'More than 30' active alien civilisations could exist in Milky Way, study suggests

Researchers say the findings could hold key to the survival of civilisation on Earth
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Ewan Somerville15 June 2020

The Milky Way could be home to dozens of alien civilisations, according to a major new study.

Researchers at the University of Nottingham estimated how many planets in our galaxy are hospitable to life using the assumption that life forms on other planets in a similar way to Earth.

The team then matched this to known planets with a similar evolution and found there could be more than 30 “active” communicating so-called intelligent civilisations in the Milky Way.

“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," Professor of Astrophysics Christopher Conselice, who led the research, said.

The Milky Way could be home to dozens of alien worlds, the researchers found
PA

“The idea is looking at evolution, but on a cosmic scale. We call this calculation the Astrobiological Copernican Limit."

There are two forms of Astrobiological Copernican limits. The first - the “weak” limit - suggests that intelligent life takes at least five billion years to form on a planet.

The second - the “strong” limit - suggests it can develop in less than five billion years.

By a strong limit, where a metal content equal to that of the Sun is needed, the researchers calculated that there should be around 36 active civilisations in the Milky Way.

However, the paper, published on Monday in The Astrophysical Journal, shows that we may not know for certain whether these civilisations exist and where they are, unless they are technologically developed.

Locating their existence depends strongly on how long they are actively sending out signals into space, including transmissions from satellites, radios and television.

If these “technological civilisations” last as long as Earth - 100 years - then the researchers estimate 36 intelligent technical civilisations could exist, but estimate the average distance to these would be 17,000 light years, making detection difficult.

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A light year is the distance that light travels in a year, at the speed of light.

Prof Conselice added: "Our new research suggests that searches for extraterrestrial intelligent civilizations not only reveals the existence of how life forms, but also gives us clues for how long our own civilization will last.

“If we find that intelligent life is common then this would reveal that our civilization could exist for much longer than a few hundred years, alternatively if we find that there are no active civilizations in our Galaxy it is a bad sign for our own long-term existence.

“By searching for extraterrestrial intelligent life - even if we find nothing - we are discovering our own future and fate.”

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