Astronomers claim discovery of ‘10th planet’

AMERICAN scientists have discovered what they are excitedly claiming - but others dispute - should be recognised as the 10th planet in orbit around our sun.

The discovery will focus new attention on the groundbreaking work of the Irish astronomer and engineer Kenneth Essex Edgeworth, from Streete in Co Westmeath.

It is the largest object found in the Kuiper-Edgeworth Belt, a collection of material orbiting the sun beyond Neptune. Edgeworth predicted the existence of the Kuiper Belt in 1943.

But the discovery threatens to further jeopardise little Pluto’s credibility as a planet at all.

Half as big again as Pluto and twice as far away, the new body - designated 2003 UB313 - is almost 15 billion kilometres from the sun, which it orbits every 560 years at a 45-degree angle.

It was first spotted in 2001 but was so far away that its motion was not detected until the scientists re-analysed the data in January this year.

Its discoverers are California Institute of Technology astronomer Michael Brown and colleagues Chad Trujillo, of the Gemini Observatory, in Hawaii, and David Rabinowitz, of Yale University.

Like Pluto, the object’s surface is believed to be predominantly methane, but its size - about 2,700 kilometres in diameter - qualifies it as a planet, Mr Brown said. Earth is about 12,700 kilometres in diameter.

They have submitted a name for the planet to the International Astronomical Union.

“We hope that it’s fairly non-controversial among those who believe Pluto is a planet,” Mr Brown said. “I would say, get out your pens and start rewriting the textbooks today.”

But a debate is underway over just how many planets are in this solar system.

Depending on how this unravels, the number of solar system bodies accepted as planets could shrink to eight, excluding Pluto - or expand to 23 or 24 or more.