300 articles
C/2014 UN271 (Bernardinelli–Bernstein)
C/2014 UN271 (Bernardinelli–Bernstein), often shortened to Comet Bernardinelli–Bernstein, is a large Oort-cloud comet with a 137 km nucleus, found in Dark Energy Survey images and announced in June 2021.
C/2019 Y4 (ATLAS)
C/2019 Y4 (ATLAS) was a long-period comet discovered in December 2019 by the ATLAS survey in Hawaii, which brightened rapidly before disintegrating in April 2020.
C/2024 G3 (ATLAS)
C/2024 G3 (ATLAS) is a long-period comet discovered by the ATLAS survey in Chile in April 2024, which passed about 8 million miles from the Sun in January 2025.
Callisto (moon)
Callisto, also known as Jupiter IV, is the outermost of Jupiter's Galilean moons and the third largest moon in the solar system, roughly half ice and half rock.
Carpo
Carpo (Jupiter XLVI, S/2003 J 20) is a small prograde irregular moon of Jupiter about 3 km across, discovered in 2003, orbiting 17 million km out.
Cassini Division
The Cassini Division is the largest gap in Saturn's rings, a roughly 4,550 km-wide, low-density region between the B and A rings, first seen by Giovanni Cassini in 1675.
Center for Near-Earth Object Studies
The Center for Near-Earth Object Studies (CNEOS) is a NASA office at the Jet Propulsion Laboratory in Pasadena, California, computing precise orbits for near-Earth asteroids and comets.
Ceres (dwarf planet)
Ceres is the largest object in the asteroid belt and the only dwarf planet in the inner solar system, discovered by Giuseppe Piazzi in 1801.
Charon (moon)
Charon, also known as Pluto I, is the largest moon of Pluto and the largest known satellite relative to its parent, discovered in 1978 and imaged by New Horizons in 2015.
Chromosphere
The chromosphere is the roughly 2,500 km thick layer of the Sun's atmosphere above the photosphere, glowing red from hydrogen-alpha emission and visible during total eclipses.
Circumbinary planet
A circumbinary planet is a planet that orbits both stars of a binary star system rather than one star. The first confirmed example was Kepler-16b, discovered by NASA's Kepler mission in 2011.
Citlalpul Vallis
Citlalpul Vallis is an IAU-named (1994) canali-type channel system on Venus, centered at 51.8S, 187E with a 3,160 km diameter; its Aztec name means the planet Venus, and it forms the eastern extent of a 3,000-km-long canali system with Xulab Vallis.
Clearing the neighbourhood
Clearing the neighborhood, also called dynamical dominance, is the third criterion in the IAU's 2006 planet definition, distinguishing the eight planets from dwarf planets such as Pluto.
Climate of Mars
The climate of Mars, also called the Martian climate, is the weather pattern of the planet's thin carbon dioxide atmosphere, with cold temperatures, seasons, and planet-encircling dust storms.
Climate of Uranus
The climate of Uranus covers temperatures, winds, and seasons on the ice giant tilted 98° on its side, where each season lasts about 21 years and winds reach 900 km/h.
CNEOS 2014-01-08
CNEOS 2014-01-08, also called IM1, is a fireball detected off Papua New Guinea in 2014, identified by Harvard's Siraj and Loeb as a likely interstellar meteor.
Comet
A comet is a small solar system body of ice, rock, and dust that orbits the Sun and grows a coma and often one or more tails.
Comet Lovejoy
C/2011 W3 (Lovejoy) is a Kreutz sungrazing comet discovered by Australian amateur astronomer Terry Lovejoy in November 2011, which became the first sungrazer known to survive its perihelion passage.
Comet nucleus
A comet nucleus is the solid, icy central body of a comet, typically a few miles across, which sublimates near the Sun to feed the coma and tails.
Comet tail
A comet tail, also called a cometary tail, is a stream of gas and dust pushed away from a comet by the Sun's radiation and solar wind.
Contact binary (small Solar System body)
A contact binary is a small Solar System body made of two formerly separate lobes joined at a narrow neck, like the asteroids Itokawa and Arrokoth.
Convection zone
The convection zone is the Sun's outermost interior layer, where convection rather than radiation carries energy to the visible surface, spanning the outer third by radius.
Cordelia (moon)
Cordelia, also designated Uranus VI, is the innermost known moon of Uranus, a roughly 20 km satellite discovered by Voyager 2 in 1986 that shepherds the epsilon ring.
Core accretion model
The core accretion model is the leading theory of giant planet formation, in which a solid core of rock and ice grows until it triggers runaway gas accretion.
Core of Mars
The core of Mars is the planet's central region of liquid iron and nickel alloy, made unusually light-element-rich, and measured seismically by NASA's InSight lander between 2018 and 2022.
Coronal heating problem
The coronal heating problem is the unsolved question of why the Sun's outer atmosphere, the corona, reaches 1–2 million kelvin while the surface below is only about 6000 K.
Coronal hole
A coronal hole is a dark, cooler, less dense region of the Sun's corona with open magnetic field lines, the source of the fast solar wind.
Coronal loop
A coronal loop is an arch-shaped structure of hot plasma in the Sun's corona following closed magnetic field lines, best seen in X-ray and ultraviolet telescopes.
Coronal mass ejection
A coronal mass ejection (CME), also called a coronal transient, is a large eruption of magnetized plasma from the Sun's corona that drives the strongest geomagnetic storms at Earth.
Coronal rain
Coronal rain is cool, dense plasma condensing in the Sun's corona that falls along magnetic loops, formed by thermal instability and used to probe coronal heating.