New Study suggests Alien Civilizations may number in trillions

“We really do know that pretty much every star in the sky hosts at least one planet…” – astronomer Adam Frank.

Rejoice Alien hunters, the possibility that Earth is not the only planet inhabited by an intelligent civilization has gained more credibility thanks to a brand new study that coincides with NASA’s recent planetary discoveries. The new study, published in the Journal Astrobiology proposes that more planets in our galaxy harbor advanced civilizations than anyone previously imagined.

“We really do know that pretty much every star in the sky hosts at least one planet,” said astronomer Adam Frank co-author of the study.

Woodruff Sullivan and Adam Frank looked at NASA’s recent discoveries of potentially habitable worlds and considered the odds whether sophisticated civilizations could have inhabited them or still do.

“What we showed was the ‘floor’ on the probability for a civilization to form on any randomly chosen planet,” Frank, a University of Rochester physics and astronomy professor, told The Huffington Post in an email. “If we are the only civilization in cosmic history, then that what we calculated is the actual probability nature has set. But if the real probability is higher than that floor, then civilizations have happened before.” 

According to Frank, the potential number of planets orbiting their host star within a habitable distance is staggering.

This raises hopes that one of those planets might host alien life, and with a bit of luck, we even might discover an advanced alien civilization inhabiting one of those planets.

If we’re the only place with intelligent life, then we’ve really won the mother of all lotteries.” -Seth Shostak, SETI Institute senior astronomer. Image Credit

“Even if you are pretty pessimistic and think that you’d have to search through 100 billion (habitable zone) planets before you found one where a civilization developed, then there have still been a trillion civilizations over cosmic history!” Frank wrote. “When I think about that, my mind reels — even if there is just a one in a 100 billion chance of evolution creating exo-civilizations, the universe still has made so many of them that we are swamped by histories other than our own.”

The Drake equation

One of the most famous equations dealing with the possibility of Alien life existing in the universe is the Drake Equation. It was created by astronomer Frank Drake in 1961, and it estimates the number of planets that may be home to advanced alien civilizations with the ability to communicate with other civilizations in the cosmos.

However, Frank and Sullivan modified the Drake equation implementing new data into it. Since the Drake equation analyzes the possibility od advanced civilizations existing in the Milky Way, the equation proposed by Frank and Sullivan calculate the possible number of advanced alien civilizations that have existed in our galaxy throughout the whole ‘known’ history of the universe.

The odds that no one is out there are very, very small. Image Credit

With all the suitable real estate that’s out there, if we’re the only place with intelligent life, then we’ve really won the mother of all lotteries.” –Seth Shostak, SETI Institute senior astronomer.

Scienitsts consider the following when attempting to come up with numbers of Extraterrestrial worlds:


The number of civilizations in Galaxy whose electromagnetic emissions are detectable.


The rate of formation of stars suitable for the development of intelligent life, in stars per year.


The fraction of those stars with planetary systems.


The number of planets, per solar system, with an environment suitable for life.


The fraction of suitable planets on which life actually appears.


The fraction of life bearing planets on which intelligent life emerges.


The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.


The length of time such civilizations release detectable signals into space, in years.


Writing in the Astrobiology study, Frank and Sullivan state:

“ Recent advances in exoplanet studies provide strong constraints on all astrophysical terms in the Drake equation. Using these and modifying the form and intent of the Drake equation, we set a firm lower bound on the probability that one or more technological species have evolved anywhere and at any time in the history of the observable Universe.” (source)

The two researchers write about what they call: “the cosmic frequency of technological species.”

“The universe is more than 13 billion years old,” Sullivan, of the astronomy department and astrobiology program at the University of Washington, said in a statement. “That means that even if there have been 1,000 civilizations in our own galaxy, if they live only as long as we have been around — roughly 10,000 years — then all of them are likely already extinct. And others won’t evolve until we are long gone.

“For us to have much chance of finding another ‘contemporary’ active technological civilization, on average they must last much longer than our present lifetime,” Sullivan said. (source)

We have searched for traces of advanced alien civilizations, in hopes of finding out we are not alone for decades.

“With so many stars and planets filling the cosmos, it boggles the mind to think that we’re the only clever life to have made an appearance,” SETI Institute senior astronomer Seth Shostak told HuffPost in an email. “Frank and Sullivan use new research indicating that roughly one in five stars is orbited by a planet that could nurture biology. After that, it’s just a matter of counting up the tally of stars in the visible universe, and saying that — with all the suitable real estate that’s out there, if we’re the only place with intelligent life, then we’ve really won the mother of all lotteries.

However, Shostak tells us not to be overly optimistic or pessimistic about the SETI Institutes search for intelligent signals from our cosmic neighbors.

“The odds that no one is out there are very, very small. It’s a bit like an ant coming out of its hive, seeing the enormous amount of real estate stretching in all directions and deciding that, if its home is the only ant hill, then its existence is a near-miracle,” said Shostak in an interview with HuffPost.

Journal reference:


A New Empirical Constraint on the Prevalence of Technological Species in the Universe.

Leave a Reply

Your email address will not be published.