Friday, November 8, 2013

Spinning Asteroid Ejects 6 Comet-Like Tails

Sept. 10, 2013 NASA Hubble Space Telescope images reveal a never-before-seen set of six comet-like tails radiating from an asteroid designated P/2013 P5. Image Credit: NASA, ESA, D.Jewitt/UCLA


CAPE CANAVERAL, Florida -- Using images taken by the Hubble Space Telescope, NASA astronomers have detected 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, 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."


The asteroid 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 on August 27 when  P/2013 P5 appeared as an unusually fuzzy-looking object.  The multiple tails were later discovered when Hubble was used to take a more detailed image on September 10.


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. 


Agarwal 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.


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.


Article Source: NASA / Space Telescope Science Institute, Baltimore, Md.