Two astronomers tracked the star systems that, if they had life, could look toward us and discover our planet the same way we detect others.
For astronomers, a tiny blip in data can signal the existence of an entire world. It happens when a planet far beyond our solar system passes in front of its own star. The planet blocks a tiny bit of light, making the shining star appear fainter to us. Scientists have used these moments to discover thousands of exoplanets in the Milky Way—icy planets and lava planets, hot Jupiters and miniature Neptunes, planets with a thick atmosphere and planets with no atmosphere at all. A whole array of mysterious, distant worlds, all orbiting their own sun.
Which raises the question: Can anyone else find us the same way?
It’s a spooky thought—spooky enough that when I first considered it, I jolted upright in my desk chair and looked around the room, as if aliens could somehow see me. Earth circles its own star as dutifully as all those exoplanets do, and alien astronomers, if any existed, could theoretically detect the presence of our planet in the slight dimming of our sun, a blip in the data. From the perspective of those other planets, “the aliens are us,” says Lisa Kaltenegger, an astronomer and the director of the Carl Sagan Institute at Cornell University. Chills again!