Dwarf planet


A dwarf planet is an object that is not a satellite and by the IAU definition:

  • is in orbit around the Sun
  • has sufficient mass to possess a spheroid-shape
  • has not "cleared the neighbourhood" around its orbit.

Dwarf planets are not 'true' planet only because of the last criterion, which says that a 'true' planet has "cleared the neighbourhood" in its orbital zone, meaning that there exist no objects of substantial mass other than natural satellites near its orbit.


Why isn't Pluto a planet?edit

Pluto was excluded from the IAU definition of a planet due to a redefinition of the criteria for being a planet in 2006. This attracted some controversy after it defined the solar system to have 8 planets instead of 9, however, it is now generally accepted that Pluto is a dwarf planet.