"We were literally dumbfounded when we saw it," said David Jewitt, lead investigator from the University of California at Los Angeles. "Even more amazingly, 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."
So what is it? Needless to say, there are theories.
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The asteroid belt, that is located between the orbits of Mars and Jupiter, is home to a huge population of asteroids. Asteroids are known to be affected by the sun's radiation - like their cometary cousins, they heat up. But given enough time, asteroids can undergo what is known as the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect.
The uneven heating on an asteroid's surface can cause it to "spin up." In a nutshell, the YORP effect heats up the sun-facing side of an asteroid, but as the asteroid rotates, it radiates heat into space from the dark side. This heat radiation is carried away by infrared photons that themselves exert a tiny amount of momentum, or recoil, as they depart the asteroid. Over long periods (thousands to millions of years), this radiation acts to speed up an asteroid's spin.