NASA's Kepler Space Telescope Finds Hundreds Of New Exoplanets
by Clara Moskowitz - Scientific American/HuffPo
Posted: 02/26/2014 3:51 pm EST Updated: 02/26/2014 4:09 pm EST
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A huge new haul of planets has joined the tally of alien worlds discovered by NASA's Kepler space telescope, scientists announced today. All of the new planets are members of multiplanet systems—stars with more than one orbiting satellite. Researchers used a new method for weeding out false signals from among the candidate planets found by Kepler, allowing them to add hundreds of "validated" planets to the count of Kepler's finds. "We studied just over 1,200 systems, and from there we were able to validate 719 planets," says Jason Rowe of NASA Ames Research Center at Moffett Field, Calif., who led the research. "This is the biggest haul ever."
Kepler launched in 2009 and stopped taking data last year after two of its stabilizing reaction wheels failed. Its relatively short lifetime, however, has already offered up a wealth of discovery, including more than 3,500 planetary candidates as well as 246 worlds confirmed by follow-up observations. The new harvest brings its tally of true planets to over 1,000.
Kepler searches for planets by measuring stellar brightness dips caused when a planet passes in front of a star, briefly dimming the star's light. This technique, called the transiting method, is more than 90 percent accurate, but sometimes a nonplanet can fool the telescope. One of the most common reasons for a "false positive" is an eclipsing binary—a pair of orbiting stars that sometimes cross in front of one another from our perspective—lying along the same line of sight as the foreground star Kepler is studying. Eclipsing binaries dim when one star passes in front of the other, mimicking the dimming effect a planet would have.
Stars with a single planet can be hard to distinguish from eclipsing binaries. But multiplanet systems are far less likely to be frauds. "It happens, but it's unlikely that you have two eclipsing binaries in the background of the same star," says Francois Fressin of the Harvard–Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who was not involved in the study. "That simple fact tremendously increases the odds that they are bona fide planets." It is also possible to have an eclipsing binary and a star with a planet lying right on top of one another, albeit extremely unlikely. "Based on that argument we started to get into the statistics to see if we can quantify that and see how many we can pull out and say with very good confidence they are validated planets," Rowe says.
About 20 percent of the candidate planets Kepler finds...
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