Number of exoplanets doubles as NASA confirms 1,284 new worlds

U.S. space agency NASA said Tuesday its Kepler mission has verified the existence of nearly 1,300 new planets, almost doubling the number of known planets outside our solar system.

"Today, we are announcing the discovery of 1,284 new planets in the Kepler mission," lead author Timothy Morton, associate research scholar at the Princeton University, said at a NASA news teleconference. "This is the most exoplanets that have ever been announced at one time."

Ellen Stofan, NASA's chief scientist, said the finding "gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth."

Of the nearly 5,000 total planet candidates found to date, more than 3,200 now have been verified, and 2,325 of these were discovered by Kepler.

In the newly-validated batch of planets, nearly 550 could be rocky planets like Earth, based on their size, according to the study published in The Astrophysical Journal.

Nine of these orbit in their sun's habitable zone, which is the distance from a star where orbiting planets can have surface temperatures that allow liquid water to pool to potentially support life.

With the addition of these nine, 21 exoplanets now are known to be members of this exclusive group.

Since the discovery of the first planets outside the solar system more than two decades ago, researchers have resorted to a laborious, one-by-one process of verifying suspected planets.

The latest research, which employed a new statistical analysis method that can be applied to many planet candidates simultaneously, examined 4,302 potential planets from the Kepler mission's July 2015 planet candidate catalog.

For 1,284 of the candidates, the probability of being a planet is greater than 99 percent -- the minimum required to earn the status of "planet," the study said.

An additional 1,327 candidates are more likely than not to be actual planets, but they do not meet the 99 percent threshold and will require additional study.

The remaining 707 are more likely to be some other astrophysical phenomena.

Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. The spacecraft completed its prime mission in 2012 and began a new extended mission called K2 in 2014.

"Thanks to Kepler and the research community, we now know there could be more planets than stars," said Paul Hertz, NASA's astrophysics division director.

"This knowledge informs the future missions that are needed to take us ever-closer to finding out whether we are alone in the universe." Endit