If you thought tails were just for comets and cats, this asteroid is about to prove you wrong.
On August 27 astronomers spotted an unusually fuzzy looking object in survey images taken with the Pan-STARRS telescope in Hawaii. The multiple tails were discovered in Hubble images taken on September 10, 2013. When Hubble returned to the asteroid two weeks later, its appearance had totally changed — it looked as if the entire structure had swung around!
While this object is on an asteroid-like orbit, it looks like a comet, and is sending out tails of dust into space. Because nothing like this has ever been seen before, astronomers are scratching their heads to find an adequate explanation for its mysterious appearance.
One interpretation is that the asteroid’s rotation rate has increased to the point where dust is falling off the surface and escaping into space, where it is swept out into tails by the pressure of sunlight. According to this theory, the asteroid’s spin has been accelerated by the gentle push of sunlight. Based on an analysis of the tail structure, the object has ejected dust for at least five months.
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. Radiation pressure from the Sun smears out the dust into streamers.
“Given our observations and modeling, we infer that P/2013 P5 might be losing dust as it rotates at high speed,” says Agarwal. “The Sun then drags this dust into the distinct tails we’re seeing.”
The asteroid could possibly have been spun up to a high speed as pressure from the Sun’s light exerted a torque on the body. If the asteroid’s spin rate became fast enough, suggests lead investigator David Jewitt of UCLA, the asteroid’s weak gravity would no longer be able to hold it together. Dust might avalanche down towards the equator, and maybe shatter and fall off, eventually drifting into space to make a tail. So far, only a small fraction of the main mass, perhaps 100 to 1000 tons of dust, has been lost. The asteroid is thousands of times more massive, with a radius of up to 240 meters.
“In astronomy, where you find one, you eventually find a whole bunch more.”
– David Jewitt, UCLA
Jewitt’s interpretation implies that rotational breakup may be a common phenomenon in the asteroid belt; it may even be the main way in which 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.”
Space… it’s like a box of chocolates, you never know what you’re gonna get.
Source: Hubble news release