In August 2006, the International Astronomical Union published the official definition of the term "planet," which curiously had no clear meaning and until then had granted that honor to Pluto. The final definition was as follows:
Planet: Any celestial body that meets these characteristics:
(1) Orbit around the Sun
(2) It has enough mass for its gravity to overcome the forces of the rigid body, reaching a hydrostatic equilibrium (practically spherical).
(3) It has cleared the vicinity of its orbit.
This classification left out Pluto, since it did not comply with point (3), since this object is located in an area called Kuiper belt, and in its orbit there are some of these bodies that have not been "swept" by it (that is, it does not have orbital dominance). Thus, the new name "dwarf planet«:
Dwarf planet: It is any celestial body that meets these characteristics:
(1) Orbit around the Sun
(2) It has enough mass for its gravity to overcome the forces of the rigid body, reaching a hydrostatic equilibrium (practically spherical).
(3) It is not a satellite of a planet or other non-stellar body
(4) It has not cleaned the vicinity of its orbit
Additionally, any object that is a dwarf planet and is also a trans-Neptunian object (located beyond the orbit of Neptune) also becomes a Plutoid, an additional category designated by the IAU. Ceres does not qualify as a plutoid since it is located in the Main Asteroid Belt.
Next we will see the current dwarf planets (in order of distance from the Sun):