: asteroid that is an Earth Trojan
- Lagrangian point: points around two orbiting bodies where small objects can sit
- L5:
- Lagrange: future pair of space-weather warning satellites
- Lagrangian point: points around two orbiting bodies where small objects can sit
- L500:
- LBol:
- LIR:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- LSun:
- La Palma:
- La Palma Observatory:
- La Silla Observatory (LSO): Atacama-desert observatory run by ESO
- La Silla Paranal Observatory (LPO): manages three ESO observatory sites in Chile
- LABOCA:
- LABOCA ECDFS Submillimeter Survey:
- LABOCA ECDFS Submm Survey:
- LABOCA Extended Chandra 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 twelfth nearest star system
- Lacaille Star Catalog (Lac): 1700s catalog of about 10,000 southern hemisphere stars
- LAE:
- Laevens:
- Laevens 2:
- Lagrange: future pair of space-weather warning satellites
- Lagrange point:
- Lagrange point stability:
- Lagrange stability: a quality of some stable orbits
- Lagrangian code:
- Lagrangian libration point:
- Lagrangian point: points around two orbiting bodies where small objects can sit
- LAL:
- Lalande:
- Lalande 21185: nearby red dwarf
- Lalande 21185 b:
- LAM:
- LAMBDA: NASA archive center re CMB data
- Lambda Boötis star (λ Boo): peculiar star with metallicity only with lighter elements
- Lambda CDM model:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- laminar flow:
- Rayleigh number (Ra): measure reflecting a fluid system's propensity to turbulence
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
- turbulence: irregular flow of a fluid
- 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:
- Landsat 7:
- OSAM-1: prototype space robot for servicing satellites
- Lane-Emden equation: form of equation of state for gas ball in hydrostatic equilibrium
- Langmuir probe (LP): plasma sensor
- Laniakea:
- Laniakea Supercluster: group of clusters including the Local Group
- lanthanide (Ln): element with atomic numbers 57 through 71
- kilonova (KN): explosive event larger than a nova and smaller than a supernova
- 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
- Laplacian:
- Large Altazimuth Telescope (BTA-6): 6-meter reflector telescope in Russia
- Large Aperture Telescope:
- 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): somewhat 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: gravitational wave detector in Japan preparing for operation
- 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:
- Rubin Observatory (VRO,LSST): 8-meter survey reflector telescope under construction in Chile
- Large UV/Optical/Infrared Surveyor:
- LUVOIR: plan for a space-based telescope
- Large Zenith Telescope (LZT): 6 meter liquid mirror telescope in British Columbia
- Large-Scale Polarization Explorer:
- LSPE-STRIP: CMB survey telescope in Canary Islands
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- Large-Scale Polarization Explorer/Short Wavelength Instrument for the Polarization Explorer:
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- Large-Scale Polarization Explorer/Survey Tenerife Polarimeter:
- LSPE-STRIP: CMB survey telescope in Canary Islands
- LAS:
- UKIDSS: five-part infrared survey using UKIRT
- Las Campanas Observatory (LCO): observatory in southern Atacama Desert
- Las Campanas Redshift Survey (LCRS): 1990s survey of galaxies out to z = 0.2
- Las Cumbres Observatory (LCO): world-wide network of telescopes
- Las Cumbres Observatory Global Telescope:
- LASCO:
- LASCO C1:
- LASCO C2:
- LASCO C3:
- 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
- maser: electromagnetic radiation amplified by stimulated emission
- laser guide star:
- adaptive optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- guide star (GS): star used to assist in astronomical observation
- Laser Interferometer Gravitational-wave Observatory:
- LIGO: pair of observatories to detect gravitational waves
- Laser Interferometer Space Antenna:
- laser tomography AO:
- adaptive optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- LaSilla QUEST Survey:
- LaSilla-QUEST Variability Survey (LSQ): survey for transients
- LASS:
- HEAO-1: 1977 X-ray observatory space mission
- last parsec problem:
- last scattering surface:
- LAT:
- LAT All-sky Survey:
- Fermi (FGST,GLAST): satellite for studying gamma rays
- late:
- spectral class: overall classification of stars based upon spectral features
