[meteorite-list] Astronomers Find an Unusual New Denizen of the Solar System

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 19 Aug 2008 17:19:50 -0700 (PDT)
Message-ID: <200808200019.RAA14201_at_zagami.jpl.nasa.gov>

Sloan Digital Sky Survey

Contacts:

Andrew Becker, University of Washington
206-685-0542

Nathan Kaib, University of Washington
206-375-1048

David Weinberg, SDSS-II Spokesperson, Ohio State University
614-406-6243

Jordan Raddick, SDSS Public Information Officer, Sloan Digital Sky Survey
443-570-7105

August 18, 2008

See you again in 22,000 years

Astronomers find an unusual new denizen of the Solar System

CHICAGO -- A "minor planet" with the prosaic name 2006 SQ372 is just over
two billion miles from Earth, a bit closer than the planet Neptune. But this
lump of ice and rock is beginning the return leg of a 22,500-year journey
that will take it to a distance of 150 billion miles, nearly 1,600 times the
distance from the Earth to the Sun, according to a team of researchers from
the Sloan Digital Sky Survey (SDSS-II).

The discovery of this remarkable object was reported today in Chicago, at an
international symposium titled "The Sloan Digital Sky Survey: Asteroids to
Cosmology." A paper describing the discovery technique and the properties of
2006 SQ372 is being prepared for submission to The Astrophysical Journal.

The orbital paths of the major planets are nearly circular, but the orbit of
2006 SQ372 is an ellipse that is four times longer than it is wide, said
University of Washington astronomer Andrew Becker, who led the discovery
team. The only known object with a comparable orbit is Sedna -- a distant,
Pluto-like dwarf planet discovered in 2003 -- 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.

The new object is much smaller than Sedna, Becker said, probably 30-60 miles
across instead of nearly 1,000. "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's team found 2006 SQ372 by applying a specialized computer searching
algorithm to data taken for a completely different purpose: finding
supernova explosions billions of light years away to measure the expansion
of the universe. The SDSS-II supernova survey scanned the same long stripe
of sky, an area 1,000 times larger than the full moon, every clear night in
the fall of 2005, 2006, and 2007.

"If you can find things that explode, you can also find things that move,
but you need different tools to look for them," said team member Lynne
Jones, also of the University of Washington. The only objects close enough
to change position noticeably from one night to the next are in our own
solar system, Jones explained.

SQ372 was first discovered in a series of images taken between September 27
and October 21, 2006. Team member Andrew Puckett, of the University of
Alaska Anchorage, then searched the supernova survey's Fall 2005
observations to find earlier detections, thus securing the discovery.
Subsequent SDSS detections of SQ372 have been found in data from the 2006
and 2007 observing seasons.

University of Washington graduate student Nathan Kaib, another member of the
discovery team, has been running computer simulations to try to understand
out how 2006 SQ372 might have acquired its unusual orbit. "It could have
formed, like Pluto, in the belt of icy debris beyond Neptune, then been
kicked to large distance by a gravitational encounter with Neptune or
Uranus," said Kaib. "However, we think it is more probable that SQ372 comes
from the inner edge of the Oort Cloud."

In 1950, Kaib explained, the Dutch astronomer Jan Oort hypothesized that
most comets come from a distant reservoir of icy, asteroid-like bodies,
which were ejected from the inner solar system by gravitational kicks from
the giant planets as the planets themselves were forming four and a half
billion years ago. Most objects in the Oort cloud orbit the Sun at distances
of several trillion miles, but the gravity of passing stars can alter their
orbits, flinging some into interstellar space and deflecting others to the
inner solar system where they "light up" as comets.

Even at its most distant turning point, 2006 SQ372 will be ten times closer
to the Sun than the supposed main body of the Oort Cloud, said Kaib. "The
existence of an 'inner' Oort cloud has been theoretically predicted for many
years, but SQ372 and perhaps Sedna are the first objects we have found that
seem to originate there. It's exciting that we are beginning to verify these
predictions."

Becker noted that 2006 SQ372 was bright enough to find with the SDSS only
because it is near its closest approach to the Sun, and that the SDSS-II
supernova survey observed less than one percent of the sky. "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," said Becker. "In a decade, we should know a lot more about this
population than we do now."

"One of our goals," said Kaib, "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."

About the Sloan Digital Sky Survey (SDSS)

The Sloan Digital Sky Survey is the most ambitious survey of the sky ever
undertaken, involving more than 300 astronomers and engineers at 25
institutions around the world. SDSS-II, which began in 2005 and finished
observations in July, 2008, is comprised of three complementary projects.
The Legacy Survey completed the original SDSS map of half the northern sky,
determining the positions, brightness, and colors of hundreds of millions of
celestial objects and measuring distances to more than a million galaxies
and quasars. SEGUE (Sloan Extension for Galactic Understanding and
Exploration) mapped the structure and stellar makeup of the Milky Way
Galaxy. The Supernova Survey repeatedly scanned a stripe along the celestial
equator to discover and measure supernovae and other variable objects,
probing the accelerating expansion of the cosmos. All three surveys were
carried out with special purpose instruments on the 2.5-meter telescope at
Apache Point Observatory, in New Mexico.

Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan
Foundation, the Participating Institutions, the National Science Foundation,
the U.S. Department of Energy, the National Aeronautics and Space
Administration, the Japanese Monbukagakusho, the Max Planck Society, and the
Higher Education Funding Council for England. The SDSS Web Site is
     http://www.sdss.org/

SDSS is managed by the Astrophysical Research Consortium for the
Participating Institutions. The SDSS-II Participating Institutions are the
American Museum of Natural History, Astrophysical Institute Potsdam,
University of Basel, University of Cambridge, Case Western Reserve
University, University of Chicago, Drexel University, Fermilab, the
Institute for Advanced Study, the Japan Participation Group, Johns Hopkins
University, the Joint Institute for Nuclear Astrophysics, the Kavli
Institute for Particle Astrophysics and Cosmology, the Korean Scientist
Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National
Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the
Max-Planck-Institute for Astrophysics (MPA), New Mexico State University,
Ohio State University, University of Pittsburgh, University of Portsmouth,
Princeton University, the United States Naval Observatory, and the
University of Washington.

IMAGE CAPTIONS:

[Image:
http://www.astronomy.ohio-state.edu/~dhw/SDSS08/sq372_orbit.jpg (85KB)]
The orbit of the newly discovered solar system object SQ372 (blue), in
comparison to the orbits of Neptune, Pluto, and Sedna (white, green, red).
The location of the Sun is marked by the yellow dot at the center. The inset
panel shows an expanded view, including the orbits of Uranus, Saturn, and
Jupiter inside the orbit of Neptune. Even on this expanded scale, the size
of Earth's orbit would be barely distinguishable from the central dot.
(Credit: N. Kaib)

[Animation:
http://www.astronomy.ohio-state.edu/~dhw/SDSS08/sq372_discovery_anim.gif
(2.3MB)]
Animation showing the detection of SQ372 by SDSS-II. Successive frames show
images from the SDSS-II supernova survey taken on October 21, 23, and 28,
2006. SQ372 changes position as it moves in its orbit, while the positions
of the stars, which are much more distant, stay fixed. (Credit: A. Becker
and SDSS)
Received on Tue 19 Aug 2008 08:19:50 PM PDT