A group of researchers from Australia and Denmark led by Dr Charley Lineweaver of the Australian National University has calculated that there are hundreds of billions of Earth-like planets in the Milky Way Galaxy, by applying a 200-year-old idea to the thousands of exoplanets discovered by NASA’s Kepler Space Telescope.
“The ingredients for life are plentiful, and we now know that habitable environments are plentiful,” said Dr Lineweaver, who is a co-author on the paper submitted for publication in the Monthly Notices of the Royal Astronomical Society.
“However, the Universe is not teeming with aliens with human-like intelligence that can build radio telescopes and space ships.”
“Otherwise we would have seen or heard from them,” he added.
“It could be that there is some other bottleneck for the emergence of life that we haven’t worked out yet.”
“Or intelligent civilisations evolve, but then self-destruct.”
The Kepler space telescope is biased towards seeing planets very close to their stars, that are too hot for liquid water, but the scientists extrapolated from Kepler’s results using the theory that was used to predict the existence of Uranus.
“We used the Titius-Bode relation and Kepler data to predict the positions of planets that Kepler is unable to see,” Dr Lineweaver explained.