The rapid pace of exoplanet discoveries suggests that the first Earth twin will be found relatively soon, according to researchers, adding that the first true "alien Earth" could be found in 2012.

2011 brought the tally of confirmed exoplanets reached more than 700, with NASA's Kepler space telescope finding thousands of additional candidates that still needs verification. 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.

Only 33 of these potential planets have been confirmed by follow-up observations, but astronomers estimate that at least 80 percent of them will turn out to be the real deal.

Researchers said that with these recent discoveries, 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, they 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."

In addition to finding the true "alien Earth," astronomers are also looking into diversity of alien worlds and systems. One planet was found to be as light and airy as Styrofoam, while another was as dense as iron. The Kepler team has also announced the discovery of an alien planet that circles two suns.

Astronomers have also confirmed several planets in their stars' habitable zones, although none can be considered true alien Earths yet. But the search for Earth's twin may bear fruit as early as next year, researchers say.

Launched in March 2009, the Kepler space telescope hunts for alien planets using a technique known as the transit method. According to researchers, the longer Kepler operates, the better its chances of detecting an Earth-like world, and now that the instrument is on its third year, the finds are getting more interesting.

Batalha said that so far none of the exoplanets have been both Earth-size and in their stars' habitable zone, adding that this could change with the next announcement of Kepler candidates, which might come in June or July