Comet or asteroid? Scientists ID interstellar visitor
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CAPE CANAVERAL, Fla. (AP) - Our first known visitor from another star system has now been identified as a comet.
A European-led team makes the case in Wednesday's edition of the journal Nature.
Telescopes first spotted the mysterious cigar-shaped object last October as it zipped through the inner solar system. Since then, astronomers have flip-flopped between comet and asteroid.
Neither a coma nor tail was spotted, hallmarks of an icy comet. But Italian astronomer Marco Micheli (Mee-KAY-lee) and his team report that the object's path and acceleration are best explained not just by gravity, but also gases shedding from a comet.
It's long gone, as are the chances of knowing conclusively what it was.