40,000 needles in the galactic haystack

Three scenarios of how life could develop were also taken into account.

The first – that it is difficult for life to form but easy for it to evolve – concluded there are at least 361 planets harbouring intelligent life. The second, which assumed that life is easily formed but struggles to develop further, came up with a total of 31,513.

The third scenario, which assumes that life can be passed from planet to planet with the help of asteroids, saw the total rocket to almost 38,000, the Journal of Astrobiology reports.