Possible new planet is larger than Pluto-research

By Patricia Reaney

LONDON (Reuters) – A distant object discovered in space
last year which could be the 10th planet in our solar system is
around a third bigger than Pluto, German astrophysicists said
on Wednesday.

They determined the diameter of the potential new planet,
known as 2003 UB313, by measuring its thermal emission.

“We actually measured the size of UB313 which was not known
prior to these observations,” Professor Frank Bertoldi, of the
University of Bonn and the Max Planck Institute for Radio
Astronomy in Germany who headed the research team, said in an
interview with Reuters.

According to their calculations it has a diameter of 3,000
km (1,864 miles), about 700 km (435 miles) bigger than Pluto,
which would make it the largest solar system object found since
the discovery of Neptune in 1846.

“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,” Bertoldi added.

The International Astronomical Union will decide if UB313,
found by Professor Mike Brown and his colleagues at the
California Institute of Technology, is a planet. No date has
been set for a decision.

Although the size of UB313 is known, what it is made of is
not, a factor that is important in determining planet status.

No new planet has been designated since the discovery of
Pluto in 1930.

Brown and his team discovered UB313 by looking for visible
wavelengths in the skies. They determined the orbital shape and
distance of the potential planet, which has been nicknamed Xena
after the warrior princess of television fame, by its speed.

Last October, Brown and his team announced UB313 had a moon
called Gabrielle.

The possible planet, the most distant object seen in the
solar system, is an icy body in the Kuiper Belt beyond Neptune.
The belt contains objects left over from the formation of our
planetary system some 4.5 billion years ago.

Solar system objects are visible through the light they
reflect from the sun. Bertoldi and his team used a 30-meter
(100-ft) telescope in southern Spain and a very sensitive heat
sensor to measure the heat radiation to determine the size.

UB313′s orbit is elongated. It zooms as close as 5.6
billion km (3.5 billion miles) from the sun and moves out to as
far as 14.5 billion km (9 billion miles) away.

Earth orbits consistently at 150 million km (93 million
miles) from the sun. It takes the potential planet 560 Earth
years to complete one trip around the Sun, compared to Pluto’s
250 years.

(Additional reporting by Deborah Zabarenko in Washington)