London: Recent discoveries of exoplanets have rekindled hope for other advanced technological civilisations that may have ever existed near us, researchers have found.

A new paper shows that unless the odds of advanced life evolving on a habitable planet are astonishingly low, then human kind is not the universe's first technological or advanced civilisation.

“We have known for a long time approximately how many stars exist. We didn't know how many of those stars had planets that could potentially harbour life or how often life might evolve and lead to intelligent beings,” explained Adam Frank, professor of physics and astronomy at University of Rochester.

“Thanks to NASA's Kepler satellite and other searches, we now know that roughly one-fifth of stars have planets in "habitable zones," where temperatures could support life as we know it. So one of the three big uncertainties has now been constrained,” he added.

The big question - how long civilisations might survive - is still unknown. 

“The fact that humans have had rudimentary technology for roughly 10,000 years doesn't really tell us if other societies would last that long or perhaps much longer," Frand noted in a paper to be published in Astrobiology.

Using a novel approach, Frank and Woodruff Sullivan from University of Washington calculate how unlikely advanced life must be if there has never been another example among the universe's ten billion trillion stars, or even among our own Milky Way galaxy's hundred billion.

The result? By applying the new exoplanet data to the universe's 2 x 10 to the 22nd power stars, the team found that human civilisation is likely to be unique in the cosmos only if the odds of a civilisation developing on a habitable planet are less than about one in 10 billion trillion, or one part in 10 to the 22th power.

Another technological species likely has evolved on a habitable planet in our own Milky Way galaxy if the odds against it are better than one chance in 60 billion.

The universe is more than 13 billion years old.

That means that even if there have been a thousand civilisations in our own galaxy, if they live only as long as we have been around -- roughly 10,000 years -- then all of them are likely already extinct. 

“And others won't evolve until we are long gone. For us to have much chance of success in finding another "contemporary" active technological civilization, on average they must last much longer than our present lifetime,” the author noted.