This artist rendering provided by NASA/JPL-Caltech/T. Pyle, taken in 2015, depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of a star that is similar to our sun.
NASA has discovered 10 brand-new planets which it believes are Earth-like, within the habitable zone and so could theoretically support alien life.
The Kepler spacecraft continues to make observations in new patches of sky in its extended mission, searching for planets and studying a variety of interesting astronomical objects, from distant star clusters to objects such as the TRAPPIST-1 system of seven Earth-size planets, closer to home.
Kepler has spotted more than 4,000 planet candidates and confirmed more than half of those. Earth-sized planets are of particular interest because they can teach us about how our own planet formed, and because there's a small chance they could harbor life.
The telescope was viewing the Cygnus constellation in our Milky Way galaxy.
In total, Kepler has now identified 4,034 candidate planets, with 2,335 of those confirmed to be planets orbiting a star outside Earth's solar system, otherwise known as extrasolar or exoplanets.
"They say not to count our chickens before they're hatched, but that's exactly what these results allow us to do based on probabilities that each egg (candidate) will hatch into a chick (bona fide planet)". When scientists see this happen, they then study each signal to confirm that it's coming from a planet passing in front of the star and not some other anomaly. Like other missions that have outlived their expected lifespan, Kepler broadened its search in 2014 to include other parts of our galaxy and has been taking in data ever since.
The closest of those identified planets is just about four light years away, NASA researchers said during Monday's press conference. A dozen of the planets that seem to be in the potentially habitable zone circle Earth-like stars, not cooler red dwarfs.
These planets are usually 1.6 times the size of Earth, with rocky terrain. Astronomers were at a loss to explain how such planets formed and whether there was a continuum between rocky terrestrial "super-Earths" and gassy "mini-Neptunes". "KOI" stands for "Kepler object of interest".
This isn't the first time the space agency has identified potentially inhabitable exoplanets. "That's great", said Courtney Dressing, a NASA Sagan Fellow at the California Institute of Technology. "I, for one, am ecstatic". His work can be found here.
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