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Astronomers find first asteroid with six comet-like tails

English.news.cn   2013-11-08 05:45:45            

WASHINGTON, Nov. 7 (Xinhua) -- U.S. and German astronomers said Thursday they have found for the first time an asteroid with six comet-like tails of dust in solar system's asteroid belt.

Unlike all other known asteroids, which appear simply as tiny points of light in space telescope, this asteroid, designated P/ 2013 P5, resembles a rotating lawn sprinkler, according to astronomers who are puzzled over the space rock's unusual appearance.

"We were literally dumbfounded when we saw it," lead investigator David Jewitt of the University of California at Los Angeles, said in a statement. "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."

P/2013 P5 has been ejecting dust periodically for at least five months. Astronomers said that it is possible the asteroid's rotation rate increased to the point where its surface started flying apart and the tails are unlikely to be 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 Aug. 27. The multiple tails were discovered when Hubble was used to take a more detailed image on Sept. 10.

When Hubble looked at the asteroid again on 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 researchers in Germany showed that the tails could have been formed by a series of impulsive dust- ejection events. They calculated that dust-ejection events occurred on April 15, July 18, July 24, Aug. 8, Aug. 26 and Sept. 4 and that radiation pressure from the Sun stretched the dust into streamers.

So far, only about 100 to 1,000 tons of dust, a small fraction of P/2013 P5's main mass, has been lost, the researchers said.

"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.

The findings were published in the U.S. journal The Astrophysical Journal Letters.

Editor: Mu Xuequan
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