Dwarf Planets

Eris Discovery Images [Mike Brown, CalTech]

In 2006, the International Astronomical Union, faced with the prospect of discovery of other larger than Pluto objects, decided to establish another category of Solar System objects: Dwarf Planets. Pluto was assigned to this category, along with Eris, the most massive body to be discovered in the Solar System in 150 years.

Dwarf planets:

orbit the Sun,
have sufficient mass for their self-gravity to overcome rigid body forces so that they assumes a near-spherical shape,
have not cleared the neighbourhood in the vicintiy of their orbits
are not satellites of other bodies.

As of August 2007, only three dwarf planets have been recognised: Eris, Pluto and Ceres.

The Tenth Planet
A set of pages assembled in July 2005, detailing the discovery of an outer solar system object larger than Pluto.
Mike Brown discusses the discovery of Eris
List of Dwarf Planets and Candidates

Links to external sites

Last updated: 15th August 2007
Michael Gallagher