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Italian astronomer Giuseppe Piazzi discovered Ceres on January 1, 1801 at Palermo. He classified it as a planet, but then it was demoted to an asteroid in the 1850s when other objects in similar orbits were discovered. In 2006, it was promoted as a dwarf planet, a classification it shares with Pluto that is 14 times more massive.
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Ceres was named after the Roman God of agriculture, who is also known as Demeter in Greek mythology. Originally Piazzi named the dwarf planet Cerere Ferdinandea, however it was changed after there were objections to Ferdinandea from other countries.
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It completes its orbit once every 4.6 Earth years and completes a full rotation every nine hours and four minutes. The distance it travels during its orbit is 413,700,000 kilometers.
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Unlike other members of the asteroid belt, Ceres is round and it is large enough for gravity to mold its shape into a sphere.
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Ceres was the first dwarf planet to receive a visit from a spacecraft. In 2015, NASA's unmanned spacecraft Dawn was the first ever to explore a dwarf planet. Dawn approached and orbited Ceres, sending scientific data and detailed images back to Earth. During this mission, Dawn also completed a survey mission to the protoplanet Vesta.
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Ceres is believed to have a rocky core, an icy inner mantle that is 100-kilometers-thick, possibly some subsurface liquid water and a dusty top layer. Scientists have calculated that this ice mantle may contain as much as 200 million cubic kilometers of water which is more fresh water than can be found on Earth.
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Astronomers have discovered direct evidence of water on the Ceres in the form of vapor plumes erupting into space, possible from volcano-like ice geysers on its surface. With that evidence, it is believed Ceres may harbor a subsurface ocean which might be capable of supporting life as we know it, however discussions about life on Ceres are not as active as those for Europa and Mars.
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Astronomers also found two bright spots at about 19 degrees north latitude in a crater on Ceres. It is not believed that they are volcanic in origin. The bright spots indicate a material that is highly reflective and researchers believe it may be ice or salts.
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In 2014, it was confirmed by the Herschel space telescope that Ceres may has an atmosphere with water vapor.
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It is possible that Ceres is a surviving protoplanet (planetary embryo) which formed 4.57 billion years ago in the asteroid belt.
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