10th planet discovered in solar system

The solar system has a 10th planet, an astronomer announced Friday. Larger than Pluto, its highly inclined orbit slings it from its closest approach to the sun — 3.3 billion miles out — to its present location in dark, frigid space 9 billion miles away.

It is presently the most distant identified object in the solar system and takes 560 years to complete one orbit. Yet it is relatively big and bright, within the ability of many advanced amateur astronomers to see and photograph.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto — and then what? Soon most sixth-graders may be able to complete the list, but for now, the proposed name of the 10th planet is secret.

Michael Brown of the California Institute of Technology announced the find during a telephone press conference Friday afternoon, in which the Deseret Morning News participated. The research was partly funded by NASA, and the press conference was hosted by the agency's Jet Propulsion Laboratory in Pasadena.

Brown said the planet's name won't be released for a while.

"We have submitted a name to the International Astronomical Union, and I don't want to say what it is yet because we really want this name to get accepted," he said. In the world of science, the protocol is to win official acceptance of a name by a governing group such as the IAU before it is released publicly.

Brown and colleagues Chad Trujillo of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz of Yale University made the discovery Jan. 8 using the 48-inch diameter Samuel Oschin Telescope at Mount Palomar Observatory in California. In a survey for distant objects, they actually had photographed the planet on Oct. 31, 2003, but it was not recognized until recently.

By strange coincidence, two other large, distant objects were announced about the same time. Spanish astronomers announced one on Thursday, and Brown also announced another Friday besides the 10th planet. Brown said his group also had been following the object announced by the Spaniards, and they were able to calculate its size as three-quarters that of Pluto.

All three apparently are members of the Kuiper belt of comet-like material that orbits the sun in the distant solar system. But only the one temporarily designated 2003-UB313 is larger than Pluto.