Ceres is a dwarf planet and the largest astronomical object in the asteroid belt, region of the Solar System that lies between the orbits of Mars and Jupiter. Its diameter of approximately 945 km makes it the thirty-third largest known object in the Solar System. Its mass is estimated to be one third of the total mass of the asteroid belt, being the only object in the asteroid belt that has reached hydrostatic equilibrium. Viewed from Earth, its apparent magnitude ranges from 6.7 to 9.3. It was discovered on January 1, 1801 by Giuseppe Piazzi from the Palermo Observatory and is named after Ceres, the Roman goddess of agriculture, harvests and fertility. It was originally considered a planet, but was listed as an «asteroid» in the 1850s, following the discovery of Neptune (1846) and when other objects in similar orbits began to be discovered. In 2006, after the definition of «planet», it was reclassified as a dwarf planet. Ceres was visited by the Dawn probe between March 2015 and October 2018.
