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Earth-like planets next door? Prospect could point to 9.6 billion more

A new study calculates that the nearest Earth-like planet may be only 13 light-years away – and argues there may be more habitable planets out there than we thought. 

By Staff writer / February 6, 2013

This artist's conception provided by the Harvard-Smithsonian Center for Astrophysics shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. Earth-like worlds may be closer and more plentiful than anyone imagined. Astronomers reported Wednesday.

David A. Aguilar/Harvard-Smithsonian Center for Astrophysics/AP



The nearest potentially habitable, Earth-like planet may be a scant 13 light-years away – close enough that any hypothetical, tech-savvy inhabitants there could start enjoying the second season of "The Sopranos" right about now.

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Indeed, there should be at least three Earth-size planets orbiting in the habitable zones of stars within 33 light-years of Earth, according to a new analysis of data from NASA's Kepler mission.

That would put detailed studies of such planets – and the hunt for signatures of life on them – well within the reach of a new generation of space telescopes, including the James Webb Space Telescope, currently slated for launch in October 2018.

Launched in March 2009, Kepler is monitoring some 158,000 stars across the constellations Cygnus and Lyra for signs of planets. The ultimate goal is to detect Earth-like planets orbiting sun-like stars.

Along the way, however, the mission has also been gathering statistics on the size and type of planets orbiting different stars. Based on those data, the team conducting the new study concludes that some 6 percent of the smallest, coolest types of stars in the galaxy – red dwarfs – host planets with a mass similar to Earth's that are also in habitable zones. 

Up to 80 percent of the stars in the galaxy are thought to be red dwarfs. If 6 percent have an Earth-like planet, that means the galaxy could host between 9.6 billion and 19.2 billion potentially-habitable Earths around these stars alone. 

The results reinforce a growing recognition that our solar system, with its larger, hotter star, "is quite rare," says John Johnson, an astronomer at the California Institute of Technology in Pasadena who studies extrasolar planets. "It's quite remarkable that the vast majority of habitable planets throughout the galaxy are likely around these red dwarfs." 

The results also "highlight just how quickly the field of extrasolar planets is blooming," he adds.

In 2000, astronomers had only detected 33 planets, all gas giants the size of Saturn or larger. They have now found 3,300, when Kepler's planet candidates are included. 

The new study, conducted by Harvard University graduate student Courtney Dressing and astronomer David Charbonneau at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., casts a new eye on the red dwarfs previously cataloged by the Kepler team. 


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