100 new alien planets discovered by NASA mission

NASA's revamped planet-hunting Kepler spacecraft has discovered more than 100 confirmed planets orbiting other stars. Kepler, which recently got crippled by a mechanical malfunction, discovered the alien planets during its second-chance K2 mission.

The spacecraft finds planets by the "transit method," noting the tiny brightness dips caused when a planet crosses its host star's face from Kepler's perspective. This technique requires extremely precise pointing, an ability Kepler lost in May 2013 when the second of the observatory's four orientation-maintaining reaction wheels failed.

However, the Kepler team quickly figured out a way to keep the telescope stable, using solar radiation pressure as a sort of third wheel. That meant the spacecraft could eye different patches of the sky for around 80 days at a time to search for planets and other cosmic bodies and phenomena, 'Space.com' reported.

The first five K2 campaigns, which each looked at a different part of the sky, "have produced over 100 validated planets," Ian Crossfield, an astronomer at the University of Arizona, said. "This is a validation of the whole K2 programme's ability to find large numbers of true, bona fide planets," said Crossfield. He said that Kepler observed more than 60,000 stars and found 7,000 transit-like signals during the first five 80-day observation campaigns.

A validation process whittled some of these signals down to planet candidates, and then finally to validated planets, each of which has just a 1 per cent chance of being a false positive, Crossfield added. Kepler was launched in March 2009 tasked with determining how commonly Earth-like planets occur throughout the Milky Way galaxy. The mission has been incredibly successful, finding more than 1,000 alien worlds to date, more than half of all exoplanets ever discovered.