It is the first time an object so big has been found in our solar system since the discovery of Pluto 75 years ago.

The announcement, made Friday by Mike Brown of the California Institute of Technology, came just hours after another celestial object slightly smaller than Pluto was revealed, on a very confusing day for astronomers and the media.

The new object, temporarily named 2003 UB313, is about three times as far from the sun as is Pluto.

"It's definitely bigger than Pluto," said Brown, a professor of planetary astronomy at Caltech. The object is round and could be up to twice as large as Pluto, Brown told reporters during a hastily called NASA-run teleconference Friday evening. His best estimate is that it is 2,100 miles (3,360 kilometers) wide, about one-and-a-half times the diameter of Pluto.

The new world is about 97 astronomical units from the sun. An astronomical unit is the distance between the sun and Earth. 2003 UB313 becomes the farthest-known object in the solar system, and the third brightest of the Kuiper Belt objects.