Dozens of intelligent alien races could be living alongside us in the Milky Way, a study has claimed.
The question of whether there are other life forms within our Universe has long preoccupied scientists.
Now researchers at the University of Nottingham have taken a new approach to estimating the number of possible extraterrestrial civilisations, using the assumption that intelligent life develops on other planets in a similar way as it does on Earth.
They calculate that our galaxy could harbour at least 36 intelligent alien races capable of sending radio signals into space.
But they say the average distance to such civilisations is likely to be 17,000 light-years, making detection and communication ‘very difficult’ with our present technology.
The team developed a new model to estimate the number of intelligent alien races in our galaxy, which they call the Astrobiological Copernican limit.
The model assumes that it takes around five billion years for intelligent life to form on other planets, as on Earth, and that these planets orbit a star with a high metal content just like the Sun.
This differs from traditional techniques, which rely on making guesses of values relating to life, where opinion varies substantially, according to the researchers.
‘Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilisations in our galaxy,’ first author Dr Tom Westby explained.
Christopher Conselice, Professor of Astrophysics at the University of Nottingham, who led the study, said there should be at least ‘a few dozen’ active civilisations in our galaxy.
‘The idea is looking at evolution, but on a cosmic scale,’ he said.
The research shows that the number of civilisations we may be able to detect depends on how long they have been actively sending out signals of their existence into space, such as radio transmissions from satellites or television.
If other technological civilisations have been around for as long as ours, which is currently 100 years, then there will be about 36 ongoing intelligent technical civilisations throughout our Galaxy.
Professor Conselice added that the research also offers important clues about human civilisation’s own ‘future and fate’.
‘Our new research suggests that searches for extraterrestrial intelligent civilisations not only reveals the existence of how life forms, but also gives us clues for how long our civilisation will last,’ he said.
‘If we find that intelligent life is common then this would reveal that our civilisation could exist for much longer than a few hundred years.
‘Alternatively, if we find that there are no active civilisations in our galaxy it is a bad sign for our own long-term existence.’
The study was published today in The Astrophysical Journal.