Alien Earths — 2 billion of them are out there

Roughly one out of every 37 to one out of every 70 sunlike stars in the sky might harbor an alien Earth, a new study reveals.

These findings hint that billions of Earthlike planets might exist in our galaxy, researchers added.

These new calculations are based on data from the Kepler space telescope, which in February wowed the globe by revealing more than 1,200 possible alien worlds, including 68 potentially Earth-size planets. The spacecraft does so by looking for the dimming that occurs when a world transits or moves in front of a star.

Scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., focused on roughly Earth-size planets within the habitable zones of their stars — that is, orbits where liquid water can exist on the surfaces of those worlds.

After the researchers analyzed the four months of data in this initial batch of readings from Kepler, they determined that 1.4 percent to 2.7 percent of all sunlike stars are expected to have Earthlike planets — ones that are between 0.8 and two times Earth's diameter and within the habitable zones of their stars.

"This means there are a lot of Earth analogs out there — 2 billion in the Milky Way galaxy," researcher Joseph Catanzarite, an astronomer at NASA's Jet Propulsion Laboratory, told Space.com. "With that large a number, there's a good chance life and maybe even intelligent life might exist on some of those planets. And that's just our galaxy alone — there are 50 billion other galaxies." ...

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