A definition of "planet" was given by a committee of the International Astronomers Union (IAU) at a conference in Prague, according to media reports Thursday.

Three new planets will be added to the Solar System in line with the definition if voted "yes" by IAU members.

During the 12-day conference, which began on Monday, some 2,500 astronomers and scientists from round the world work to find an internationally accepted definition of what constitutes a planet, and decide whether the small Pluto should keep its status.

The definition seems simple at first glance:

"A planet is a celestial body that has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and is in orbit around a star, and is neither a star nor a satellite of a planet."

The asteroid Ceres, which is round, would be recast as a dwarf planet by the new definition. Pluto would remain a planet, and its moon Charon would be reclassified also as a planet.

But the latter two, due to their small sizes, would be called "plutons," to distinguish them from the eight "classical" planets.

A far-out object, of roughly the similar size as Pluto, known as 2003 UB313 , currently nicknamed Xena, would be called a pluton.

The astronomers and scientists attending the conference are expected to weigh the committee's definition, on which IAU members will vote on Aug. 24.

Xinhua/Agencies