The first asteroid to be discovered, found by Giuseppi Piazzi from Palermo, Sicily, on 1 January 1801. It is by far the largest asteroid, 913 km (567 miles) in diameter, and its orbit lies in the main asteroid belt at a distance of 2.77 AU from the Sun. Its mass of 1.17x1021 is about one-third the entire mass of theasteroid belt. It reaches a maximum magnitude of 6.9, its albedo being only 9 per cent. Ceres rotates in just over 9 hours during which time its colour and brightness vary only slightly, suggesting that it is almost spherical and uniformly grey. Information from its spectrum indicates that the surface may be similar in composition to the carbonaceous chondrite meteorites.
