First Earth-size planet that may hold water confirmed

Kepler-186f orbits an M dwarf star in the constellation Cygnus. More importantly, it's the first confirmed Earth-size, potentially habitable planet elsewhere in the universe.

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Eric Mack
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An artist's conception of Kepler-186f NASA/JPL-Caltech/T. Pyle

Just as real-estate prices in parts of North America have started to get expensive again, NASA says it has confirmed for the first time the existence of an Earth-like planet that may hold liquid water.

The planet is Kepler-186f and was discovered with NASA's Kepler telescope, originally launched in 2009 and recently crippled, but not before gathering enough data that researchers are still analyzing it and making discoveries like this.

Yes, this is kind of a big deal, as it's the "first validated Earth-size planet in the habitable zone of another star," as Elisa Quintana of the SETI Institute at NASA's Ames Research Center explained in a press conference Thursday.

"Some people call these habitable planets, which of course we have no idea if they are," San Francisco State University astronomer Stephen Kane, a member of the discovery team, said in a release. "We simply know that they are in the habitable zone, and that is the best place to start looking for habitable planets."

Kepler-186f is the fifth and outermost planet circling the M dwarf star Kepler-186 in the Milky Way, about 500 light years away in the constellation Cygnus.

A comparison of our solar system and that of M dwarf star Kepler-186. NASA Ames/SETI Institute/JPL-Caltech

"M dwarfs are the most numerous stars," said Quintana. "The first signs of other life in the galaxy may well come from planets orbiting an M dwarf."

According to NASA, the planet has a shorter year and might be a little chillier than Earth, depending on its atmosphere. It orbits its sun once every 130 days and only gets a third of the energy from its star that Earth gets from the sun -- that puts it near the outer edge of the habitable zone.

Besides being in the zone where liquid water is possible, "there's a very excellent chance that it does have a rocky surface like the Earth," Kane said.

While it will be a while before humans can start building condos on this Earth cousin, it won't be long before we start to have a better idea how common planets like Kepler-186f are in the universe.

"The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," Paul Hertz, NASA's Astrophysics Division director, said in a release. "Future NASA missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind's quest to find truly Earth-like worlds."

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