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Science in Mind

Closest habitable planets just 13 light-years away

An 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.

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

An 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.

Red-dwarf stars bear little resemblance to our sun. They are about a quarter as heavy and give off a tiny fraction of the energy. If our sun is a powerful light bulb, they are tiny Christmas lights, less than 1 percent as bright. But astronomers at the Harvard-Smithsonian Center for Astrophysics say that solar systems that formed around red dwarfs, which are far more common in our galaxy than stars like the sun, may hold the nearest habitable planets.

At a press conference in Cambridge last Wednesday, scientists said that of the 75 billion red dwarf stars in our galaxy, 6 percent are circled by earth-like planets at a habitable distance that would allow liquid water to exist.

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That means the closest planet hospitable to life is probably 13 light-years away.

The astronomers used data from NASA’s space-based Kepler telescope to make the estimate.

To most people, 13 light-years seems impossibly far. That’s about 76 trillion miles. But to the scientists, who are more used to thinking in galactic scales, this means the search for another earth is getting closer to being in our backyard.

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Courtney Dressing, the astronomer who led the work, said that if the Milky Way were as big as the United States, it would be merely a matter of crossing Central Park in New York City to reach one from here.

That is an exciting way to think about the proximity of life in the universe, but a reality check is in order. For now, scientists are going to try to detect a nearby earth-like habitable world directly.

David Charbonneau, a co-author of the new work, to be published in the Astrophysical Journal, said that astronomers hope to use two powerful telescopes — the James Webb Space Telescope and the Giant Magellan telescope — to find and probe those worlds. They want to detect them first, and then try to understand more about their composition, including what chemicals exist in the atmosphere.

Carolyn Y. Johnson can be reached at cjohnson@globe.com. Follow her on Twitter @carolynyjohnson.
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