The planet, the farthest-known object in the solar system, is currently nine billion miles 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 in a telephone briefing Friday.
Brown labeled the object as a 10th planet, but there are scientists who dispute the classification of Pluto as such.
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 1 1/2 times bigger. The research was funded by NASA.
As CBS News Correspondent Steve Futterman reports the planet takes 560 years to orbit the sun. Of the discovery, Brown said, I was just on cloud nine. I don't even know how to describe how it was."
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 Friday.