Kepler's Alien World Count Skyrockets

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The number of known planets beyond the solar system took a giant leap thanks to a new technique that verifies candidate planets found by NASA’s Kepler space telescope in batches rather than one-by-one.

What does it take to find a planet 63 light years from Earth? Devin Powell gets the answers from an astronomer who's done just that.
Antonio M. Rosario/Getty Images

The new method adds 715 planets to Kepler’s list of confirmed planets, which previously totaled 246, scientists said Wednesday.

Combined with other telescopes’ finds, the overall exoplanet headcount now reaches nearly 1,700.

"By moving ... to statistical studies in a 'big data' fashion, Kepler has showcased the diversity and types of planets present in our galaxy," astronomer Sara Seager, with the Massachusetts Institute of Technology, wrote in an email to Discovery News.

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The growing census reinforces previous findings that small planets are most common in the galaxy -- a boon for future missions aimed at finding planets in habitable zones around parent stars, Seager said.

It also shows that most planets, like those in our solar system, are part of multiple-planet systems. The 715 newly confirmed planets, for example, comprise 305 planetary systems.

The similarity to our own solar system ends there, however.

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The study confirms:

  • A binary star system with a total of three planets, two of which transit one star and one of which transits the second.
  • A star with seven planets all orbiting their parent star closer than Earth circles the sun.
  • A star with five confirmed planets, four of which orbit in less than 14 days and the fifth with an 87-day period. That system, newly named Kepler-169, also may have a sixth planet in a 30-day orbital period.

The planets circling Kepler-169 have plenty of elbowroom compared to Kepler-80, which has five candidate planets all circling their parent star in less than 10 days.

"We validate the four outer candidates (of Kepler-80) ... to be planets," astronomer Jack Lissauer, with NASA’s Ames Research Center in Moffett Field, Calif, wrote in paper to be published in The Astrophysical Journal.

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"The inner candidate has too short an orbital period for us to validate, but passes all of our other validation criteria," he wrote.

In a related paper in the same journal, astronomer Jason Rowe, also with NASA Ames, said the algorithm used to validate the 305 planetary systems has an accuracy rate of better than 99 percent.

“The vast majority of (the systems’ 715 planets) have not been previously identified as planets,” Rowe wrote.

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The studies were based on the first two years of Kepler data. The telescope, which was launched in 2009, operated for another two years before a positioning system failure in 2013 forced NASA to suspend operations.

The telescope worked by looking for slight dips in the amount of light coming from target stars caused by planets passing by, or transiting, relative to its line of sight.

NASA is reviewing proposals to use Kepler in an alternative mode for a mission known as K2.

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