A team of astronomers from NASA and Princeton University has confirmed that 1,284 extrasolar objects by NASA’s planet-hunting Kepler spacecraft are indeed exoplanets.Reported in the Astrophysical Journal this week, it is the largest single finding of exoplanets to date and more than doubles the number of confirmed exoplanets discovered by NASA’s Kepler Space Telescope so far to 2,325.
“This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth,” said Dr. Ellen Stofan, chief scientist at NASA Headquarters in Washington.
The team’s discovery hinges on an automated technique that allows astronomers to efficiently analyze thousands of signals the planet-hunting Kepler spacecraft has identified to determine which are most likely to be caused by exoplanets and which are caused by non-planetary objects such as stars. This technique computes the chances that the signal is in fact caused by an exoplanet.
The researchers computed the reliability values for 7,056 signals identified in the Kepler’s July 2015 planet candidate catalog (known as the Q1-Q17 (DR24) Kepler Objects-of-Interest activity table), and verified the 1,284 planets with 99% certainty.
They also independently verified more than 700 additional planet signals that had already been confirmed as planets by other methods.
In addition, they identified 428 candidates as likely ‘false positives,’ or signals generated by something other than a planet.“Kepler, which ended data collection for its primary mission in 2013, operated by precisely measuring the brightness of many stars simultaneously,” said lead author Dr. Timothy Morton, from Princeton University.
“The satellite looked for stars that exhibited subtle and regular dimming, which indicates that an orbiting planet is passing in front of, or transiting, that star.”
“However, some scenarios can mimic the signature of a transiting planet, such as two stars that orbit each other, and provide a false positive signal. Distinguishing between true planets and false positives is one of the central challenges for any transiting planet survey.”In the newly-validated batch of planets, nearly 550 could be terrestrial planets like Earth, based on their size.
Nine of these – Kepler-560 b, Kepler-705 b, Kepler-1229 b, Kepler-1410 b, Kepler-1455 b, Kepler-1544 b, Kepler-1593 b, Kepler-1606 b and Kepler-1638 b — orbit in their Sun’s habitable zone.
With the addition of these nine, 21 exoplanets now are known to be members of this exclusive group.
“This work will help Kepler reach its full potential by yielding a deeper understanding of the number of stars that harbor potentially habitable, Earth-size planets – a number that’s needed to design future missions to search for habitable environments and living worlds,” said co-author Dr. Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center.
