"I'm very positive that the first Earth twin will be found next year," said Abel Mendez, who runs the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo.
Astronomers found the first exoplanet orbiting a sunlike star in 1995. Since they, they've located more than 800 worlds beyond our own solar system, and many more candidates await confirmation by follow-up observations.
NASA's huges Kepler Space Telescope, for example, has flagged more than 2,300 potential planets since its March 2009 launch. Only 100 or so have been confirmed to date, but mission scientists estimate that at least 80 percent will end up being the real deal.
The first exoplanet finds were scorching-hot Jupiter-like worlds that orbit close to their parent stars, because they were the closest to detect. But over time, new devices came online and planet hunters honed their methodes, enabling the discovery of smaller and more distantly orbiting planets — places more like Earth.
"The first planet with a measured size, orbit and incident stellar flux that is suitable for life is likely to be announced in 2013," said Geoff Marcy, a veteran planet hunter at the University of California, Berkeley, and a member of the Kepler team. Mendez and Marcy both expect this watershed find will be made by Kepler, which spots planets by flagging the telltale brightness dips caused when they pass in front of their parent stars from the instrument's perspective. Kepler needs to witness three of these"transits" to detect a planet, so its early discoveries were tilted toward close-orbiting worlds (which transit more frequently). But over time, the telescope has been spotting more and more distantly orbiting planets — including some in the habitable zone.
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