1. Is in orbit around the Sun.
2. Has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
3. Has cleared the neighborhood around its orbit.
This definition was specifically created to address the status of Pluto, which no longer met the third criterion after the discovery of Eris and other large objects in the Kuiper belt.
Therefore, as of 2006, the following celestial bodies were considered planets:
* Mercury
* Venus
* Earth
* Mars
* Jupiter
* Saturn
* Uranus
* Neptune
Pluto was reclassified as a dwarf planet along with Eris, Ceres, Makemake, and Haumea.
