NASA / JPL
An artist's conception shows an alien Earthlike planet.
I should have known it was too good to be true: Last month, it looked as if a world known as KOI 326.01 was the best hope among the Kepler mission's 1,235 candidates to be a second Earth. It was thought to be a bit smaller than Earth, and even better, it was located in a "habitable zone." That's the area of space surrounding a star where water could plausibly exist in liquid form. Those two characteristics — smaller than Earth, and in the habitable zone — put KOI 326.01 in a class by itself.
No more, unfortunately. A fact-checker at Discover magazine, Mara Grunbaum, called up the Kepler team for more information about the planet, presumably because it was going to be featured in a future issue. Members of the team, including San Jose State University's Natalie Batalha, double-checked their figures and determined that the planet candidate is actually somewhat warmer and much larger than originally estimated.
"The details of the planet need to be hammered out, but this certainly means that this is not an Earth-size planet in the habitable zone," Batalha is quoted as saying in a posting to the 80 Beats blog, part of Discover magazine's corner of the blogosphere. You can get the whole story behind KOI 326.01's demotion there.
That's the way it goes with these Kepler candidates: As more observations are gathered, checked and double-checked, the basic statistics for any particular candidate may need to be revised. And in some cases, the "candidate" may not exist at all. Instead, the supposed planetary detection may turn out to be merely the effect of two stars passing in front of each other. It will take months or years more to turn those candidates into confirmed planetary detections. But if you're hoping to hear about alien Earths, don't give up hope yet. Kepler's hunt continues.
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