Thursday, February 13, 2014

Alien Earths: why life on other worlds would be far weirder than us

And you thought your planet was strange

Last month, the American Astronomical Society's 223rd meeting featured the announcement of a few breakthroughs: Using the Kepler space observatory, researchers had discovered a planet roughly the mass of Earth orbiting a star beyond our solar system, and with the Hubble telescope they had provided the first detailed look at the weather of a "super Earth" — a planet larger than ours but smaller than Neptune — in our galactic neighborhood. Astronomers found that GJ 1214b, like much of the Earth on any given day, is cloudy.

These similarities to Earth are tantalizing. But despite them, these planets' respective solar systems look nothing like our own. Rather than circling a big, hot, yellow sun like ours, they spin around small, cool, red stars called red dwarfs. Kind of like Krypton. Although not visible to the naked eye from Earth, these red dwarfs are the most populous stars in the Milky Way. And over the last year, a flurry of research has shown that red dwarf stars are also the best targets in the search for exoplanets that might support life. Right now the chances that a red dwarf star has a planet orbiting in its habitable zone, an astronomical goldilocks area neither too hot nor too cold for liquid water, are better than for a star like our sun. Research also suggests that these planets (and maybe life on them) behave in ways that, from our Earth-centric view, seem bizarre.

"The first planet on which we'll be able to discover signs of life is most likely going to be orbiting a red dwarf," says Courtney Dressing, an astronomy graduate student at Harvard.

Dressing and her advisor David Charbonneau kicked off the series of recent discoveries last February with a look at data from NASA's Kepler telescope. Using what Dressing calls "conservative" estimates for the habitable zone around red dwarfs, they came up with an occurrence rate of 15 percent — meaning that one in six of the most common type of star in the galaxy had a potentially habitable planet. That's no small result, but it proved to be only a starting point.

"I just jumped out of my chair."
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