It's icy, rocky and bigger than Pluto and, according to scientists who found it orbiting the Sun, it's the newest planet in our solar system.
It is the farthest-known object in the solar system - currently 14,4 billion kilometres away from the Sun, or about three times Pluto's current distance from the Sun.
"This is the first object to be confirmed to be larger than Pluto in the outer solar system," Michael Brown, a planetary scientist at the California Institute of Technology, said at the weekend in a telephone briefing announcing the discovery.
Brown labelled the object as a 10th planet, but there are scientists who dispute the classification of Pluto, the ninth and furthest planet from the sun, as a planet.
Astronomers do not know the new planet's exact size, but its brightness shows that it is at least as large as Pluto and could be up to one and a half times bigger.
Brown has submitted a name for the new planet to the International Astronomical Union, which has yet to act on the proposal, but he did not release the proposed name on Friday.
The briefing was hastily arranged after Brown received word that a secure Website containing the discovery had been hacked and the hacker had threatened to release the information.
Brown and colleagues Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University first photographed the object in 2003 using a 122cm telescope at the Palomar Observatory. It was so far away that its motion was not detected until data was analysed again this past January. It will take at least six months before astronomers can determine its exact size.
Return to internet news headlines
View Internet News Archive