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Definition: Ceres from Philip's Encyclopedia

Largest asteroid and the first to be discovered (January 1, 1801, by Guiseppe Piazzi). Ceres' diameter measures 913km (567mi). It orbits in the main asteroid belt, at an average distance from the Sun of 414 million km (257 million mi), the distance of the 'missing' planet predicted by Bode's law.

Summary Article: Ceres, in astronomy
From The Columbia Encyclopedia

(sîr'ēz), in astronomy, a dwarf planet, the first asteroid to be discovered. It was found on Jan. 1, 1801, by G. Piazzi. He took three distinct observations; on the basis of these the mathematician Gauss calculated Ceres' orbit with such accuracy that it was found one year later within 0.5° of the predicted position. Ceres is the largest and most massive of the asteroids; it has a diameter of c.590 mi (949 km) and a mass 1/100,000 that of the earth. Its orbit has a semimajor axis of 2.78 astronomical units and a period of 1,681 days. From its discovery until the 1850s, when many additional asteroids began to be identified, Ceres was regarded by many astronomers as a planet. In 2006 the reconsideration by astronomers of Pluto's status as a planet also led to the reclassification of Ceres as a dwarf planet. The NASA space probe Dawn went into orbit around Ceres in 2015; it revealed the presence of ice and possibly underground liquid or slushy water.

The Columbia Encyclopedia, © Columbia University Press 2018

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