[meteorite-list] NASA's Hubble Sees Asteroid Spouting Six Comet-Like Tails

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 7 Nov 2013 11:00:06 -0800 (PST)
Message-ID: <201311071900.rA7J06aO005327_at_zagami.jpl.nasa.gov>

November 7, 2013

J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington at nasa.gov

Donna Weaver/Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver at stsci.edu / villard at stsci.edu
     
RELEASE 13-321
     
NASA's Hubble Sees Asteroid Spouting Six Comet-Like Tails

Astronomers viewing our solar system's asteroid belt with NASA's Hubble Space
Telescope have seen for the first time an asteroid with six comet-like tails
of dust radiating from it like spokes on a wheel.

Unlike all other known asteroids, which appear simply as tiny points of
light, this asteroid, designated P/2013 P5, resembles a rotating lawn
sprinkler. Astronomers are puzzled over the asteroid's unusual appearance.

"We were literally dumbfounded when we saw it," said lead investigator David
Jewitt of the University of California at Los Angeles. "Even more amazing,
its tail structures change dramatically in just 13 days as it belches out
dust. That also caught us by surprise. It's hard to believe we???re looking
at an asteroid."

Jewitt leads a team whose research paper appears online in the Nov. 7 issue
of the Astrophysical Journal Letters.

P/2013 P5 has been ejecting dust periodically for at least five months.
Astronomers believe it is possible the asteroid's rotation rate increased to
the point where its surface started flying apart. They do not believe the
tails are the result of an impact with another asteroid because they have not
seen a large quantity of dust blasted into space all at once.

Scientists using the Pan-STARRS survey telescope in Hawaii announced their
discovery of the asteroid Aug. 27. P/2013 P5 appeared as an unusually
fuzzy-looking object. The multiple tails were discovered when Hubble was used
to take a more detailed image Sept. 10.

When Hubble looked at the asteroid again Sept. 23, its appearance had totally
changed. It looked as if the entire structure had swung around.

"We were completely knocked out," Jewitt said.

Careful modeling by team member Jessica Agarwal of the Max Planck Institute
for Solar System Research in Lindau, Germany, showed that the tails could
have been formed by a series of impulsive dust-ejection events. She
calculated that dust-ejection events occurred April 15, July 18, July 24,
Aug. 8, Aug. 26 and Sept. 4.?? Radiation pressure from the sun stretched the
dust into streamers.

Radiation pressure could have spun P/2013 P5 up. Jewitt said the spin rate
could have increased enough that the asteroid's weak gravity no longer could
hold it together. If that happened, dust could slide toward the asteroid's
equator, shatter and fall off, and drift into space to make a tail. So far,
only about 100 to 1,000 tons of dust, a small fraction of the P/2013 P5's
main mass, has been lost. The asteroid's nucleus, which measures 1,400 feet
wide, is thousands of times more massive than the observed amount of ejected
dust.

Astronomers will continue observing P/2013 P5 to see whether the dust leaves
the asteroid in the equatorial plane. If it does, this would be strong
evidence for a rotational breakup. Astronomers will also try to measure the
asteroid's true spin rate.

Jewitt's interpretation implies that rotational breakup must be a common
phenomenon in the asteroid belt; it may even be the main way small asteroids
die.

"In astronomy, where you find one, you eventually find a whole bunch more,"
Jewitt said. "This is just an amazing object to us, and almost certainly the
first of many more to come."

Jewitt said it appears P/2013 P5 is a fragment of a larger asteroid that
broke apart in a collision roughly 200 million years ago. There are many
collision fragments in orbits similar to P/2013 P5's. Meteorites from these
bodies show evidence of having been heated to as much as 1,500 degrees
Fahrenheit. This means the asteroid likely is composed of metamorphic rocks
and does not hold any ice as a comet does.

For images and more information about P/2013 P5, visit:

http://hubblesite.org/news/2013/52

For more information about NASA's Hubble Space Telescope, visit:

http://www.nasa.gov/hubble

-end-
Received on Thu 07 Nov 2013 02:00:06 PM PST


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