Like a comet, it has a tail -- but unlike any other comet ever seen, the tail is composed of multiple trails of dust radiating from it like spokes in a wheel, the European Space Agency reported from its Paris headquarters Thursday.
European and U.S. astronomers studying the object say they don't have an adequate explanation for the mysterious appearance of what they have determined is an asteroid, because nothing like it has been seen before.
"We were literally dumbfounded when we saw it," lead investigator David Jewitt from UCLA said. "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."
One possible explanation, the scientists said, is an increase in the rotation rate of the asteroid to the point where its surface started flying apart, ejecting dust in episodic eruptions.
The tails could have been formed by radiation pressure from the sun smearing out the dust from those events into streamers, they said.
Rotational breakup may be a common phenomenon in the asteroid belt, Jewitt suggested, and may even be the main way in which small asteroids "die."
"In astronomy, where you find one, you eventually find a whole bunch more," he said. "This is just an amazing object to us, and almost certainly the first of many more to come."