New minor planet helps explain comets

WASHINGTON (Reuters) - A newly discovered "minor planet" with an elongated orbit around the Sun may help explain the origin of comets, researchers said on Monday.

The object, known as 2006 SQ372, is starting the outward portion of a 22,500-year orbit that will take it 150 billion miles away from the Sun.

The icy lump of rock is just over 2 billion miles from Earth, a bit closer than the planet Neptune, researchers told a symposium on Monday. They will publish their findings in the Astrophysical Journal.

The orbit of 2006 SQ372 is an ellipse four times longer than it is wide, said University of Washington astronomer Andrew Becker, who led the research team. Sedna, a distant, Pluto-like dwarf planet discovered in 2003, is the only other object with a similar orbit, but not nearly as stretched out.

The new object is about 60 miles in diameter. "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," Becker said in a statement.

University of Washington graduate student Nathan Kaib said it is unclear how the object formed, "It could have formed, like Pluto, in the belt of icy debris beyond Neptune, then been kicked a large distance by a gravitational encounter with Neptune or Uranus," Kaib said in a statement.

More likely, he said, it came from the Oort Cloud, a distant reservoir of icy, asteroid-like bodies that orbit the Sun at distances of several trillion miles (km).

"One of our goals is to understand the origin of comets, which are among the most spectacular celestial events. But the deeper goal is to look back into the early history of our solar system and piece together what was happening when the planets formed," Kaib said.

(Reporting by Maggie Fox)