There Are At Least 36 Intelligent Alien Civilizations In Our Galaxy, Say Scientists

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There Are At Least 36 Intelligent Alien Civilizations In Our Galaxy, Say 
Scientists
Jamie Carter Senior Contributor

I write about science and nature, technology and travel, stargazing and 
eclipses.
This artist’s impression shows the planet K2-18b, it’s host star and an 
accompanying planet in this system. K2-18b is now the only super-Earth 
exoplanet known to host both water and temperatures that could support life.

It’s the oldest and the greatest cosmic question of all: is there 
anybody out there?

For years all we’ve had is the Drake Equation to help us understand the 
question, but no indication of an answer. Now a group of scientists at 
the University of Nottingham think they’ve come up with a new “cosmic 
evolution”-based calculation that says that there are likely to be at 
least 36 ongoing intelligent civilizations in our Milky Way galaxy.

The Milky Way, home to our Solar System, is estimated to have 100 
billion to 400 billion stars, and roughly one exoplanet per star in our 
galaxy.

Published today in The Astrophysical Journal, the new paper examines the 
likely number of Communicating Extra-Terrestrial Intelligent (CETI) 
civilizations in the Milky Way. It assumes that intelligent life comes 
to occur on other planets much as it has done on our own planet.

A key assumption is that it takes around five billion years for 
intelligent life to form on other planets, as it does on Earth. Another 
is that a technological civilization will last at least 100 years—as 
ours has, thus far. After all, it took 4.5 billion years of evolution 
before a technological civilization arose on Earth, and was capable of 
communicating.

The number of civilizations depends strongly on how long they are 
actively sending out signals of their existence into space—such as radio 
transmissions from satellites and TV.

The calculation—which says that there could be 36 active communicating 
intelligent civilizations in our home galaxy—is called the 
“Astrobiological Copernican Limit” by the researchers. It takes into 
account:

star formation histories.
how common metal-rich stars are (like the Sun).
the likelihood of stars hosting Earth-like planets in their habitable zones.

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“The classic method for estimating the number of intelligent 
civilizations relies on making guesses of values relating to life, but 
opinions about such matters vary quite substantially,” said Tom Westby, 
Assistant Professor, Faculty of Engineering at the University of 
Nottingham, and lead author on the paper. “Our new study simplifies 
these assumptions using new data, giving us a solid estimate of the 
number of civilizations in our galaxy.”

The estimation of at least 36 civilizations is actually the most 
conservative lower limit using the strictest set of assumptions—namely 
that communicating civilizations only survive for 100 years.

However, the authors note that the average distance to one of these 36 
civilizations is around 17,000 light-years, so detection and 
communication is currently impossible.

There’s also the thorny question of how long intelligent civilizations 
tend to survive.

“Searches for extraterrestrial intelligent civilizations not only 
reveals the existence of how life itself forms, but also gives us clues 
about how long our own civilization will last,” said Christopher 
Conselice, Professor of Astrophysics at the University of Nottingham, 
who led the research. “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.”

Wishing you clear skies and wide eyes.


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other work here.
Jamie Carter
I'm an experienced science, technology and travel journalist interested 
in space exploration, moon-gazing, exploring the night sky, solar and 
lunar eclipses,… Read More