Dwarf Planets


Check definition of Dwarf Planet

What is a Dwarf Planet?

Dwarf Planet is a celestial body resembling a small planet but lacking certain technical criteria that are required for it to be classed as such.

In 2006 the International Astronomical Union (IAU) adopted the term “dwarf planet” for solar system objects that were bigger than small solar system bodies such as comets and asteroids but not quite planets.

The definition of a dwarf planet is 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.

Dwarf Planet Facts:

There are 5 dwarf planets in our solar system: Ceres; Eris, Haumea, Makemake and Pluto.

Dwarf Planets for Kids

Dwarf Planets for Kids


Ceres is the only dwarf planet in the asteroid belt. It has been visited by the Dawn spacecraft.

Ceres is located in the asteroid belt between the orbits of Mars and Jupiter. Ceres was discovered on 1 January 1801. It was discovered well before Pluto and 45 years before Planet Neptune. Ceres was considered a planet for around 50 years before being re-classified as an asteroid and as a dwarf planet in 2006.


Eris was discovered on 5 January 2005. Eris takes 557 Earth years to complete a single orbit around our sun. It was referred to as the tenth planet until it was reclassified in 2006.


Haumea is oddly-shaped and is twice as long as it is wide. It is one of the fastest rotating large objects in our solar system. Haumea was discovered on 28 December 2004.

Makemake was discovered on 31 March 2005. Makemake is the third largest dwarf planet behind Eris and Pluto.


Pluto is considered a true planet until 2006 when astronomers decided it was a dwarf planet.

In 2006 Pluto was demoted from a planet to a dwarf planet by the International Astronomical Union (IAU). Before pluto was demoted it was the ninth planet. This created a controversy amongst astronomers. Most astronomers agreed with the new classifications, however some still preferred to call Pluto a planet due to it historically being a planet.

Eris is the largest dwarf planet. It is only slightly bigger than Pluto. It is about 1160km in diameter.



Dawn spacecraft was the first spacecraft to orbit a dwarf planet. It orbited Ceres on 6 March 2015. New Horizons space probe flew by Pluto and its five moons on 14 Juy 2015.

Possible Dwarf Planets:

Solar system objects that might be considered in the future as dwarf planet include Orcus, Quaoar, 2007 OR10 and Sedna.

Scientists estimate there could be at least 200 dwarf planets in the solar system (including Kuiper Belt and Oort Cloud).

Dwarf Planet Links

Dwarf Planets: Science and Facts About Solar System’s Smaller Worlds: