November 7, 2013
Six-Tailed Asteroid Caught By NASA’s Hubble Space Telescope
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers using the NASA Hubble Space Telescope have witnessed an asteroid with six comet-like tails of dust.
"We were literally dumbfounded when we saw it," said lead investigator David Jewitt of the University of California at Los Angeles. "Even more amazing, 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, and astronomers believe it is possible the space rock’s rotation rate increased to the point where its surface started breaking apart. The scientists 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.
Computer modeling has shown that the tails could have been formed by a series of impulsive dust-ejection events. Jessica Agarwal of the Max Planck Institute for Solar System Research in Lindau, Germany calculated that dust-ejection events occurred on April 15, July 18, July 24, Aug. 8, Aug. 26 and Sept. 4. Radiation pressure from the sun helped to stretch the dust into the lawn-sprinkler-like streamers.
Jewitt, lead author of the paper published in The Astrophysical Journal Letters, said the spin rate could have increased so much so that the asteroid’s weak gravity could no longer hold it together. Assuming this was the case, the dust could have slid towards the asteroid’s equator, shattered and fell off, and then drifted off into space to make the tails.
Astronomers calculate that about 100 to 1,000 tons of dust have been lost so far, which is just a fraction of the asteroid’s main mass. P/2013 P5 measures 1,400 feet wide and its nucleus is thousands of times more massive than the observed amount of ejected dust.
The researchers plan to continue observing the asteroid to see whether the dust leaves the asteroid in the equatorial plane. If this ends up being the case then it would be strong evidence for a rotational break up.
Jewitt believes that if this is in fact a rotational break up, then it could mean this is a common occurrence in the asteroid belt. He even said it could be evidence that this is the main way small asteroids die.
"In astronomy, where you find one, you eventually find a whole bunch more," Jewitt said in a statement. "This is just an amazing object to us, and almost certainly the first of many more to come."