Although some publications glossed over the uncertainty in announcing the first findings of the planet-hunting Kepler mission, researchers say the overall point remains true: Earth-like planets (meaning that they’re small and rocky, not that they have aliens writing blogs about science) are not only not rare–they’re the most common type of planet in our galaxy.
The first intimations of this news came out a few days ago in reports like the Daily Mail’s, which blared that NASA’s planet-hunting Kepler mission had found 140 new planets that were like the Earth in size, and that worlds like our own could dominate the Milky Way. That claim came after a presentation now available to view online by one of the scientists behind Kepler, Harvard’s Dimitar Sasselov.
But Sasselov and colleagues responded to Space.com, trying to quell some of the excitement–or at least hedge on the exact magnitude of the find:
“What Dimitar presented was ‘candidates,’” said David Koch, the mission’s deputy principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. “These have the apparent signature we are looking for, but then we must perform extensive follow-up observations to eliminate false positives, such as background eclipsing binaries. This requires substantial amounts of ground-based observing which is done primarily in the summer observing season” [Space.com]
The trouble arose after Kepler scientists kept a tight lip on their findings. Last month, they announced that their first round of research had found around 700 exoplanet candidates. (For comparison, there are fewer than 500 confirmed exoplanets now). But the team refused to discuss the details of about half of those planet candidates, and those are the ones most like the Earth. Given the scientific cred at stake, they wanted to analyze and publish papers before releasing data to the public.
Sasselov says he wasn’t giving out new information that wasn’t already available in papers published last month, but in the conference video he’s pretty direct about the cosmic importance of the findings, whether or not they’re merely candidates.
At 8:15 into his 18-minute talk, Sasselov showed a bar graph of planet size. Of the approximate 265 Kepler planets represented on the graph, about 140 were labeled “like Earth,” that is, having a radius smaller than twice Earth’s radius. “You can see here small planets dominate the picture,” said Sasselov. Until now, astronomers’ exoplanet finds had been more like gas giant Jupiter than rocky little Earth [ScienceNOW].
So, yes, the astronomers need to conduct a battery of tests and analyses to make sure the signals they’ve seen truly are planets. Only five of Kepler’s 700-plus haul of candidates are officially confirmed now.
But that doesn’t mean we shouldn’t be excited. Sasselov says they should be able confirm 60 of these Earth-like candidates at the very least. And even that would change our picture of the galaxy, and mean that many more planets like our own are out there.
“Even before we have confirmed the planets among these hundreds of candidates, we can see statistically that the smaller-sized planets will be more common than the large-sized (Jupiter- and Saturn-like ones) in the sample,” Sasselov explained [Space.com].
As his slide says during the presentation: “The galaxy is rich in small, Earth-like planets.”
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