Scientists find 20 more potentially habitable exoplanets from Kepler data

Discoveries bring number of known habitable Earth-like worlds to 50.
By Laurel Kornfeld | Nov 07, 2017
Scientists studying data returned by NASA's Kepler space telescope have found 20 new potentially habitable exoplanets.

All were discovered in data from Kepler's initial four-year exoplanet search between 2009 and 2013. Because of problems that developed in 2013 with two of its reaction wheels, the telescope could no longer maintain precise focus on target stars, ending the initial mission.

By the time the problem developed, the telescope had already observed more than 150,000 stars, meaning there is a huge amount of data for scientists to process.

The telescope was re-purposed in 2014 to function without reaction wheels, using radiation pressure from the Sun to keep it stable.

Using a tool called a Robovetter, an international team of scientists perused Kepler data in an effort to identify planets most likely to support life.

A complete catalog of the data collected by Kepler in its initial mission lists 8,054 "objects of interest," of which 4,034 are planet candidates.

Confirmation requires three recorded transits of a planet in front of its star. Because of Kepler's malfunctioning reaction wheels, only one or two transits were observed for some of the candidate planets.

The 20 worlds selected from this group as most likely to have conditions favorable to supporting life have orbital periods ranging from six hours to 632 Earth days.

Although they acknowledge further observations with both ground- and space-based telescopes are necessary, members of the science team are 70 to 80 percent confident that these worlds are planets and that they are habitable.

If the scientists are correct, that will bring the total number of potentially habitable, roughly Earth-sized planets, to 50.

One particular world stands out as Earth-like. KOI-7923.01 is approximately 97 percent the size of Earth and orbits its star every 395 days.

Because the star is slightly cooler than the Sun and the planet somewhat more distant than Earth is from the Sun, KOI-7923.01 is likely a cooler world with a frozen tundra but still capable of supporting life.

"If you had to choose one to send a spacecraft to, it's not a bad option," said Kepler team lead Jeff Coughlin, who is lead author of a paper on the findings scheduled for publication in the journal Earth and Planetary Astrophysics.

Because these 20 worlds are the ones most likely to support life, they will be given top priority for future observations.

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