New Member of the Solar System Discovered

Object Is a Cross Between a Minor Planet and a Comet

Aug 25, 2008

The new solar system object named 2006 SQ372 is spotted on its 22,500-year-long orbit around the sun.

The Sloan Digital Sky Survey, a multinational project that maps huge swaths of the night sky, has discovered a new object within our own solar system. The object, currently named 2006 SQ372, is presently at about two billion miles distant from Earth, which would place it slightly closer than the planet Neptune. 2006 SQ372 is near the closest point to the sun in its orbit, a path that takes it 150 billion miles out. This orbit is 1,600 times the distance from the Earth to the sun, or 1600 AU.

2006 SQ372's elliptical orbit is four times longer than it is wide. Another solar system object with a similar orbit is Sedna, a dwarf planet that was discovered in 2003. The new object's orbit is much larger, though, taking it one-and-a-half times farther from the sun and taking twice as long to complete a circuit. 2006 SQ372 is also smaller than the earlier-discovered Sedna. Sedna spans approximately 1,000 miles across compared to the new object's 30-60 miles across.

University of Washington astronomer Andrew Becker led the discovery team. He compares the new object to familiar old solar system objects. "It's basically a comet, but it never gets close enough to the sun to develop a long, bright tail of evaporated gas and dust," he says. Scientists believe that 2006 SQ372 came from the inner edge of the Oort Cloud. The Oort Cloud is a hypothesized well of icy, asteroid-like bodies that are occasionally knocked in close to circle around the sun.

How 2006 SQ372 Was Found

The Sloan Digital Sky Survey scanned the same long swath of sky every cloudless night in 2005, 2006, and 2007. A special computer algorithm was applied to the images to discover the new object. Objects that could be detected moving from night to night had to be in our solar system. Anything further out would not change position noticeably in that short period of time.

The only reason 2006 SQ372 was bright enough to find was because it was so close to the sun. It takes 22,500 years to complete an orbit around the sun, so it just happened to be in the vicinity to be detected as the Sloan Digital Sky Survey was making its scan.

"There are bound to be many more objects like this waiting to be discovered by the next generation of surveys, which will search to fainter levels and cover more area," says Becker. "In a decade, we should know a lot more about this population than we do now."

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