"Assuming that 1:10, 000 are similar to the Earth would give us 5, 000, 000 such planets, " added Tuomi, who led teams reporting the discovery of several potentially habitable planet candidates this year, including an exoplanet orbiting the star Tau Ceti just 11.9 light-years from Earth.

MSN: Senior writer

It's been 50 years since Philip Morrison and Guiseppe Cocconi published their seminal scientific paper on SETI in the journal Nature, and since Frank Drake first used the Tatel telescope in Green Bank, West Virginia, to attempt to detect any radio signals from technologies he thought could be orbiting the nearby stars of Tau Ceti and Epsilon Eridani.

CNN: What if there's somebody else out there?