- spectral type: classification of stars based upon spectral features
- late heavy bombardment (LHB): time after solar system planet-formation when many impacts occurred
- late thermal pulse:
- thermal pulse: pulse in an AGB star due to helium fusion in a shell
- late time anisotropies:
- late-type galaxy:
- galaxy: gravitationally-bound group of stars
- late-type nitrogen-rich Wolf-Rayet:
- late-type star:
- spectral class: overall classification of stars based upon spectral features
- spectral type: classification of stars based upon spectral features
- latent heat:
- latitude:
- circle of latitude: circle around the Earth of points equidistant from a pole or the equator
- lattice Boltzmann method (LBM): computational fluid dynamics method treating the fluid as particles
- Latysev:
- LAU:
- launch window: time period for launching space probes traveling a particular route
- law of cosmic censorship: a singularity cannot be observed
- law of gravitation:
- law of refraction:
- LAWD:
- Lawrence Lowell Telescope:
- laws of black hole mechanics:
- laws of thermodynamics:
- LB:
- LB-1: binary star with evidence of a black hole
- LBA:
- LBC:
- LBG:
- LBM:
- LBN:
- LBQS:
- LBS:
- MMX: Japanese probe to bring back a sample of a Martian moon
- LBT:
- LBTI:
- LBTI/LMIRCAM:
- LBTI/NOMIC:
- LBV:
- LBV outburst:
- LC:
- LCDM:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- LCGT:
- KAGRA: gravitational wave detector in Japan preparing for operation
- LCL:
- LCO:
- LCOGT:
- LCROSS: space probe observing the lunar poles
- LCRS:
- LCT:
- LDN:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- LDS:
- LDSS3:
- LDT:
- Le Gentil:
- lead star:
- leakage neutron:
- leap day:
- leap year:
- sidereal: relative to the fixed position of the stars
- learning:
- LECP:
- Voyager: space probes to observe planets and the edge of the solar system
- LECS:
- BeppoSAX: Italian-Dutch space X-ray telescope
- 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
- legacy survey: phrase sometimes used in survey names
- 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
- LEHPM:
- Leiden Observatory:
- Leighton Chajnantor Telescope:
- LEKID:
- KID: type of sensitive electronic device to detect light
- Lempo:
- LENA:
- IMAGE: satellite mission to study magnetosphere
- LEND:
- length contraction:
- lensing deflection field:
- lensing map:
- lenslet array:
- lensmaker's equation:
- lensmaker's formula:
- lenticular galaxy (S0): disk galaxy that has no spirals
- LEO:
- Leo Cluster:
- Leo I:
- Leo II:
- Leo IV:
- Leo T:
- Leo V:
- lepton:
- baryon: protons, neutrons, and other three-quark particles
- particle: very small thing
- LESS:
- LETG:
- 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
- LGA:
- beam: portion of a sky that a radio telescope is viewing
- LGG:
- LGM-1:
- pulsar (PSR): type of astronomical body with EMR in regular cycles of seconds or less
- LGRB:
- LGRS:
- GRAIL: 2011 NASA lunar orbiters to collect gravity data
- LGS:
- LH:
- LHA:
- LHB:
- LHCP:
- polarization: property of waves that oscillate in a particular direction
- LHO:
- LIGO: pair of observatories to detect gravitational waves
- rare designator prefixes: designator prefixes generally used for only a few objects
- 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
- LHS 3844:
- LHS 3844 b: red dwarf with rocky planet in its habitable zone
- LHS 3844 b: 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 can sit
- libration: oscillating motion of orbiting bodies relative to each other
- LIC:
- Lick indices: defined set of spectral line indexes for stars
- Lick Observatory: California observatory of long standing
- 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
- LID:
- LAMOST: Chinese telescope for spectroscopic surveys of stars and galaxies
- 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 amplification by stimulated emission of radiation:
- maser: electromagnetic radiation amplified by stimulated emission
- 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: planned 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: the edge of an astronomical object as viewed
- limb darkening: the darkening of edge of a body such as the Sun
- limb: the edge of an astronomical object as viewed
- transiting planet: planet crossing between another body and the observer
- Limber approximation: formula approximating the density of galaxies in some direction
- Limber equation:
- Limber formula:
- limit:
