PRAGUE, Aug 18: The world’s leading astronomers are preparing to reshape our understanding of the solar system in a galactic big bang that would admit three new planets but downgrade distant Pluto.

For decades children around the world have been taught that there are nine planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

But there have been suggestions that Pluto, the smallest and furthest away, no longer merits its place on the list with the discovery in recent years of other, larger asteroids.

Now the International Astronomical Union (IAU) is proposing a new definition of the word ‘planet’ to take into account the most recent scientific discoveries.

Iwan Williams, president of the IAU’s planet definition committee, said that with around 200,000 asteroids already identified there was “a need to rationalize, a need to say where we are”.

To resolve the debate, the IAU is proposing a new definition that would distinguish planets from what it calls “small solar system bodies” — comets and asteroids that orbit the sun — and divide them into categories.

Those discovered before 1900 would be called simply “planets” while a new sub-category of “plutons” would be introduced as a compromise between those who want to banish Pluto from the planetary club and those who want its status maintained.

The move would result in three new “pluton” planets being created along with Pluto: Pluto’s moon, Charon; Ceres, an asteroid that for several decades after its discovery was described as a planet, and the so-called “object 2003 UB313”, which was discovered in 2003.—AFP