[meteorite-list] First Detailed Pictures of Binary Asteroid Reveal Bizarre System

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Oct 13 12:55:53 2006
Message-ID: <200610131655.JAA28110_at_zagami.jpl.nasa.gov>

http://www.ns.umich.edu/htdocs/releases/story.php?id=986

First detailed pictures of asteroid reveal bizarre system
University of Michigan
October 12, 2006

ANN ARBOR, Mich. - The first detailed images of a binary asteroid system
reveal a bizarre world where the highest points on the surface are
actually the lowest, and the two asteroids dance in each other's
gravitational pull.

A binary asteroid is a system where two asteroids orbit around one
another, like a mini Earth-moon system, said Daniel Scheeres, University
of Michigan associate professor of aerospace engineering. The new
results are scheduled to appear Oct. 12 in the journal Science in a pair
of papers by Scheeres and Dr. Steven Ostro of the NASA/Caltech Jet
Propulsion Laboratory.

The radar images of asteroid KW4 (the official full designation is 66391
1999 KW4) were obtained in May 2001, when the asteroid passed 4.8
million kilometers from Earth. Previously, KW4 was classified as a
potentially hazardous asteroid (PHA) because of the proximity of the
asteroid's orbit to Earth's orbit. The new observations show that there
is no chance of KW4 hitting Earth within at least the next 1,000 years,
Scheeres said.

"The KW4 results have profound consequences for ideas about mitigation
of the asteroid collision hazard," Scheeres said.

The observations show that the larger object is spinning in its orbit so
fast that it has been flattened into a kind of flying saucer shape, said
Scheeres. Because of this, the mountainous region along the center of
the asteroid actually forms the lowest part on the asteroid. In fact the
asteroid is spinning so fast that the equatorial ridge is very close to
lifting off the surface and spinning into space, he said.

Another interesting finding is that the two bodies in the asteroid
system are orbiting so closely that they are caught in each other's
gravitational pull.

"They are so close together that when one rotates it affects the other's
movements," Scheeres said.

Based on the observations, the KW4 binary asteroid appears to have
formed either from tidal disruption during a close pass by the Earth or
from sunlight shining on it, so that it spins so fast that it eventually
broke into two pieces. The odd shapes of asteroids cause them to
sometimes spin faster and faster when illuminated by the sun, acting a
bit like a solar sail, Scheeres said. \This is called the YORP effect.

The recent findings also confirm that the asteroids are only floating
piles of rubble held together by gravity and not a solid mass.

The University of Michigan College of Engineering is ranked among the
top engineering schools in the country. Michigan Engineering boasts one
of the largest engineering research budgets of any public university, at
more than $130 million. Michigan Engineering has 11 departments and two
NSF Engineering Research Centers. Within those departments and centers,
there is a special emphasis on research in three emerging areas:
nanotechnology and integrated microsystems; cellular and molecular
biotechnology; and information technology. Michigan Engineering is
seeking to raise $110 million for capital building projects and program
support in these areas to further research discovery. Michigan
Engineering's goal is to advance academic scholarship and market
cutting-edge research to improve public health and well-being. For more
information, visit the Michigan Engineering home page:
http://www.engin.umich.edu
 

Related Links:

For more information on Scheeres
<http://www.personal.engin.umich.edu/~scheeres/>

U-M aerospace engineering <http://aerospace.engin.umich.edu/index.html>

Contact: Laura Bailey <mailto:baileylm_at_umich.edu>
Phone: (734) 647-1848
Received on Fri 13 Oct 2006 12:55:50 PM PDT