Tuesday, August 19, 2008

Astronomers Find Very Unusual Solar System Minor Planet

Over two billion miles from Earth, inside the orbit of the planet Neptune, a lump of ice and rock is beginning the return leg of a 22,500-year journey to the inner system. Of course "inner system" as it applies to 2006 SQ372, is a relative thing. At it's closest approach to the sun it will be 150 billion miles out, nearly 1,600 times the distance from the Earth to the Sun. So many things are unusual about SQ372. The major planets in the solar system have circular orbits. However SQ372's orbit is four times longer than it is wide. The only known object with a comparable orbit is Sedna -- a Pluto-like dwarf planet. But 2006 SQ372's orbit takes it more than one-and-a-half times further from the Sun, and its orbital period is nearly twice as long. SQ372 is also small, 30-60 miles, making it for all intents a comet, thought one that never gets close enough to develop a tail. That SQ372 is here at all is causing some head scratching. Comets come from the Ortt cloud which contains objects ejected from the inner system. The Ortt objects resides in orbits around the Sun at distances of several trillion miles. However even at its most distant turning point, SQ372 will be ten times closer to the Sun than the main body of the Oort Cloud. Some astronomers have suggested an "inner" Ortt cloud, suggesting that Sedna might also belong to that group. One thing seems to be coming to light though. There are likely many more of these smaller icy bodies in the solar system that will be uncovered by the next series of scans with greater sensitivity and covering a wider area.

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