Millions of Earths? Talk causes a stir


Alan Boyle writes: A leader of the Kepler planet-hunting team has created a slow-moving scientific stir by telling an audience at a high-tech conference that our galaxy could harbor 100 million Earths, based on the space mission’s raw data. The resulting buzz focuses not only on the findings, but also on the means by which they came to light.

The conclusions drawn by Harvard astronomer Dimitar Sasselov totally make sense, based on the composition of our own solar system. If we look at the eight dominant planets, four of them are Earth-scale, two are Neptune-scale, and the other two are big gas giants. (And then there are hundreds or thousands of smaller worlds like Pluto.)

During his July 16 talk at the TEDGlobal conference at Oxford, Sasselov observed that the preliminary results from Kepler were following that pattern. So far, planetary candidates “like Earth” – those that are no more than twice as wide as our own planet – make up the largest category in Kepler’s database, according to a chart Sasselov used to illustrate his talk. The proportion is significantly more than that for Neptune-sized, Saturn-sized or Jupiter-sized candidates. (These observations came just after the eight-minute mark in the video embedded above.)

“The statistical result is that planets like our own Earth are out there,” Sasselov, a co-investigator for the $600 million Kepler mission, observed. “Our Milky Way galaxy is rich in this kind of planet.”

If you extrapolate that kind of distribution to the entire Milky Way galaxy, there might be 100 million alien Earths out there, Sasselov said.


Once Sasselov’s comments started making their way across the interwebs, NASA began facing questions over whether significant findings had slipped out of the Kepler team’s net.

Some news outlets, such as the Daily Mail, fixed upon the suggestion in Sasselov’s chart that 140 Earthlike candidates had been found, as well as his comment that Earthlike planets “with water and with rocks” were of particular interest. The buzz over Sasselov’s remarks picked up last week when the TED website posted a video of his presentation.

New news, or new spin?
Responding to the buzz, NASA stressed that the Kepler team has confirmed detection of only five planets, not the 140 mentioned in the news reports. Sasselov, meanwhile, told that he was “simply repeating what was already announced” last month by the full science team.



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