Astronomers from Cornell's Carl Sagan Institute and Lehigh University have identified exoplanets with a direct line of sight to Earth.
Missions like Kepler and TESS have discovered thousands of exoplanets beyond our solar system, with NASA's James Webb Space Telescope and upcoming Nancy Grace Roman Space Telescope set to uncover even more. This sparks a key question: Could some host life? Recent research explores a twist: Are we visible to them?
Exoplanet detection often uses the transit method, analyzing light curves from stars for periodic dips in brightness caused by orbiting planets passing in front.
In this study, Lisa Kaltenegger of Cornell's Carl Sagan Institute and Joshua Pepper of Lehigh University investigated if Earth's transit across the Sun would be detectable from other worlds—specifically those aligned with Earth's ecliptic plane, the orbital path around the Sun.
The team analyzed over 1,000 stars within potential habitable zones for Earth-like planets, all at about 100 parsecs (326 light-years) from our Solar System.
Proximity matters because Earth is tiny relative to the Sun. For context, Jupiter blocks roughly 1% of sunlight during transit; Earth blocks 100 times less. Only advanced civilizations nearby could detect us with current technology.
Results show many of these exoplanets offer a clear view of Earth. Advanced extraterrestrial civilizations there could even detect biosignatures in our atmosphere, like oxygen or methane.
Most target stars are red dwarfs (29 are Sun-like G-type), and no exoplanets have been confirmed orbiting them yet. Still, the possibility that aliens might spot us first is fascinating.
Findings are detailed in the Monthly Notices of the Royal Astronomical Society.
