Number of planets in solar system drops to 8

The International Astronomical Union (IAU) on Thursday adopted a resolution on planet definition, according to which Pluto had been stripped of the planetary status.

Pluto had been regarded by international astronomers as a planet along with other eight planets since its discovery in 1930.

The decision, made by the IAU at a meeting in Prague, defines a planet as "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

This is the first time that scientists have a formal definition of a planet, which disqualifies Pluto as its oblong orbit overlaps with Neptune's.

Thursday's definition left just eight classical planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The IAU, the world's largest astronomical society, was founded in 1919. It holds its international conference every three years.

Source: Xinhua