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James Clerk Maxwell Telescope
The James Clerk Maxwell Telescope (JCMT) is a 15-meter radio telescope near the summit of Maunakea, Hawaii, and the world's largest telescope built for submillimetre astronomy.
Jantar Mantar (जंतर मंतर)
Jantar Mantar (जंतर मंतर), also called Yantra Mandir, is an astronomical observatory in Jaipur, India, built by Sawai Jai Singh II and completed in 1738, with about twenty large masonry instruments used for naked-eye observation.
Jantar Mantar, New Delhi
Jantar Mantar in New Delhi is an 18th-century open-air astronomical observatory built in 1724 by Maharaja Sawai Jai Singh II of Jaipur, the first of his five such observatories.
Jessica Meir
Jessica Meir, also known as Jessica Ulrika Meir, is an American NASA astronaut and marine physiologist who performed the first all-female spacewalk in 2019 and commanded SpaceX Crew-12 in 2026.
John Herschel
John Herschel (1792–1871) was an English astronomer, chemist, and philosopher of science, son of William Herschel, who completed his father's survey of the skies from Cape Town and helped found photography.
JWST exoplanet atmosphere spectroscopy
JWST exoplanet atmosphere spectroscopy measures how starlight filtered through an exoplanet's atmosphere changes with infrared wavelength, revealing composition, temperature, and clouds on planets outside the Solar System.
JWST infrared spectroscopy
JWST infrared spectroscopy is the observation of infrared spectra by the James Webb Space Telescope, whose four instruments cover 0.6 to 28 micrometers from Lagrange point 2.
K-essence
K-essence is a class of dark energy models where a scalar field with non-canonical kinetic terms, not just its potential, drives the universe's late-time accelerated expansion.
K2-18b
K2-18b is a temperate sub-Neptune exoplanet orbiting the red dwarf K2-18 in Leo, about 120 light-years away, discovered in 2015 and known for contested signs of life.
Kali ahargana
Kali ahargana is the count of civil days since the Kali Yuga epoch of 18 February 3102 BCE, used in Indian astronomy to compute planetary positions.
Kavli Institute for Cosmological Physics
The Kavli Institute for Cosmological Physics (KICP) is a University of Chicago research institute studying dark energy, dark matter, and inflation; founded in 2001, it was renamed in 2004 after a Kavli Foundation endowment.
KBC void
The KBC void, also called the Local Hole, is a proposed region around the Local Group about 20 percent less dense than the cosmic average, extending roughly 300 megaparsecs.
Kepler-186f
Kepler-186f is an Earth-size exoplanet about 500 light-years away in the constellation Cygnus, announced in 2014 as the first Earth-size planet found orbiting a red dwarf within its habitable zone.
Kepler-442b
Kepler-442b, also designated KOI-4742.01, is a super-Earth exoplanet orbiting the K-type star Kepler-442 in Lyra, about 1,200 light-years away, announced in 2015 and ranked among the most Earth-like planets known.
Kepler-452b
Kepler-452b is a candidate super-Earth exoplanet orbiting the Sun-like star Kepler-452 about 1,400 light-years away, announced in 2015 as a possibly rocky planet in the habitable zone, though a 2018 reanalysis left it unconfirmed.
KiDS+VIKING
KiDS+VIKING is the combination of two ESO imaging surveys, the optical Kilo-Degree Survey and the near-infrared VIKING survey, used for weak lensing cosmology; its KiDS-1000 analysis found a 3σ tension with Planck.
KOI-5715.01
KOI-5715.01 is an unconfirmed transiting planet candidate in NASA's Kepler KOI catalog, about 1.93 Earth radii wide, orbiting the K-type star KOI-5715 every 190 days at 0.6066 astronomical units.
La Silla Observatory
La Silla Observatory is an astronomical observatory operated by the European Southern Observatory on La Silla mountain in Chile's Atacama Desert, ESO's first, inaugurated in 1969.
Lambda-CDM model (ΛCDM)
Lambda-CDM, or ΛCDM, is the standard six-parameter model of cosmology, describing a flat 13.8-billion-year-old universe of cold dark matter and dark energy, though it faces tensions in measurements of the Hubble constant.
Large Binocular Telescope
The Large Binocular Telescope (LBT) is an optical and infrared observatory on Mount Graham, Arizona, whose two 8.4 m mirrors give it the collecting area of an 11.8 m telescope.
Large Millimeter Telescope
The Large Millimeter Telescope (LMT), known in Mexico as the Gran Telescopio Milimétrico Alfonso Serrano, is a 50-meter radio telescope at 4600 m on Sierra Negra, Puebla, Mexico.
Large quasar group
A large quasar group is a grouping of quasars closely matched in redshift and position, implying a larger dimmer structure; the Huge-LQG was the largest known structure in 2013.
Large Sky Area Multi-Object Fiber Spectroscopic Telescope
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), also called the Guoshoujing Telescope, is a Chinese telescope that takes spectra of 4,000 objects at once.
Large-scale structure of the universe
The large-scale structure of the universe, known as the cosmic web, is the pattern in which galaxies cluster along filaments and sheets surrounding vast voids.
Legacy Survey of Space and Time
The Legacy Survey of Space and Time (LSST) is a ten-year optical survey of the southern sky by the Vera C. Rubin Observatory in Chile, begun in 2026.
Lick Observatory
Lick Observatory is a University of California astronomical observatory on Mount Hamilton near San Jose, founded in 1888 and the world's first permanently staffed mountain-top observatory.
Light curve analysis
Light curve analysis is the set of techniques for measuring and modeling a celestial object's brightness over time, revealing periods, masses, and shapes of variable stars, planets, and asteroids.
Light dark matter
Light dark matter is dark matter with particle masses below about 1 GeV, far lighter than WIMPs, so conventional nuclear-recoil detectors cannot see it; electron-scattering experiments like DarkSide-50 search for it.
Line intensity mapping
Line intensity mapping (LIM) is an observational technique that maps integrated spectral-line emission from unresolved galaxies and the diffuse intergalactic medium, tracing large-scale structure across nearly the universe's entire history.
List of exoplanets discovered in 2026
A list of the exoplanets discovered in 2026 as recorded by the NASA Exoplanet Archive, including Beta Pictoris d, Gaia23braL b, and the habitable-zone Gl 725 B c.