Dwarf planets are a class of celestial bodies in the solar system defined by the International Astronomical Union (IAU) in Prague on 24 August 2006.
Since 2008, five celestial bodies are officially considered dwarf planets:
However, there are several hundred other dwarf planet candidates in the solar system that could still be classified as dwarf planets.
The dwarf planet category is one of the three following categories defined by the IAU for objects in the Solar System, excluding satellites (Moons):
- A planet is a celestial body that
- is in orbit around the Sun,
- has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
- has cleared the neighbourhood around its orbit
- A “dwarf planet” is a celestial body that
- is in orbit around the Sun,
- has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,2
- has not cleared the neighbourhood around its orbit, and
- is not a satellite.
- All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.