Skywatchers have noticed something "bizarre" in the data from the planet-hunting Kepler telescope. Located 1,480 light-years away, a star named KIC 8462852 has something big circling around it, and it's not a planet.

Usually when a planet passes in front of a star, it dims the star's light for a few hours or days, then disappears and returns again after completing its yearly revolution around its sun. But this particular star's light has dimmed for up to 80 days at a time, and at irregular intervals. That's no planet.

Nor is it likely to be a clot of dust and rocks. Those sorts of debris disks are only known to occur around young stars, and this star is not a young 'un. Plus, debris usually gives off extra infrared radiation, which is not the case here. The data has been validated by the Kepler team, and the telescope was functioning fine when it collected the data.

That leaves just a few possible explanations. One is that perhaps a wandering star pulled foreign comets into orbit around the star. Such a phenomenon is probably rare. "It's a bit of a stretch," says Andrew Siemion, a scientist with Berkeley's SETI center. The mysterious object(s) are blocking up to 20 percent of the star's light, which is much, much more than even a Jupiter-sized planet would block.

Siemion and two other astronomers have suggested an alternate explanation that may be even less likely than comets, but still very intriguing: Perhaps the star's light is being blocked by huge pieces of alien architecture.

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