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Why 2012 could be the year we find a habitable planet

Other than the one we're currently living on, that is. As discoveries of alien planets accelerates, the discovery of an "alien Earth" could be just over the horizon. 

By Mike WallSPACE.com / December 21, 2011

An artist's illustration of Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star, is seen in this undated handout picture released by NASA.

NASA/Ames/JPL-Caltech/Reuters

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While 2011 was a huge year for alien-planet discoveries, 2012 could bring something even more exciting: the first true "alien Earth."

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This year saw the tally of confirmed exoplanets top 700, with NASA's Kepler space telescope flagging thousands of additional candidates that still need to be verified. And just this month, Kepler scientists announced two landmark finds — the first two Earth-size alien planets, as well as a larger world in its star's habitable zone, that just-right range of distances where liquid water (and possibly life as we know it) could exist.

These and other recent discoveries suggest that the prized quarry of many exoplanet hunters — an "alien Earth" — could be just over the horizon. In fact, such a planet may well pop up in the next round of Kepler candidates, which should be released next year, researchers said.

"I'm guessing that this next planet catalog is going to see, finally, some numbers of points that are really, truly Earth-sized and in the habitable zone," said Natalie Batalha, deputy leader of the Kepler science team at NASA's Ames Research Center in Moffett Field, Calif. "That's something that I really look forward to, is getting those candidates." [Vote Now! Most Intriguing Alien Planets of 2011]

Alien planets piling up

The year has seen a huge increase in the number of known exoplanets. At the start of 2011, astronomers had confirmed 528 alien worlds, according to the Extrasolar Planets Encyclopedia, a database compiled by astrobiologist Jean Schneider of the Paris-Meudon Observatory.

Less than one year later — and just 16 years after the first alien planet was found orbiting a sun-like star — the count now stands at 713. And thousands more are waiting in the wings.

On Dec. 5, Kepler scientists announced the discovery of 1,094 new exoplanet candidates, bringing the mission's total tally in its first 16 months of operation to 2,326. So far, just 33 of these potential planets have been confirmed by follow-up observations, but researchers have estimated that at least 80 percent of them will turn out to be the real deal.

These huge numbers are exciting by themselves, but the search for alien planets isn't really about increasing the tally. Rather, it's a quest to better understand the nature and diversity of alien worlds, researchers say.

"You can only understand the diversity of systems if you have enough numbers that speak to the statistics," Batalha told SPACE.com. "You really want a large sample, and that's where Kepler's going to make a huge contribution."

The diversity of alien worlds and systems appears to be high. Astronomers have found one planet as light and airy as Styrofoam, for example, and another as dense as iron. And in September, the Kepler team announced the discovery of an alien planet that circles two suns, like Luke Skywalker's home planet of Tatooine in the "Star Wars" films.

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