Ceres as seen by Hubble Space Telescope(ACS). The contrast has been enhanced to reveal surface details.
|Discovered by||Giuseppe Piazzi|
|Discovery date||1 January 1801|
|MPC designation||1 Ceres|
|Alternative names||A899 OF; 1943 XB|
|Minor planet category||
|Aphelion||2.9765 AU (445,280,000 km)|
|Perihelion||2.5570 AU (382,520,000 km)|
|Semi-major axis||2.7668 AU (413,910,000 km)|
|Orbital period||4.60 yr
|Synodic period||466.7 d
|Average orbital speed||17.882 km/s|
|Inclination||10.593° to Ecliptic
9.20° to Invariable plane
|Longitude of ascending node||80.3276°|
|Argument of perihelion||72.2921°|
|Proper orbital elements|
|Proper semi-major axis||2.7670962 AU|
|Proper mean motion||78.193318 deg / yr|
|Proper orbital period||4.60397 yr
|Precession ofperihelion||54.070272 arcsec / yr|
|Precession of theascending node||−59.170034 arcsec / yr|
|Equatorial radius||487.3 ± 1.8 km|
|Polar radius||454.7 ± 1.6 km|
|Surface area||2,850,000 sq km|
9.43 ± 0.07×1020 kg0.00015 Earths
|Mean density||2.077 ± 0.036 g/cm3|
|Equatorial surface gravity||0.27 m/s2
|Escape velocity||0.51 km/s|
|Sidereal rotation period||0.3781 d
|Axial tilt||about 3°|
|North poleright ascension||19 h 24 min
|Albedo||0.090 ± 0.0033 (V-band geometric)|
|Apparent magnitude||6.64 to 9.34|
|Absolute magnitude(H)||3.36 ± 0.02|
|Angular diameter||0.854" to 0.339"|
Ceres, minor-planet designation 1 Ceres, is the largest asteroid and the only dwarf planet in the inner Solar System, orbiting in the asteroid belt between the orbits of Mars and Jupiter. It is a rock–ice body 950 km (590 mi) in diameter and the smallest identified dwarf planet. It contains about one-third of the aggregate mass of the whole asteroid belt. Discovered on 1 January 1801 by Giuseppe Piazzi, it was the first asteroid to be identified, though it was classified as a planet at the time. It is named after Ceres, the Roman goddess of growing plants, the harvest, and motherly love.
The surface of Ceres is probably a mixture of water ice and various hydrated minerals such as carbonates and clay minerals. It appears to be differentiated into a rocky core and icy mantle, and may harbor an ocean of liquid water under its surface. From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, and hence even at its brightest it is still too dim to be seen with the naked eye except under extremely dark skies.
The unmanned Dawn spacecraft, launched on 27 September 2007 by NASA, is expected to be the first to explore Ceres after its scheduled arrival there in February 2015. After having orbited asteroid 4 Vesta since July 2011, the spacecraft departed for Ceres in September 2012.
On 22 January 2014, ESA scientists reported the detection of water vapor on Ceres. This first definitive detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because althoughcomets are typically considered to "sprout jets and plumes", asteroids do not generally exhibit such features.