New Pluto-Size Object Discovered in Solar System

July 29, 2005

Astronomers in Spain and the U.S. have discovered a large object skirting the fringes of the solar system. Research teams from both countries announced the discovery separately.

The object, designated 2003 EL61, is about 930 miles (1,500 kilometers) across, according to Mike Brown, an astronomer at the California Institute of Technology, who led the U.S-based team. The team announced its discovery today.

The object also has a moon.

2003 EL61 and its satellite are located in the Kuiper belt, a region beyond Neptune that includes Pluto and the recently discovered large planet-like objects Quaoar and Orcus.

Preliminary reports from the Spanish scientists suggested it may be twice as big as Pluto, but those reports now appear to be incorrect.

"They were just guessing a size, because they didn't know it has a satellite," Brown wrote in an e-mail to National Geographic News.

The astronomers are classifying the newly discovered object as a "scattered Kuiper belt object." Such objects are believed to have had a close encounter with Neptune, which then scattered them with its gravitational force into eccentric orbits.

Awkward Situation

Today's announcement makes for "sort of an awkward situation," said Brian Marsden, director of the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts. There were some early questions about which team would receive credit for the discovery.

Brown's team first noticed the object on May 6, 2004. The team will present details about the find at a conference in Cambridge, England, this September.

The presentation will include measurements of the object's size from new observations made with the Spitzer Space Telescope. The observations were made July 22.

The Spanish group, led by Jose-Luis Ortiz at the Instituto de Astrofísica de Andalucía in Granada, Spain, found the object in images taken in 2003. They announced their discovery Thursday.

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