In the search for extraterrestrial life, we’re usually the ones doing the snooping. But Lisa Kaltenegger, an astronomer at Cornell University, wan

This Is How Aliens Might Search for Human Life

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2021-07-13 14:00:08

In the search for extraterrestrial life, we’re usually the ones doing the snooping. But Lisa Kaltenegger, an astronomer at Cornell University, wanted to know who out there might be watching us. “For whom would we be the aliens?” she asks.

So Kaltenegger enlisted the help of Jackie Faherty, an astrophysicist who works at Hayden Planetarium, part of the American Museum of Natural History, in New York City. Together, they took on the task of identifying stars that might host alien worlds where the residents—past, present, or future—would have a chance of detecting Earth as a transiting exoplanet. That means their planet would have just the right vantage point to observe a slight dip in the brightness of our sun as Earth crosses, or transits, in front of it. This is the most successful method we Earthlings use to find planets beyond our solar system as they orbit around their own host stars, creating tiny blips in the light we can see with astronomical instruments.

In June, Kaltenegger and Faherty announced their results in Nature with an extensive inventory of stars that have either had, or will later have, the proper orientation to discover our planet. They identified over 2,000 stars, using a time range from 5,000 years ago, when civilizations on Earth first began to bloom, to 5,000 years into the future. Not only does the study provide a resource to exoplanet hunters by pinpointing which stars they should pay attention to, it also gives a unique—and arguably, unsettling—viewpoint of our visibility to the rest of the universe. “I felt spied on a little bit,” Faherty says, remembering the uncanny sensation of being overexposed. “Do I want to be on a planet that can be found?”