Meet GJ 1214b, the most Earth-like planet ever found outside our solar system.
It’s not exactly Earth’s twin: It’s about six times bigger, a whole lot hotter and made mostly of water. But compared to the giant gas balls that account for nearly every other extrasolar planet ever found, it’s pretty darn close. And through a fortunate happenstance of cosmic geometry, astronomers will be able to study GJ 1214b in great detail.
“If you want to describe in one sentence what this planet is, it’s a big, hot ocean,” said Harvard University astronomer David Charbonneau. “We can even study its atmosphere. This planet will occupy us for years. That’s part of what’s so exciting about it.”
Described by Charbonneau and 17 other astronomers in a paper published Wednesday in Nature, GJ 1214b is the latest of roughly 400 planets detected by earthly telescopes. Of these, 28 are considered “super-Earths” — planets with a mass roughly comparable to our own.
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That’s how Corot-7b, a rocky planet with roughly twice the heft of Earth, was spotted in February. Ditto Gliese 581c, identified two months later, and orbiting its star at a distance consistent with human notions of habitability.
Unfortunately, not much more will ever be known about those planets. Corot-7b is 500 light-years away, too distant for our telescopes to discern more detail. And from our viewing angle, Gliese 581c never quite crosses directly in front of its sun, causing photons to warp in ways that would reveal its atmospheric character.
GJ 1214b does pass in front of its sun. Separated from Earth by a distance of just 42 light years, it’s close enough to be studied. Scientists will finally get to look at another Earth-like world.
“Only rarely does a long-sought scientific frontier loom so prominently just beyond the horizon, that the next generation of instruments seems sure to reach it,” wrote Geoffrey Marcey, a University of California, Berkeley astronomer, in a commentary accompanying the findings. “They provide the most-watertight evidence so far for a planet that is something like our own Earth, outside our solar system.”
Based on its radius and mass — about 2.7 and 6.6 times that of Earth’s — Charbonneau and the other astronomers have calculated GJ 1214b’s density. It appears to be composed of extraordinarily deep oceans, surrounding a rocky core.
That's the good news. The bad news is that they're just now starting to recieve our TV waves. In fa few years they'll arive in their space ships demanding to know why Ward was being so rough on the Beaver. =8^O
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http://www.wired.com/wiredscience/2009/12/super-earth/
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