Our galaxy may have more than 30 intelligent alien civilizations

More than 30 intelligent alien civilizations could exist in the Milky Way, according to a new study in The Astrophysical Journal.

The big picture: Scientists have long tried to estimate how many alien civilizations like our own could be out in the universe.

• The Drake Equation is most famous, but the new study uses a simple way to estimate exactly how many intelligent civilizations could be lurking in our galaxy.

What they did: The new study uses Earth as a model for how life may form in other parts of 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," Christopher Conselice, co-author of the study, said in a statement. "The idea is looking at evolution, but on a cosmic scale."
• The new estimate factors in the likelihood that stars host Earth-like planets in their habitable zones and the history of star formation throughout the galaxy.
• Under the study's strictest set of assumptions — which includes that stars that could host planets with intelligent life be similar in metal content to our Sun — the authors expect there should be 36 alien civilizations in the galaxy.

But, but, but: Even if there were three dozen intelligent civilizations in our galaxy, there's no guarantee that we'll ever interact with any of them.

• According to the study, on average, these civilization are likely about 17,000 light-years away.