Solar System

Butterfly diagram

The butterfly diagram is a time–latitude plot of sunspots, first drawn by Edward Maunder in 1904, showing spots migrate from mid-latitudes toward the equator over each solar cycle.

C Ring

The C Ring is the innermost of Saturn's main rings, discovered in 1850, lying between the D and B Rings and known for bright plateaus found nowhere else.

A C-type asteroid, also called a carbonaceous asteroid, is a dark, carbon-rich asteroid whose spectrum resembles carbonaceous chondrite meteorites; C-types form the largest asteroid class, dominating the outer main belt.

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/2023 A3 (紫金山) (Tsuchinshan–ATLAS)

Comet Tsuchinshan-ATLAS (C/2023 A3, 紫金山) is a long-period Oort cloud comet discovered in 2023 by China's Purple Mountain Observatory and the ATLAS survey, visible to the naked eye in October 2024.

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.

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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.

Carrington Event

The Carrington Event was the most intense geomagnetic storm in recorded history, striking Earth on September 1–2, 1859 after a solar flare observed by Richard Carrington.

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.

Catalina Sky Survey

The Catalina Sky Survey is a NASA-funded survey run by the University of Arizona that has discovered more near-Earth asteroids and comets than any other survey.

Cataloged lunar eclipses of antiquity and the Middle Ages

The cataloged lunar eclipses of antiquity and the Middle Ages are pre-1600 records of the Moon entering Earth's shadow, kept by Babylonian, Chinese, East Asian, and Islamic observers.

Centaur (small Solar System body)

A centaur, or centaur object, is a small icy body orbiting between Jupiter and Neptune and crossing at least one giant planet; the first found was Chiron, in 1977.

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.

Central lunar eclipses

A central lunar eclipse is one in which part of the Moon passes directly through the center of Earth's umbral shadow, always total and the longest type.

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.

Chang'e (嫦娥)

Chang'e (嫦娥), also known as Heng'e, is the Chinese goddess of the moon who floated there after drinking an elixir of immortality, and the namesake of China's lunar exploration program.

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.

Chirikov resonance overlap criterion

The Chirikov resonance overlap criterion, introduced by Boris Chirikov in 1959 to explain plasma confinement, is a heuristic rule stating that motion becomes chaotic when two nonlinear resonances overlap.

Chord (astronomy)

In astronomy, a chord is the straight-line segment a stellar occultation traces across a solar system body; chords from multiple sites fix the body's size, shape, and position.

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.

Chrysalis hypothesis

The Chrysalis hypothesis, proposed by Jack Wisdom of MIT and colleagues in Science in 2022, says Saturn lost a moon that once tilted its axis and became its rings.

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.

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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.

Classical planet

The classical planets, also called the traditional planets, are the seven moving celestial bodies of ancient astronomy: the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn.

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.