There are "at least a few dozen" intelligent alien civilisations in the Milky Way that we've not yet made contact with, exciting new research has estimated.
The study, carried out by University of Nottingham researchers and published in The Astrophysical Journal this week, is described as "an enormous advance" on previous estimates which "spanned from zero [civilisations] to billions".
Lead researcher Professor Christopher Conselice says his team shed new light on the topic by tackling the problem in a different way: by assuming that "intelligent life forms on other planets in a similar way as it does on Earth".
"There should be at least a few dozen active civilizations in our Galaxy under the assumption that it takes 5 billion years for intelligent life to form on other planets, as on Earth," Prof Conselice said.
"The idea is looking at evolution, but on a cosmic scale. We call this calculation the Astrobiological Copernican Limit."
First author Tom Westby says the research team's initial estimates indicate "there should be around 36 active civilisations in our galaxy".
The bad news, however, is that the average distance to these civilisations is 17,000 light years away - a distance that doesn't allow us to detect or communicate with a potential alien colony using our current technology.
Prof Conselice says the search for other life forms could give us clues as to how long our own civilisation can last.
"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," he explained.
"Alternatively, if we find that there are no active civilisations in our galaxy, it is a bad sign for our own long-term existence."
Last year, Carl Sagan Institute scientists posited that alien life might give itself away by giving their planet a fluorescent glow, "leaving us a telltale sign to spot them".
Meanwhile another group of astronomers in the US have set up an array of telescopes that will be looking out for nanosecond-long bursts of light they believe could be a form of interstellar communication.
