Smallest dwarf planet

The smallest solar system body to be classified as a dwarf planet by the International Astronomical Union (IAU) is Ceres, a 939.4-km-wide (583.71-mile) body located in the main asteroid belt between Jupiter and Mars. Ceres has a mass of 9.4 x 10^20 kg, meaning that it represents around 25% of the total mass of the asteroid belt on its own. It is also the only object in the asteroid belt known to have been rounded by its own gravity.

To be classified as a Dwarf Planet, a body has to meet three key criteria. The first is that it must orbit the sun (it can't be the satellite of another Solar System body). The second is that it can't have fully "cleared its neighbourhood" – true planets have enough mass that they have either merged with or deflected away all other bodies in their vicinity. Finally, it must have been pulled into a more or less spherical shape by the force of its own gravity (a state known as hydrostatic equilibrium). There are several possible dwarf planets awaiting confirmation including one, 90482 Orcus, which is slightly smaller than Ceres at around 910 km (570 mi).