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 in 1846, it was first seen in 2003 - but important details have only now been confirmed.
Designated 2003 UB313, it is about 3,000km across - a world of rock and ice and somewhat larger than Pluto.
previous reports from the BBC:
Large World found near Pluto 03/07/01
New world found far beyond Pluto 03/03/04
The discovery of a new planet in our Solar System could have an unintended consequence - the elimination of Pluto in the list of planets everyone has in their heads. Is it time to wave this distant, cold, dark piece of rock farewell?
[...]in the late 1960s scientists found that Pluto's size had been over-estimated.
It was first thought to be around as large as Earth, whereas accepted thought now suggests that the planet's mass is only around a fifth of the moon's.
"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," says David Rabinowitz of Yale University, who was among the astronomers who discovered 2003 UB313 two years ago.[...]