Science News Archive

The New Planet That's Bigger Than Pluto

Measurements of the size of a possible new planet by the astronomer Bertoldi from the University of Bonn in Germany along with co investigators have shown that it is bigger than Pluto. This is really making scientists think about what constitutes a planet. The planet's discovery was only announced last year and so far it doesn't have a name, just a designation - 2003 UB313. Unfortunately the object is so far away that we need to use a few tricks to work out its size and the new measurements have shown it is very cold, about -250 degrees Celsius, and has a size 50% larger than Pluto. Astronomers now have a dilemma because Pluto and UB313 are not alone. Pluto is the smallest planet in our solar system, smaller than our moon and we have recently discovered that it is part of a swarm of objects all about the same distance from the sun as Pluto in a band called the Kuiper Belt. So far we have found 1000 of these objects and UB313 is the only one to be discovered bigger than Pluto, but there could be others. Astronomers are now arguing whether they should call all new findings bigger than Pluto planets or demote Pluto to a non-planet. It's quite a bitter argument and could be raging for a long while but either way we will soon have to rewrite the textbooks because there are no longer nine planets in the solar system.

5th Feb 2006