Discovered by Sicilian astronomer Giuseppe Piazzi on January 1, 1801, Ceres is the largest "asteroid" in the asteroid belt between Mars and Jupiter. It is spherical in shape, and some 580 miles in diameter(930 kilometers). It takes 4.6 years to orbit once in a nearly circular orbit around the Sun.
The classification of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun. Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno and 4 Vesta) for about half a century.
Ceres is the largest object in the asteroid belt, which lies between Mars and Jupiter. The Kuiper belt is known to contain larger objects, including Pluto, its moon Charon, and 136.108 haumea , while more distant Eris, in the scattered disc, is the largest of all these bodies.
The surface composition of Ceres is broadly similar to that of C-type asteroids. However, some differences do exist. The ubiquitous features of the Cererian IR spectra are those of hydrated materials, which indicate the presence of significant amounts of water in the interior. Other possible surface constituents include iron-rich clays (crostedtite) and carbonate minerals (dolomite and siderite), which are common minerals in carbonaceous chondrite meteorites. The spectral features of carbonates and clay are usually absent in the spectra of other C-type asteroids. Sometimes Ceres is classified as G-type asteroid.
The Cererian surface is relatively warm. The maximum temperature with the Sun overhead was estimated from measurements to be 235 K (about −38 °C) on 5 May 1991.
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