The search for planets going around other stars by instruments like the Kepler space telescope and the Transiting Exoplanet Survey Sattellite, or TESS , have turned up more than 4, planets just in our cosmic backyard.
It is beginning to look like most stars have at least one planet going around them, and with up to billion stars in the Milky Way, that could mean on the order of a trillion planets in our galaxy alone. And there are hundreds of billions of other galaxies spread across the universe.
However, many of the planets discovered so far are gas giants like Jupiter, as close to their stars as Mercury is to the sun, or far away, making them super cold like Pluto.
What we need to find are Earth-sized planets going around sun-type stars at just the right distance so liquid water can exist on the surface. Another study out of the University of British Columbia looked at the number of sun-like stars in the galaxy and estimated that one in five of them could have an Earth-like planet , which brings the number down to sx billion.
So that's a lot of planets that could have someone interesting living on them that we might want to talk to. The University of Nottingham team took this one step further suggesting that if we want to find something more intelligent than alien bacteria, or the equivalent of plants or simple animals, then you have to wait for intelligent life to evolve.
Since it took nearly five billion years for intelligent life to evolve on Earth to the point where it had communications technology, they figured that might be a reasonable average. Then they assumed that these civilizations retained that capacity for about years — again about as long as we've had it. Taking this into account, they calculated that a mere 36 plus or minus intelligent, communicating civilizations might exist right now. That's a very small number to be spread out across a very large galaxy.
According to a new study in The Astrophysical Journal , scientists at the University of Nottingham estimate that there is a minimum of 36 communicating intelligent alien civilizations in the Milky Way galaxy. They say the estimate is actually conservative — it's based on the assumption that intelligent life forms on other planets in a similar way to how it does on Earth, using what they call the Astrobiological Copernican Limit.
The researchers assume that Earth is not special — if an Earth-like planet forms in an Earth-like orbit around a Sun-like star, hosting a civilization that develops technologically in a similar way to humans, there would be approximately 36 Earth-like civilizations in our galaxy.
In this case, other technological civilizations would be sending out signals, such as radio transmissions from satellites and televisions, on a similar timeline as humans, also attempting to find other lifeforms.
Previous calculations of alien life have been based on the Drake equation , which includes seven factors needed to find the number of intelligent civilizations, written by astronomer and astrophysicist Frank Drake in The estimates have been extremely broad, ranging from zero to a few billion civilizations. The team of researchers in Nottingham refined the equation using new data and assumptions. In fact, scientists think that there could be 3.
How big is that number? Well, that means there are more than a million planets in the universe for every single grain of sand on our planet. There are simply so many places that could have life that I, personally, think there must be a ginormous number of inhabited planets through the universe.
Probably billions, trillions, or even quadrillions! Hello, curious kids! Ask an adult to send your question to us. You can:. Please tell us your name, age and which city you live in.
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