artist's impression of exoplanets orbiting a star
June 20, 2017

NASA finds 10 more habitable, Earth-like exoplanets

NASA's planet-hunting Kepler Space Telescope mission has resulted in the discovery of more than 200 new candidates since the last time data was released by the US space agency, including 10 nearly-Earth sized, potentially habitable new worlds, various media outlets have reported.

During a briefing held on Monday, Kepler scientists revealed that the latest round of discoveries brings the overall number of candidate planets discovered by the telescope to 4,034, according to Of those, 2,335 have been confirmed by follow-up observations.

In addition, the 10 new, nearly-Earth-sized candidate planets found to be orbiting in their star’s habitable zones (meaning that they were the correct distance for liquid water to pool and persist on the surface of a rocky planet) boost the number of such worlds discovered thus far to 50. Of those discoveries, 30 have been confirmed to date, the agency said during its briefing.

In a statement, NASA called Monday’s announcement “the most comprehensive and detailed catalog release of candidate exoplanets... from Kepler’s first four years of data. It’s also the final catalog from the spacecraft’s view of the patch of sky in the Cygnus constellation.”

Transit method used to discover 4,000 potential new worlds

Launched in 2009, Kepler had been monitoring the roughly 200,000 stars in Cygnus, a northern constellation resting on the plane of the Milky Way, during the initial phase of its mission, the Washington Post noted. Its goal was to collect demographic data about our galaxy: for instance, to learn how many stars are similar to our sun, or how many planets could support biological life.

Kepler, which NASA said has discovered more than 80% of all known confirmed exoplanets and candidate planets identified to date, uses what it known as the transit method, which means that it tracks stars over extended periods of time looking for brief periods of dimming. Those periods of dimming, they explained, indicate a potential planet crossing between the star and Earth.

According to, the telescope detected about 34,000 signals while studying the Cygnus constellation, indicating a combination of transiting planets and background noise that may have come from either the star being studied or the instrument itself. Additional analysis whittled that figure down to approximately 4,000 candidates, including the 50 Earth-like habitable planets.

Analysis also uncovers ‘new division’ in exoplanet ‘family tree’

Furthermore, the Kepler scientists revealed that there was a surprising dichotomy when it came to smaller worlds: rather than coming in a variety of different types, they primarily fell into one of just two different categories – small, Earth-like worlds or gaseous Neptune-like planets.

“This is a major new division in the family tree of exoplanets, somewhat analogous to the discovery that mammals and lizards are separate branches on the tree of life,” Benjamin Fulton, who is a researcher at the University of Hawaii in Manoa and California Institute of Technology (Caltech), explained at Monday’s briefing, according to

Fulton and his colleagues used the Keck Observatory in Hawaii to determine the size of 1,300 stars measured by Kepler, then used that data to calculate the size of the planet candidates the telescope had detected. While they anticipated finding a range of worlds between one and four times that of Earth, they would that most were either rocky planets up to 1.75 times as large as our planer, or dense gas worlds (mini-Neptunes) 2.0 to 3.5 the size of the Earth.

“It's amazing the things that Kepler has found,” said Kepler scientist Susan Thompson of the SETI Institute in California.  “It has shown us these terrestrial worlds, and we still have all this work to do to really understand how common Earths are in the galaxy. I'm really excited to see what people are going to do with this catalog.”


Image credit: NASA JPL/Caltech