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March 5, 2014

NASA Confirms 715 New Exoplanets from Kepler Data Haul

Tiffany Trader

Astronomy is one of the more data-intensive sciences, as we have explored before. A new study from NASA highlights the importance of techniques that can keep pace with all that data.


Last week Kepler team astronomers announced that 715 exoplanet candidates found by NASA’s now-disabled Kepler probe have been confirmed as planets. It’s the biggest haul ever, according to project co-lead Jason Rowe of the SETI Institute in Mountain View, California, and it reveals many multi-planet solar systems much like our own.

The jackpot nearly quadruples the number of validated alien worlds found by Kepler, and boosts the total number of known planets beyond the Earth’s solar system from 1,035 to 1,750, according to a Nature article. Researchers used a new method for identifying true exoplanets from a cache of more than 1,200 candidates discovered by Kepler. Where confirmation used to be a laborious planet-by-planet process, researchers have developed a more streamlined approach, based on statistics.

NASA’s Kepler began its mission to find planets outside Earth’s solar system in 2009 and stopped taking data last year after experiencing a mechanical failure. But even in its shortened life span, Kepler was prolific, responsible for identifying more than 3,600 planetary candidates. Kepler located candidate planets by observing stars for changes in brightness. A dip in stellar brightness usually indicates a planet has crossed in front of its parent star. The so-called transiting method is more than 90 percent accurate, but sometimes a non-planet can cause a false reading.

The primary source of false positives among the Kepler candidates are eclipsing binary stars. When one star crosses the path of another in the line of sight of the telescope, it mimics the dimming effect that a real planet would have. Distinguishing the light signatures of actual planets from the various kinds of false positives is both compute- and data-intensive, leading researchers to seek an alternative approach.

Previous work showed that candidate planets that orbit a star in the company of one or more other planets have only a 0.2 percent chance of being false planets, compared with a 10 percent rate for candidate planets orbiting solo. Using a technique called verification by multiplicity, which relies on probability and statistics, the research team was able to weed out false positives and validate 715 new exoplanets with a confidence level of greater than 99 percent, bringing Kepler’s total haul to 961.

Jason Rowe and his colleague Jack Lissauer, planetary scientist at NASA’s Ames Research Center in Moffett Field, Calif., present their analyses in two papers, soon to be published in the Astrophysical Journal.

“Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates – but they were only candidate worlds,” reports Lissauer. “We’ve now developed a process to verify multiple planet candidates in bulk to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds.”

“We can tell that most of the multiple-planet candidates are good, with only a handful of problem cases,” Rowe adds.

The treasure trove of planetary data provides us with an enhanced understanding of the cosmos. Among the 150,000 stars that Kepler monitored, multiple-planet systems are relatively common. The 715 newly verified planets were grouped around 305 stars. The planetary systems have orbits that are similar to terrestrial planets, flat and circular, more like pancakes than the classic atom shape. Four of the newly discovered planets were about double the size of Earth and were in the habitable zone of their stars, the region that, like Earth, has surface temperatures suitable for life-sustaining liquid water.

It’s a fascinating glimpse into scaled-down versions of our inner solar system, allowing us to see hints of ourselves, says Rowe.