"Our Milky Way galaxy is home to hundreds of billions of stars, but until recently astronomers could only guess as to how many are hospitable for the development of complex life," Charles Lineweaver, from University of New South Wales, said in a statement on Friday. 

"What we have done for the first time is to quantify carefully where complex life is likely to exist." Lineweaver and Swinburne University of Technology colleagues Yeshe Fenner and Brad Gibson, in a paper published in the journal Science, said hundreds of stars capable of supporting life are visible from Earth by the naked eye. 

"A few billion stars out there sit in what we call the Galactic Habitable Zone where they have the appropriate conditions to support complex life," Gibson said. 

Terrestrial planets

"Many, many hundreds of those stars which you could look up and see with the naked eye, most of which are actually very close, would potentially have terrestrial planets similar to the earth and Mars and Venus." 

Gibson said the habitable zone appeared about eight billion years ago but had since accumulated heavy elements like carbon, oxygen and iron. 

"Perhaps there is no life out there," Lineweaver said. "But if there is life, we have determined where you are most likely to find it."