Astronomers in the United States have announced the discovery of the 10th planet to orbit our Sun.
The largest object found in our Solar System since Neptune was discovered in 1846, it was first seen in 2003 but has only now been confirmed as a planet.
Designated 2003 UB313, it is about 3,000km across, a world of rock and ice and somewhat larger than Pluto. Scientists say it is three times as far away as Pluto, in an orbit at an angle to the orbits of the other planets. Astronomers think that at some point in its history, Neptune likely flung it into its highly-inclined 44-degree orbit.
It is currently 97 Earth-Sun distances away - more than twice Pluto's average distance from the Sun.
Its discoverers are Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory in Hawaii, and David Rabinowitz of Yale University.
David Rabinowitz told the BBC News website: "It has been a remarkable day and a remarkable year. 2003 UB313 is probably larger than Pluto. It is fainter than Pluto, but three times farther away. Brought to the same distance from the Sun as Pluto, it would be brighter. So today, the world knows that Pluto is not unique. There are other Plutos, just farther out in the Solar System where they are a little harder to find."
Link: BBC Science.