- limiting magnitude: faintest magnitude that a telescope or instrument can detect
- 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
- CMFGEN: RT code designed to handle significant stellar wind
- line broadening: processes causing a spectral line to have width
- line broadening function:
- line depth:
- line index:
- 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 tomography: using double-peaked spectral lines to place constituents of a disk
- 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:
- lipids:
- Lego principle: principle that life is associated with a skew in molecule abundances
- liquid mirror:
- liquid mirror telescope: reflector 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 0.74-300 micrometers
- LIRG:
- LIRIS:
- LISA: proposed space mission to detect gravitational waves
- LISA Pathfinder:
- LISA: proposed space mission to detect gravitational waves
- Lissajous orbit:
- halo orbit: type of orbit around an instable Lagrangian point
- LiteBIRD: planned spacecraft to map CMB polarization
- lithium (Li): metal, Li, atomic number 3
- lithium burning: any fusion reaction starting with lithium
- lithosphere:
- lithospheric flexure:
- elastic thickness (Te): measure of the thickness of a sagging layer of a planet surface
- Littrow:
- Livermore Optical Transient Imaging System (LOTIS): automated telescope aiming to catch GRB optical counterparts
- Liverpool Telescope:
- LK oscillation:
- Kozai mechanism: an effect on an orbit by another, more distant orbiting body
- LkCl:
- LLAGN:
- Llano de Chajnantor Observatory: group of observatories on a high plateau of the Atacama Desert
- LLO:
- LIGO: pair of observatories to detect gravitational waves
- lm plane:
- u-v plane: plane for displaying Fourier transforms of signal from the sky
- LMC:
- LMC AB:
- LMI:
- LMPO:
- protostar: contracted mass of gas that will become a star
- LMS:
- LMT:
- LMXB:
- Ln:
- lanthanide (Ln): element with atomic numbers 57 through 71
- Lo:
- load density: measure of rigidity of the crust of a body
- LOAN:
- lobe:
- local:
- Local Arm:
- spiral arm: long, winding visible structure within a spiral galaxy
- Local Bubble: ISM shell in which the solar system resides
- Local Cavity:
- local flow:
- Local Fluff:
- Local Group (LG): group of galaxies including the Milky Way
- Local Interstellar Cloud (LIC): local ISM region with slightly higher density of hydrogen
- local merger:
- local meridian:
- meridian circle: instrument for timing the passage of stars over a meridian
- local oscillator:
- Local Sheet: flat grouping 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
- Local Volume Mapper:
- locally brightest galaxy:
- location:
- Lockman Cloud:
- Smith Cloud: high-velocity cloud on collision course with Milky Way
- Lockman hole: region of sky with little Milky-Way neutral hydrogen
- 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 Baseline Array (LBA): radio interferometer using Australian telescopes
- long gamma ray burst:
- long period comet:
- Oort Cloud: cloud of comets and minor planets around the solar system
- long period variable:
- 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:
- Loop I Bubble:
- loose group:
- galaxy group: group of fifty or fewer gravitationally bound Milky-Way-sized galaxies
- 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
- spacetime: four dimensions: time and the three space dimensions
- Lorentzian distribution: probability distribution applicable to some physics phenomena
- damping profile: mathematical shape that models some types of spectral line broadening
- Lorentzian function:
- Lorentzian profile:
- damping profile: mathematical shape that models some types of spectral line broadening
- Lorenz transform:
- relativity: physics models accommodating the constancy of the speed of light
- Lorimer burst:
- fast radio burst (FRB,FRT): astronomical high energy radio pulses of a few milliseconds
- LORRI:
- Los Alamos National Laboratory:
- LOSS:
- loss cone:
- LOTIS:
- LOTOSS:
- LoTr:
- LoTSS:
- LOV:
- Love number: measures of rigidity of a body
- Love-Shida number:
- Lovell Telescope:
- Lovell Transit Telescope:
- Lovelock gravity: generalization of general relativity
- Lovelock theory of gravity:
- Low Frequency Aperture Array:
- low frequency radio astronomy: astronomy using the lower end of the radio spectrum
- low gain antenna:
- beam: portion of a sky that a radio telescope is viewing
- low mass star (LMS): stars of less than half the solar mass
