NASA has announced that the team behind the planet-hunting Kepler Telescope has discovered 10 new Earth-like, or “terrestrial,” planets amidst 219 planet candidates. A planet candidate means that Kepler has returned data that suggest that there might be a planet orbiting another star, but scientists wish to confirm that a planet actually exists by observing the host star of a possible planet candidate until the candidate has had a chance to transit that star at least three times.
So far, Kepler has discovered 4,034 planet candidates, of which 2,335 have been confirmed as actual exoplanets. 30 of the confirmed planets are about the same size of Earth or a little larger, and reside in their host star’s habitable zone. Scientists have indicated that they are still reviewing the massive amounts of data that Kepler returns and there may be more planet candidates in that data than they have noticed so far.
If life resides elsewhere in the universe, that life is most likely to exist on rocky planets like the highly promising exoplanet labeled 7711, which is a rocky planet that is 1.3 times the size of Earth and orbits within the habitable zone of a star similar to our own. Future telescopes like the James Webb Telescope will be capable of helping us study these worlds, including learning more about their chemical makeup.
Scientists are also interested in the fact that they haven’t found any planets with radii between 1.5 and 2 times Earth’s radius. Rocky planets like Earth tend to be less than 1.5 times Earth’s radius and gaseous “mini-Neptunes” are never less than 2 times Earth’s radius.
Benjamin Fulton from the University of Hawaii in Manoa said of the division between the sizes of rocky planets and gaseous planets, “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”
With this discovery of 10 possible Earth-like planets, Kepler has completed its primary mission and will now move on to a secondary mission labeled K2. While this mission will make it less likely that Kepler will actually confirm planets, it can still provide clues about where planets might reside and which types of planets might be scattered throughout the cosmos so that scientists can refine their search parameters using future hardware like the James Webb Telescope and the upcoming Transiting Exoplanet Survey Satellite (TESS), which will monitor more than 200,000 stars in the solar neighborhood for signs of possible planets.