Magazine article Science News

Exoplanet Trio Could Harbor Life: Worlds Orbiting Cool Star Are Good Place to Look for Aliens

Magazine article Science News

Exoplanet Trio Could Harbor Life: Worlds Orbiting Cool Star Are Good Place to Look for Aliens

Article excerpt

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Three Earth-sized planets orbiting a star practically next-door might be a good place to hunt for alien life--or at least to check out some worlds that are different from anything in our solar system.

The planets orbit a dim, cool star just 39 light-years away in the constellation Aquarius. Each is outside or possibly on the edge of the star's habitable zone--where average temperatures are just right for liquid water. But there could be niche locales on these worlds where alien life might thrive, Michael Gillon, an astrophysicist at the University of Liege in Belgium and colleagues report online May 2 in Nature.

On the two inner planets, a year lasts just a couple of days. Data on the third world are sparse; it could take anywhere from 4.5 to 72.8 days to trek around its sun. The star, designated 2MASS J23062928-0502285, is about the size of Jupiter--about one-tenth as wide as our sun--and about 3,200 degrees Celsius cooler than the sun. Such runts make up about 15 percent of the stars in the galaxy, though astronomers had not found planets around one before. All three planets were discovered as periodic dips in starlight in late 2015 using TRAPPIST, a telescope at La Silla Observatory in Chile.

If anything does crawl or grow on these worlds, it bathes in mostly infrared light. The innermost planets receive several times as much energy from their star as Earth does from our sun, which technically puts them outside the star's habitable zone (SN: 4/30/16, p. 36). But the planets are huddled up so close to the star that gravity might keep one side of the planets permanently facing the star, creating a temperate zone along the line where day turns to night, the researchers say.

Faint red stars such as this one are the best place to look for warm rocky planets, says Nicolas Cowan, an astronomer at McGill University in Montreal. …

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