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List of largest cosmic structures
The list of largest cosmic structures covers galaxy walls, large quasar groups, and superstructures spanning hundreds of megaparsecs, from the Sloan Great Wall to Quipu.
List of nearest exoplanets
The list of nearest exoplanets covers the confirmed planets orbiting stars within about 20 light-years of the Sun, a set dominated by small planets around red dwarfs, the closest being Proxima Centauri b.
List of space telescopes
The list of space telescopes, also called list of space observatories, covers orbiting observatories from 1970s Uhuru to Webb, spanning X-ray, visible, and infrared wavelengths.
Lists of astronomical objects
Lists of astronomical objects, also known as lists of celestial bodies, are catalogs recording stars, galaxies, and exoplanets, ranging from ancient star lists to modern surveys like Gaia.
LiteBIRD
LiteBIRD is a JAXA space mission that will map the polarization of the cosmic microwave background over the entire sky to test cosmic inflation, targeting launch in 2036.
Local Volume
The Local Volume is the region of space around the Milky Way containing about 1000 known galaxies within 11 megaparsecs, organized into seven mostly dwarf groups and used to test cosmology.
LOFAR
LOFAR (LOw Frequency ARray) is a European radio telescope operating at 10 to 240 MHz, the largest of its kind at the lowest observable frequencies.
Long Wavelength Array
The Long Wavelength Array (LWA) is a radio telescope in New Mexico and California observing at 10 to 88 MHz, the lowest frequencies observable from the ground.
Long-baseline interferometry
Long-baseline interferometry is an observational astronomy technique that combines signals from telescopes separated by long distances, resolving fine detail in celestial sources at radio, optical, and infrared wavelengths.
Long-slit spectroscopy
Long-slit spectroscopy is an astronomical observing technique that disperses light from a narrow strip of sky, recording a separate spectrum for each point along the slit.
Loop quantum cosmology
Loop quantum cosmology (LQC) applies loop quantum gravity to the early universe, replacing the big bang singularity with a quantum bounce; its predicted effects may leave imprints in the cosmic microwave background.
Lovell Telescope
The Lovell Telescope is a 76-meter fully steerable radio telescope at Jodrell Bank Observatory in Cheshire, England, completed in 1957 and named for Bernard Lovell, who conceived it.
Low-luminosity AGN
A low-luminosity active galactic nucleus (LLAGN) is a weak active galactic nucleus whose X-ray output falls below 10^42 erg/s, the most numerous AGN in the local Universe.
Lowell Observatory
Lowell Observatory is a private nonprofit observatory founded by Percival Lowell in 1894 on Mars Hill in Flagstaff, Arizona, best known for the 1930 discovery of Pluto.
LST-1
LST-1 (Large-Sized Telescope 1) is the first of the Large-Sized Telescopes of the Cherenkov Telescope Array Observatory, inaugurated in 2018 on La Palma, Spain, and taking science data since 2019.
Luminosity distance
Luminosity distance is the distance assigned to an astronomical object by comparing its observed flux with its intrinsic luminosity; Type Ia supernovae and gravitational-wave standard sirens measure it to probe cosmic expansion.
Lyman-alpha emitter
A Lyman-alpha emitter is a galaxy selected by strong hydrogen Lyman-alpha emission, typically a young, compact, metal-poor star-forming galaxy used to probe reionization and the early universe.
Lyman-alpha forest
The Lyman-alpha forest is the dense set of absorption lines from neutral hydrogen in the spectra of distant quasars, tracing the intergalactic medium along the line of sight.
M51-ULS-1
M51-ULS-1 is an ultraluminous supersoft X-ray source in the Whirlpool Galaxy, 28 million light-years away, host of M51-ULS-1b, the first candidate planet beyond the Milky Way.
M82
M82, also called the Cigar Galaxy, is a starburst galaxy in Ursa Major about 12 million light-years from Earth, forming stars ten times faster than the Milky Way.
Macquart relation
The Macquart relation is the observed link between a fast radio burst's dispersion measure and its host galaxy's redshift, established in a 2020 Nature study led by J.-P. Macquart.
Magellan Telescopes
The Magellan Telescopes, named Baade and Clay, are twin 6.5-meter optical telescopes at Las Campanas Observatory in Chile's Atacama Desert, with Baade seeing first light in 2000.
MAGIC stereo system
The MAGIC stereo system, also called the MAGIC Florian Goebel Telescopes, is a pair of 17-meter gamma-ray Cherenkov telescopes on La Palma, Spain, operating together since 2009.
Magnitude (astronomy)
Magnitude, also called star magnitude, is astronomy's logarithmic measure of celestial brightness: five magnitudes equal a 100-fold brightness difference, so brighter objects carry smaller or negative numbers.
Markarian 421
Markarian 421, or Mrk 421, is a nearby blazar, a giant elliptical galaxy with a jet aimed at Earth, first detected at TeV gamma rays in 1992 by the Whipple Observatory.
Markarian 501
Markarian 501, also known as Mrk 501, is a nearby blazar, a type of galaxy with a jet pointed at Earth, and a source of TeV gamma rays.
Mass-to-light ratio
The mass-to-light ratio (M/L) is the mass of a galaxy or galaxy cluster divided by its light, a diagnostic of unseen dark matter first applied by Fritz Zwicky in 1933.
Matter-dominated era
The matter-dominated era is the period of cosmic history, beginning about 50,000 years after the Big Bang, when matter's density exceeded radiation's and drove cosmic expansion.
Matter–radiation equality
Matter–radiation equality is the epoch in the early universe, about 51,000 years after the Big Bang at redshift roughly 3400, when matter first outweighed radiation, allowing density fluctuations to grow.
McDonald Observatory
McDonald Observatory is an astronomical observatory in West Texas's Davis Mountains, operated by The University of Texas at Austin and home to the Hobby-Eberly Telescope, one of the world's largest.