- low resolution spectrograph.:
- HRS: high resolution spectrography
- low resolution spectrography:
- HRS: high resolution spectrography
- low surface gravity:
- 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 protostellar object:
- protostar: contracted mass of gas that will become a star
- low-mass stars:
- low-mass X-ray binary:
- low-surface-brightness galaxy (LSB galaxy): galaxies less bright than those historically identified
- Lowell Discovery Telescope (LDT,DCT): 4.3 m telescope at Lowell Observatory, Arizona
- Lowell Observatory: Arizona observatory of long standing
- 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
- lower meridian:
- lowmass star:
- LP:
- LPM:
- LPO:
- LPV:
- LQG:
- LRG:
- LRIS:
- LRN:
- LRO:
- LROC:
- LRS:
- Hobby-Eberly Telescope (HET,SST): 10 meter telescope in Texas
- HRS: high resolution spectrography
- IRAS: 1983 satellite that surveyed the sky in infrared
- LRS2:
- LS:
- LSB galaxy:
- LSC:
- LSE:
- LSG:
- LSO:
- LSPE:
- LSPE-STRIP: CMB survey telescope in Canary Islands
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- LSPE-STRIP: CMB survey telescope in Canary Islands
- LSPE-SWIPE: plan for a balloon-based CMB polarization survey
- LSPM:
- LSQ:
- LSR:
- LSR velocity:
- LSS:
- LSST:
- Lsun:
- Sun: star at center of solar system
- LT:
- LTE:
- LTG:
- galaxy: gravitationally-bound group of stars
- LTMO:
- adaptive optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- LTP:
- thermal pulse: pulse in an AGB star due to helium fusion in a shell
- 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:
- 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
- luminosity-decline rate relation:
- luminous blue variable (LBV): type of extremely bright variable stars
- 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 red nova (LRN): red-colored event theorized to be a merger of two stars
- luminous supergiant:
- lumped element KID:
- KID: type of sensitive electronic device to detect light
- 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 telescope
- LUVOIR-A:
- LUVOIR: plan for a space-based telescope
- LUVOIR-B:
- LUVOIR: plan for a space-based telescope
- LUX:
- ZEPLIN: experiment to identify WIMPs with a tank of xenon
- LUX-ZEPLIN:
- ZEPLIN: experiment to identify WIMPs with a tank of xenon
- LUY:
- Luyten 726-8: nearby binary star system
- Luyten Double Star Survey (LDS): 1940s-1970s catalog of double stars
- 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:
- LVM:
- LW flux:
- LW radiation:
- LWCam:
- CCAT: 25-meter submillimeter telescope plan for Chile
- LWP:
- LWR:
- LWS:
- Ly:
- Lyα:
- Ly-α:
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Ly-β:
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyapunov exponent:
- Lyapunov time: timescale over which a dynamical system is chaotic
- Lyapunov orbit:
- halo orbit: type of orbit around an instable Lagrangian point
- Lyapunov time: timescale over which a dynamical system is chaotic
- LyC photons:
- Lyman series (L,Ly): 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 (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyman alpha (Ly-α,Lyα): first line in the Lyman series
- Lyman series (L,Ly): 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 beta:
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyman continuum escape:
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyman continuum photons:
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyman limit:
- Lyman series (L,Ly): 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 (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- Lyman series (L,Ly): hydrogen series from electrons settling from n > 1 to n = 1
- hydrogen (H): most prominent element, atomic number 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-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 flux:
- Lyman-Werner photon: ultraviolet photon with proper energy to excite molecular hydrogen
- Lyman-Werner radiation:
- Lynds 1689:
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- 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
- Lynds Catalogue of Bright Nebulae (LBN): 1950s/1960s list of bright nebulae found on Palomar plates
- 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 coronagraph (CLC): original coronagraph design
- Lyot stop: optical element to block unwanted light within instruments
- LZ:
- ZEPLIN: experiment to identify WIMPs with a tank of xenon
- LZT:
Index