‘Earth twin’ likely to be discovered in 2013, scientists say

Planet hunters believe that we will find an ‘alien Earth’ in 2013, Space.com reported.

"The first planet with a measured size, orbit and incident stellar flux that is suitable for life is likely to be announced in 2013," Geoff Marcy, a University of California, Berkeley-based member of the team of scientists who work with NASA’s Kepler Space Telescope, told Space.com.

"I'm very positive that the first Earth twin will be discovered next year," Abel Mendez, who runs the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo, told Space.com.

The third catalog of possible planets identified since the Kepler telescope was switched on in 2009 was released in March and contained 2,321 planet candidates transiting 1,790 stars, Astrobiology magazine reported.

According to Astrobiology magazine:

The Kepler space telescope identifies planet candidates by repeatedly measuring the change in brightness of more than 150,000 stars in search of planets that pass in front, or "transit," their host star.

"With each new catalog release a clear progression toward smaller planets at longer orbital periods is emerging, " Natalie Batalha, Kepler deputy science team lead at San Jose State University in California, told Astrobiology magazine. "This suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant."

Currently, scientist have spotted nine exoplanets that could potentially support human life, including Kepler-22b, discovered in Dec. 2011, which is 2.4 times bigger than Earth and orbiting its star from the right distance, Space.com reported.

More from GlobalPost: Kepler-22b: NASA discovers most 'Earth-like' planet yet (VIDEO)

However, none of these planets are small enough to be alien Earths, according to Space.com. The Earth-sized planets that have been discovered are all located too close to their stars to be habitable.