"Plutoid" as a name for dwarf planets like Pluto

The International Astronomical Union has decided on the term "plutoid" as a name for dwarf planets like Pluto.

The name plutoid was proposed by the members of the IAU Committee on Small Body Nomenclature (CSBN), accepted by the Board of Division III and by the IAU Working Group for Planetary System Nomenclature (WGPSN), and approved by the IAU Executive Committee at its recent meeting in Oslo, according to a statement released on 11th June, 2008.

Here's the official new definition:

"Plutoids are celestial bodies in orbit around the sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit."

In short:

small round things beyond Neptune that orbit the sun and have lots of rocky neighbors.

The two known and named plutoids are Pluto and Eris. The organization expects more plutoids will be found.

The dwarf planet Ceres is not a plutoid as it is located in the asteroid belt between Mars and Jupiter, according to the IAU. Current scientific knowledge lends credence to the belief that Ceres is the only object of its kind, the IAU stated. Therefore, a separate category of Ceres-like dwarf planets will not be proposed at this time, the reasoning goes.

The term plutoid joins a host of other odd words -- plutinos, centaurs, cubewanos and EKOs -- that astronomers use to define objects in the outer solar system.