Ceres

/sear"eez/, n.

1. a pre-Roman goddess of agriculture under whose name the Romans adopted the worship of the Greek goddess Demeter.

2. Astron. the first asteroid to be discovered, being the largest and one of the brightest.

3. a town in central California. 13,281.

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I

In Roman religion, the goddess of the growth of food plants, sometimes worshiped in association with the earth goddess Tellus.

Her cult was overlaid by that of Demeter, who was worshiped in Greece and Sicily. According to tradition, her cult was introduced into Rome in 496 BC to check a famine. Her temple on Aventine Hill was known as a centre of plebeian religious and political activities and for its artwork.

Ceres, Classical sculpture; in the Vatican Museum.

Alinari/Art Resource, New York

II

Largest known asteroid in the solar system and the first discovered, in 1801.

Named after the Roman goddess Ceres, it revolves around the Sun in 4.6 Earth years and is about 575 mi (925 km) across.

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▪ Roman goddess

 in Roman religion, goddess of the growth of food plants, worshiped either alone or in association with the earth goddess Tellus. At an early date her cult was overlaid by that of Demeter (q.v.), who was widely worshiped in Sicily and Magna Graecia. On the advice of the Sibylline Books, a cult of Ceres, Liber (Liber and Libera), and Libera was introduced into Rome (according to tradition, in 496 BC) to check a famine. The temple, built on the Aventine Hill in 493 BC, became a centre of plebeian religious and political activities and also became known for the splendour of its works of art. Destroyed by fire in 31 BC, it was restored by Augustus. The three chief festivals of Ceres' cult all followed Greek lines.

▪ dwarf planet

  dwarf planet and largest known asteroid in the asteroid belt and the first asteroid to be discovered. Ceres was found, serendipitously, by the Italian astronomer Giuseppe Piazzi (Piazzi, Giuseppe) of the Palermo Observatory on Jan. 1, 1801. Additional observations of the object by Piazzi were cut short by illness, but Ceres was recovered on Jan. 1, 1802, by the German Hungarian astronomer Franz von Zach (Zach, Franz Xaver, Freiherr von), using an orbit calculated by the German mathematician Carl Friedrich Gauss (Gauss, Carl Friedrich). Ceres was named after the ancient Roman grain goddess and the patron goddess of Sicily, thus beginning a long-standing tradition of naming main-belt asteroids after female characters from Greco-Roman mythology.

      Ceres revolves around the Sun once in 4.61 Earth years in a nearly circular, moderately inclined (10.6°) orbit at a mean distance of 2.77 astronomical units (AU; about 414 million km [257 million miles]). Although it—and the next two asteroids discovered, Pallas and Juno—are located near the distance predicted by Bode's law for the “missing” planet between Mars and Jupiter, most asteroids found subsequently are not so located, and so the agreement with this “law” appears to be coincidental.

      Ceres has the shape of a flattened sphere with an equatorial radius of 490 km and a polar radius of 455 km, equivalent in volume to a sphere with a diameter of 940 km—i.e., about 27 percent that of Earth's Moon. Although Ceres is the largest asteroid, it is not the brightest. That honour belongs to the second largest asteroid, Vesta, which orbits closer to the Sun than Ceres (Vesta's mean distance is 2.36 AU) and has a surface reflectivity more than three times as high (its albedo is 0.34, compared with 0.10 for Ceres). The mass of Ceres, which accounts for more than one-third the total mass of the main asteroid belt, is about 9.1 × 10²⁰ kg, and its density is 2.2 grams per cubic cm (about two-thirds that of the Moon). Ceres's shape and density are consistent with a two-layer model of a rocky core surrounded by a thick ice mantle. Ceres rotates once in 9.1 hours, showing no large-scale colour or brightness variations over its surface. Compositionally, the asteroid's surface resembles the carbonaceous chondrite meteorites.

      Ceres was designated a dwarf planet, a new category of solar system objects defined in August 2006 by the International Astronomical Union. For a discussion of that decision, see planet.

Edward F. Tedesco

 

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