Most massive dwarf planet

The most massive dwarf planet is Eris, which has an estimated mass of 1.66 x 10^22 kg (16.6 sextillion kg). This makes it marginally larger than the next most massive dwarf planet, Pluto, which has a diameter of 1.30 x 10^22 kg. Pluto is physically larger, however, with a diameter of 2,376.6 km compared with 2,326 km for Eris.

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).