Scientists believe they have discovered the Solar System's 10th planet. It was found by astronomers using a telescope near San Diego in California, America. The planet has yet to be given a real name by the International Astronomical Union - but at the moment it is called 2003UB313. It was discovered back in January this year but was found on a photograph taken of the sky in October 2003. There have been so many pictures taken for this search that it's taken over a year for the scientists to get round to checking the pictures. 
The new planet (circled) |
Over the last couple of years there have been discoveries of two other objects, Quaoar and Sedna. Both of them are smaller than Pluto and are thought to be asteroids rather than planets. 560 years for one orbit The Earth takes one year to go around the Sun. This new planet is so far away from the Sun - about 97 times further than the Earth - that it takes 560 years for it to complete one orbit. At that distance, if you were to hold a pin at arms length, then the head of the pin would cover the Sun. It's also pretty cold out there too - as there wouldn't be much heat from the Sun, the surface temperature is only likely to be around -243 degrees. Pretty chilly! Half the size of the Moon By looking at the light we receive from this new planet, we can also work out how big it is. It turns out that itβs bigger than Pluto, at about 1,200 km across. That still only makes it about half the size of the Moon though. Anyone wishing to see the new planet will be disappointed. Whilst it is in the skies over Norfolk, large telescopes will be needed to see it and even then it will only appear as a faint spot of light. | 
