August 21, 2008

Huge Comet Discovered

huge comet-like object has been spotted inside the orbit of Neptune. The
object, at least 30 miles wide, is on the return leg of a 22,500-year journey
around the sun, astronomers announced today.

as 2006 SQ372, the interloper is just over two billion miles (3.2 billion km) from
Earth, though its elongated trek takes it to a distance of 150 billion miles (241
billion km), or nearly 1,600 times the distance from the Earth to the sun.

only known object with a comparable orbit is Sedna --
a distant, Pluto-like dwarf planet discovered in 2003. But 2006 SQ372's travels
take it more than 1.5 times farther from the sun. Its diameter is estimated at 30
to 60 miles (50 to 100 km).

basically a comet,
but it never gets close enough to the sun to develop a long, bright tail of
evaporated gas and dust," said Andrew Becker of the University of
Washington. Comet tails form when solar energy boils material off a comet.

object is not a threat to Earth, which is good. A comet that size would cause
global devastation. The space rock that contributed to the demise
of dinosaurs
65 million years ago was about 6 miles (10 km) wide. The comet
, which put on a spectacular display in the late 1990s, is about 31
miles (50 km) in diameter. Yet many comets are just a mile or two wide.

team found 2006 SQ372 by applying a computer searching algorithm to data taken from
the Sloan Digital Sky Survey II (SDSS II), which is tasked with finding supernova
explosions billions of light-years away to measure the expansion of the
universe. In the survey, the Apache Point Observatory telescope scanned the
same long stripe of sky, an area 1,000 times larger than the full moon in the
sky, every clear night in the fall of 2005, 2006 and 2007.

to how 2006 SQ372 got its unusual orbit, University of Washington graduate
student Nathan Kaib, another member of the discovery team, has some ideas based
on his computer simulations of the object.

could have formed, like
, in the belt of icy debris beyond Neptune, then been kicked to large
distance by a gravitational encounter with Neptune or Uranus," Kaib said.
"However, we think it is more probable that SQ372 comes from the inner
edge of the Oort Cloud."

Oort Cloud is a huge spherical cloud surrounding the solar system. It extends about
18 trillion miles (30 trillion kilometers) from the sun and was first proposed
in 1950 by Dutch astronomer Jan Oort.

discovery was reported today in Chicago, at an international symposium titled "The
Sloan Digital Sky Survey: Asteroids to Cosmology." The researchers plan to
submit details of the finding for publication in the Astrophysical Journal.