A celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite. It has to have sufficient [..]

A secondary category of planets, but not actually. Dwarf planets are bodies of rock that orbit the Sun and are too small to classify as a planet. The Dwarf planets in our solar system as of this defin [..]

celestial body that is nearly spherical but does not meet other definitions for a planet.

A celestial body within the solar system that shares the characteristics of planets. It orbits the Sun, is not a moon, and has a spherical or nearly spherical shape. Unlike a planet, however, a dwarf [..]

A celestial body within the solar system that shares the characteristics of planets. It orbits the Sun, is not a moon, and has a spherical or nearly spherical shape. Unlike a planet, however, a dwarf [..]

A new class of planets, of which there are three: Pluto, Ceres, and Eris.

An object orbiting the Sun that is large enough to be rounded by its own gravity but is not gravitationally dominant in its orbital area and is not a moon. There are currently five recognized dwarf pl [..]

A celestial body that is similar to a planet, but its gravitational pull is too weak to clear all debris from its orbit path (Lesson 30)

The third planet from the Sun and one of four terrestrial planets in the inner solar system. Earth, the only planet where water exists in large quantities, has an atmosphere capable of supporting myriad life forms. The planet is 150 million kilometers (93 million miles) away from the Sun. Earth has one satellite “the Moon.”

A celestial body within the solar system that shares the characteristics of planets. It orbits the Sun, is not a moon, and has a spherical or nearly spherical shape. Unlike a planet, however, a dwarf planet has not cleared away any loose cosmic rubble from its orbit. Dwarf planets include Ceres, Pluto, and Eris.