Solar system '10th planet' is bigger than Pluto

London Telegraph
Feb. 02, 2006

Claims that the Solar System has a 10th planet are bolstered by the announcement today that an icy body at its fringes is bigger than Pluto.

Scientists have made the first accurate measurement of the size of this putative planet, announced last summer, tentatively called 2003 UB313 and nicknamed Xena before it gets an official name.

A group led by Prof Frank Bertoldi from the University of Bonn and Max Planck Institute for Radioastronomy has estimated the size by measuring the tiny amount of heat that the body gives off.

The Bonn team, which is co-led by Wilhelm Altenhoff, was able to determine a diameter of about 1,900 miles, which makes it 440 miles larger than Pluto and the largest solar system object found since the discovery of Neptune in 1846.

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

''The discovery of a solar system object larger than Pluto is very exciting," Mr Altenhoff said. "Maybe we can find even other small planets out there, which could teach us more about how the Solar System formed and evolved."

In the same issue of Nature, Scott Sheppard of the Carnegie Institution of Washington said: "No matter how you look at it, we either have a planet less [drop Pluto] or a planet more [include 2003 UB313] in our Solar System."

The most distant object ever seen in the Solar System, 2003 UB313 has an elongated orbit that takes it up to 97 times farther from the Sun than is the Earth.