Over the past decade, astronomers have discovered many exoplanets potentially suitable for life. This fact has led scientists to ask: Could hypothetical aliens living on exoplanets have detected our presence on Earth?
“From the point of view of the inhabitants of the outer planets, the aliens are us. With this in mind, we decided to find out which exoplanets’ observations allow us to see Earth,” said Lisa Kaltenegger, an astronomer at Cornell University (United States). The researcher added that Earth can be detected from exoplanets by the same method as exoplanets from Earth – transit.
Scientists used data from the Gaia Observatory to identify more than two thousand stellar systems within a hundred parsecs of the Sun from which signs of life on Earth can be detected. “The closest such exoplanet is Ross 128 b. It is not visible from Earth, and our planet is probably not visible from Ross 128 b either, but there was a period of 3,000 years that ended 900 years ago when hypothetical aliens from Ross 128 b could see Earth,” Kaltenegger says.
The planets of the Teegarden system will be the place from which Earth can be seen in 29 years. Inhabitants of the Trappist-1 system, which is only 45 light-years away, will be able to detect Earth by transit in 1,642 years.