Icy body find bolsters claims for 10th planet

CLAIMS that the sun has a 10th planet have been bolstered by the discovery that an icy body found on the edge of the solar system is bigger than Pluto.

Astronomers announced the existence of the object, UB313, last summer. Since then, debate has raged over whether it really is a planet or a frozen comet.

The object is one of about 100,000 icy bodies that lie in a ring known as the Kuiper Belt on the outer fringe of the Solar System.

Some Kuiper Belt objects escape into the inner solar system, where they appear as visiting comets.

UB313’s orbit takes it up to 97 times farther from the Sun than the Earth - almost twice as far as Pluto, the solar system’s most remote recognised planet.

When first spotted by astronomers, UB313 appeared to be at least as big as Pluto. But the object’s true size was impossible to calculate without knowing its reflectivity.

German scientists led by Professor Frank Bertoldi from the University of Bonn has solved the problem by measuring the amount of heat radiated by UB313.

They worked out that the object has a diameter of about 3,000km, making it 700km larger than Pluto.

The finding means that UB313 is the largest solar system object to be identified since the discovery of Neptune in 1846.

Prof Bertoldi said: “Since UB313 is decidedly larger than Pluto, it is now increasingly hard to justify calling Pluto a planet if UB313 is not also given this status.”

Astronomers have been logging small planetary objects beyond Neptune and Pluto since 1992.