300 articles
Cressida
Cressida (Uranus IX, S/1986 U3) is a small inner moon of Uranus, 41 km in radius, discovered by Voyager 2 in January 1986 and named for Shakespeare's Troilus and Cressida; its 3:2 resonance with the eta ring allowed its mass to be measured.
Cryovolcanism on Ceres
Cryovolcanism on Ceres is the eruption of cold, salt-rich brines onto the dwarf planet Ceres, which NASA's Dawn orbiter found shaped features like Ahuna Mons and Occator crater.
Cyllene (moon)
Cyllene, also designated Jupiter XLVIII and provisionally S/2003 J 13, is a small retrograde irregular moon of Jupiter about 2 km across, discovered in 2003 by Scott S. Sheppard's team.
Daphnis (moon)
Daphnis is a small moon of Saturn, about 8 kilometers across, discovered by Cassini in 2005. It orbits inside the Keeler Gap, sculpting its edges into waves.
Daura Chasma
Daura Chasma is a 729-km-long chasma, or extensional rift trough, on Venus, centered at 73.8°N, 53.8°E. IAU-approved in 1985, it is named for a Hausa great huntress of western Sudan.
Definition of planet
The definition of planet, also called the IAU definition of planet, is the 2006 International Astronomical Union resolution requiring a body to orbit the Sun, be nearly round, and clear its orbital neighborhood.
Deimos (moon)
Deimos, also known as Mars II, is the smaller and outer moon of Mars, discovered by Asaph Hall in 1877 and named for the Greek personification of flight.
Despina (moon)
Despina (Neptune V, provisional designation S/1989 N 3) is a small inner moon of Neptune about 148 kilometers across, discovered by Voyager 2 in 1989 as it orbits within the planet's faint ring system.
Diamond rain
Diamond rain is the hypothesized precipitation of solid diamond crystals through the mantles of ice giants like Uranus and Neptune, an idea proposed by Marvin Ross in 1981 and tested in laboratory experiments since.
Differential rotation
Differential rotation is when different latitudes of a gaseous body rotate at different speeds, seen in the Sun, where the equator spins in 25 days and the poles in 36.
Dione (moon)
Dione is the fourth-largest moon of Saturn, an icy satellite about 1,123 km across that orbits every 2.7 days and is known for its bright wispy terrain.
Dwarf planet
A dwarf planet is a celestial body that orbits the Sun, is nearly round, and has not cleared its orbital neighborhood, a category created in 2006.
Dysnomia (moon)
Dysnomia is the only known moon of the dwarf planet Eris, discovered in 2005 and named for the Greek goddess of lawlessness, daughter of Eris.
E Ring
The E Ring is the outermost of Saturn's named rings, a faint, diffuse band of water-ice grains continuously supplied by the geysers of the moon Enceladus.
Earth
Earth is the third planet from the Sun and the largest of the four terrestrial planets, a 4.54-billion-year-old rocky world with one moon, large surface oceans, and the only known life.
Earth Similarity Index
The Earth Similarity Index (ESI) is a numerical scale from 0 to 1 comparing a planet's physical properties with Earth's, introduced in 2011 to screen exoplanets.
Effective temperature
Effective temperature is the temperature at which a blackbody would radiate the same total power as a source; Earth's is 254.0 K against a surface mean of 15°C.
Eirene (moon)
Eirene, officially Jupiter LVII and once designated S/2003 J 5, is a small retrograde irregular moon of Jupiter in the Carme group, discovered by Scott S. Sheppard in 2003.
Enceladus
Enceladus is an icy moon of Saturn, about 310 miles across, that vents water vapor and ice into space from a global ocean beneath its ice shell.
Epimetheus (moon)
Epimetheus is a small, cratered moon of Saturn, about 116 km across, that shares its orbit with Janus; the two swap places roughly every four years.
Equilibrium temperature
The equilibrium temperature of a planet is the temperature at which absorbed stellar power equals emitted thermal power, set by stellar luminosity, orbital distance, and albedo.
Eris (dwarf planet)
Eris is a dwarf planet in the scattered disk beyond Neptune and the most massive known. Its 2005 discovery led the IAU to reclassify Pluto in 2006.
Ersa
Ersa (Jupiter LXXI, S/2018 J1) is a tiny outer prograde moon of Jupiter discovered by Scott S. Sheppard, announced 2018, named 2019 for the Greek goddess of dew, daughter of Zeus and Selene, sister of Pandia, radius about 1.5 km.
Europa (moon)
Europa (Jupiter II) is Jupiter's smallest Galilean moon, an icy body about 90 percent the size of Earth's Moon that likely holds a global salty ocean beneath its ice.
Exoplanet magnetic field
An exoplanet magnetic field is the global magnetic field generated inside a planet orbiting a star other than the Sun, first directly detected via radio bursts from Beta Pictoris b in the mid-2020s.
Exosphere
The exosphere, also known as the exoatmosphere, is the outermost layer of a planet's atmosphere, where atoms travel without colliding and the fastest escape into space.
Fifth Giant
The Fifth Giant, or hypothetical fifth giant planet, is a proposed ice giant ejected into interstellar space by Jupiter during the Solar System's instability phase.
Filament eruption
A filament eruption is the sudden ejection of a solar filament, cool dense plasma held above the Sun by magnetic fields, into space or the solar atmosphere.
Francisco (moon)
Francisco, designated Uranus XXII, is a small, dark retrograde moon of Uranus discovered in 2001, about 22 km across and the innermost of its irregular satellites.
Galilean moons
The Galilean moons, also called the Galilean satellites or Medicea Sidera, are Jupiter's four largest moons, Io, Europa, Ganymede, and Callisto, discovered by Galileo Galilei in January 1610 and believed to hold subsurface oceans.