Scientists with NASA's Kepler mission announced Wednesday that the number of verified planets beyond our solar system (also called exoplanets) has increased by 715. These newly confirmed exoplanets orbit 310 stars,many are in multi-planet systems much like our solar system. Almost 95 percent of these worlds are smaller than Neptune, which is almost four times the size of the Earth. Four of the newly announced planets are less than 2.5 times lager than the Earth and orbit in their sun's habitable zone where the surface temperature of the planet may be suitable for liquid water.
"The Kepler team continues to amaze and excite us with their planet hunting results," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "That these new planets and solar systems look somewhat like our own, portends a great future when we have the James Webb Space Telescope in space to characterize the new worlds.”
The treasure trove of planets were confirmed using a technique called verification by multiplicity. Kepler has observed 150,00 stars and has found a few thousand of those to have planet candidates. If the potential candidates were distributed randomly amongst the stars Kepler observes, very few would have more than one planet candidate. Kepler, however, has observed hundreds of stars with multiple planet candidates. The 715 new planets were confirmed through careful study of this sample.
"Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates --but they were only candidate worlds," said 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."
All of the newly confirmed planets came from the first half of Kepler's four-year primary mission. Many more could be announced as more recent data is analyzed using the new technique. In 2017 NASA plans to launch its next planet hunter, the Transiting Exoplanet Survey Satellite (TESS).
The Kepler team is continuing to test the spacecraft for a new mission phase that they refer to as K2 which will allow Kepler to continue its search for exoplanets despite having lost two reaction wheels which help point its telescope and hold it steady. In a recent update, mission manager Roger Hunter of NASA's Ames Research Center reported that one of the 21 science detectors that Kepler uses to search for transiting planets had failed.Another detector had died early in the mission, nearly four years ago. Hunter said that the failure should not impact the potential K2 mission because the remaining 19 modules still allow for a very large view of the sky and the area observed by the failed detector could be assigned to other units. In early March, Kepler will begin a data gathering campaign which will be an engineering dress-rehearsal for the K2 mission.