New 'planet' discovered beyond Pluto

Scientists in the United States were expected to announce today that they had found a new "planet" in our solar system, after spotting a 10th heavenly body orbiting the sun.

After sightings by the Hubble telescope and the Spitzer space telescope, Nasa has announced that it would present the "discovery of the most distant object ever detected orbiting the sun".

The find was made by Dr Michael Brown, associate professor of planetary astronomy at the California Institute of Technology, in Pasadena, who is working on a Nasa-funded project, the organisation said.

The object has been named Sedna, after the Inuit goddess of the ocean.

The body is believed to be about 1,250 miles across, but may even be larger than the furthest known planet, Pluto, which was discovered in 1930 and has a diameter of 1,406 miles.

Scientists believe Sedna is 6.2bn miles from Earth, in a region of space known as the Kuiper Belt, which contains hundreds of other known bodies.

Whether the new discovery can actually be called a planet is likely to be debated by astrophysicists for months or even years to come. Many bodies of rock and ice exist in the region and there is still some argument over whether Pluto is a real planet.