Back in August, astronomers using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey telescope in Hawaii discovered an unusually fuzzy-looking object dubbed P/2013 P5. Later, on September 10, when the Hubble Space Telescope took a look, it revealed that the asteroid had sprouted six tails!
When Hubble returned less than two weeks later to re-photograph P/2013 P5, the entire tail structure had swung over to the other side of the asteroid. What’s going on here? Scientists think the asteroid’s rotation rate has increased to the point where it’s flinging dust from its surface into space. The pressure of sunlight pushes the dust away, forming a tail(s) just like a comet. As P/2013 P5 rotates and periodically releases dust, the tails twist about in different orientations.
Unlike asteroids, comets are composed of dust-impregnated ice; when they’re heated by the sun, some of the ice vaporizes, liberating dust that’s then pushed back into a tail by the pressure of the solar wind. P/2013 P5 looks superficially similar to a comet but it’s smack dab in the asteroid belt and studies of the tails indicate they were released in a series of “dust-ejections” on April 15, July 18, July 24, Aug. 8, Aug. 26 and Sept. 4.
“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 measures about 1,400 feet (427 meters) across and shines at a very dim magnitude 20, well beyond the limits of visual observing in amateur telescopes. It’s believed radiation (light and heat) pressure from the sun spun up P/2013 P5 causing it to lose dust from its equator into space – a first step in the potential breakup of the asteroid.
As of now, it’s lost only about 1,000 tons of dust, a small fraction of its mass. Astronomers plan to study the asteroid closely to see if it disintegrates. P/2013 P5’s dusty fits may shed light on how asteroids break down into ever smaller pieces, some of which are perturbed by Jupiter, end up in orbits that cross that of Earth and eventually land on our planet as meteorites.