Aliens Will be Found by 2040'
An artist's impression of a planet orbiting the yellow, sun-like star HD 209458, 150 light-years from earth. REUTERS/NASA

Human civilisation may come into contact with extraterrestrial life within the next 25 years, a top US scientist has predicted.

Alien hunters expect to discover alien beings by the year 2040, according to Seth Shostak, a senior astronomer at SETI (Search for Extraterrestrial Intelligence) Institute at Stanford University, California.

Shostak made the claims while speaking at NASA Innovative Advanced Concepts (NIAC) Symposium in California.

The aliens will be found by detecting alien-produced electromagnetic signals in space, according to Shostak.

"I think we'll find ET (extraterrestrials) within two dozen years using these sorts of experiments," Shostak said, on space and astronomy news website

He also said that by 2040 astronomers will have scanned enough star systems to detect those signals.

"Instead of looking at a few thousand star systems, which is the tally so far, we will have looked at maybe a million star systems 24 years from now. A million might be the right number to find something," added Shostak.

Shostak's prediction follows progress made by Nasa's planet-hunting Kepler space telescope, which has provided evidence that the Milky Way galaxy does have Earth-like worlds capable of supporting life.

According to Kepler's finding, about 10% of the known planets circling suns in the galaxy resemble Earth, which increases the possibility that alien life exists elsewhere.

"The bottom line is, one in five stars has at least one planet where life might spring up. That's a fantastically large percentage. That means in our galaxy, there's on the order of tens of billions of Earth-like worlds," said Shostak.

Shostak strongly believes that at least some of these worlds have "intelligent" aliens who, just like humans, are able to send electromagnetic signals out into the cosmos.