Types of Celestial Bodies
According to the accepted modern theory, the objects in the Solar System are segmented into three distinct classifications: planets, dwarf planets and other small bodies. Each of these are defined by the International Astronomical Union.
In order for a body to be classified as a planet, it must maintain three specific criteria. First, it must be in orbit around the Sun. Second, it must contain enough mass to have formed into a spherical shape. A planet must also have cleared its orbital neighborhood of all other objects, with the exception of moons and orbital rings. By this definition, the Solar System only possesses eight known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
When Pluto was redacted from the planetary list due to its small size and highly eccentric orbit, it created an uproar within the scientific community. Now designated a dwarf planet or plutoid, Pluto is joined by other objects that fit the criteria of maintaining orbit around the Sun and being large enough to be spherical. The major ones include Ceres, Haumea, Makemake, Eris, Sedna, Orcus and Quaoar. Even so, the California Institute of Technology estimates there are thousands more.
Any other object in orbit around the Sun is simply a small celestial body. These include asteroids, meteors and satellites.