An image of Ceres captured with the Hubble Space Telescope.
Ceres, with an official name of “1 Ceres” because it was the very first minor, or dwarf, planet discovered, was discovered January 1, 1801 by Italian Giuseppe Piazzi. It is the smallest known dwarf planet as well as the only one located within the asteroid belt itself. The length across Ceres is very comparable to the size of our very own Texas. Ceres is spherical in shape and like Earth, has denser material at the core and lighter minerals near the surface. With a diameter of about 950 kilometers, Ceres is the largest object in the asteroid belt as well as the most massive with a mass that makes up about 32% of the belt’s total mass. There is excitement surrounding Ceres because Ceres appears to be differentiated into a rocky core and ice mantle (see picture, bottom right). It may harbor an ocean of liquid water underneath its surface, which makes it a potential target of current searches for extraterrestrial life. The surface of Ceres is probably made of a mixture of water ice and various hydrated minerals like carbonates and clays. The hope with Dawn is to look deeper in to this possibility.
Photographic comparison of the size of Ceres with the Earth and Moon