Ceres (also referred to as (1) Ceres or 1 Ceres) is a dwarf planet of the solar system, the smallest of the three currently acknowledged as so and the only one located in the main asteroid belt. Discovered on January 1st 1801 by Italian astronomer Giuseppe Pazzi, who thought it was the missing planet between Mars and Jupiter, it has a diameter of 950 km and is by far the largest and heaviest object of the main belt, amounting one third of the total mass of the asteroids. It was named after Ceres, Roman goddess of growing plants and motherly love.
Piazzi initially named it Cerere Fernandinea, after the goddess Ceres and the king Ferdinand III of Sicily. The latter part of the name, however, was deemed unacceptable to other nations of the world, and therefore was dropped. The Greeks name it Δήμητρα (Demetra or Demeter), of the name of the corresponding Greek divinity; it shouldn't be confused with English 1108 Demeter, an asteroid.
Ceres has been considered a planet for a while following its discovery (so were 2 Pallas, 3 Juno and 4 Vesta) before being classified as an asteroid for over 150 years. Its status changed once more in 2006, as it became a dwarf planet.
It was confirmed in 2001 by the Hubble space telescope that Ceres was nearly spherical. Its mass and size are close be be enough for hydrostatical equilibrium. The surface of Ceres is thought to be relatively warm, with peek calculated temperatures of -38 degrees Celsius (235 K). Ceres is considered to have a differentiated interior, with a rocky core overlain by an icy mantle of 120 to 60 km, which could contain more fresh water than the Earth does. The dwarf planet might also have a thin atmosphere and frost; it has yet to be proved, however.