By Alex Fox/Smithsonianmag.com
Astronomers on Earth can discover far away planets by watching the light of distant stars and waiting to see if that light ever wavers as an orbiting alien world passes by. But as Nadia Drake reports for National Geographic, a new study turns a hypothetical extraterrestrial telescope back on Earth.
Astronomer Lisa Kaltenegger of Cornell University, lead author of the study published this week in the journal Nature, posed the question: “Which stars could see us as the aliens, as the transiting planet where the Earth blocks out light from the star?”
By analyzing the shifting cosmic lines of sight for more than 300,000 stars within about 300 light years of our sun, Kaltenegger and her co-author identified more than 2,000 stars with the right vantage to have detected Earth sometime in the last 5,000 years—or in the next 5,000 years to come.
For example, a mere 12 lightyears away from us there are two planets roughly the size of Earth winding their way around Teegarden’s star, reports Nell Greenfieldboyce for NPR. By astronomers’ reckoning, these worlds could be hospitable enough to potentially support life.