Scientists have spent the past few years exploring the universe around us and searching for signs of life (intelligent or otherwise). Now, in a shining moment of introspection, scientists have realized that many of the exoplanets we’ve discovered might have also discovered us.
A new paper—written by astronomers from Cornell University and the American Museum of Natural History and published in Nature on June 23—centers on that very thought. Its authors found roughly 2,000 star systems that would have had a perfect vantage point for detecting our planet using the same method we use to detect exoplanets—by watching for a dip in light as a planet transits “in front of” its host star. That number might seem high, but that would be how many could have potentially spotted Earth since the days of early human civilization, approximately 5,000 years ago.
“I started to wonder what stars could see us if we change the vantage point … The cosmos is dynamic, so the vantage point is not forever—it is gained and lost,” said Lisa Kaltenegger, associate professor of astronomy at Cornell and the paper’s co-author to The Verge. “And I was wondering how long that front row seat to find Earth through the dip in brightness of the star lasts. No one knew.”
Precisely 1,715 stars roughly 326 light-years away have literally been in the right place at the right time: able to spot Earth, and possibly even life on it. The report relied on data on stars detected by the European Space Agency’s Gaia spacecraft and revealed that an impressive 1,402 of them can currently see Earth from an area dubbed the Earth Transit Zone.
Researchers of a separate paper have also noted the likelihood of this reciprocal perspective, stating, “If any of these planets host intelligent observers, they could have identified Earth as a habitable, or even as a living, world long ago, and we could be receiving their broadcasts, today.” That study was published in Astrobiology in 2015.
Kaltenegger and her co-author, Jackie Faherty, are widening that time frame, however, looking both backward and forward. They noted that 313 star systems were in just the right place to watch Earth transit in front of the Sun in the last 5,000 years. They also pointed out that any of the exoplanets within the Trappist-1 system—which has the largest group of Earth-size planets within the habitable zone—will most likely be able to see Earth 1,642 years from now.
Of course, we don’t yet know if there are intelligent beings living on any of those planets (or if they have the same technology as us, or if they’ve discovered us, or care about us). All we know now is that those planets exist, and many of them have the potential for life of some kind.
Regardless, scientists are still working on detecting other planets and exploring the universe at large via the Hubble Space Telescope and (hopefully) the James Webb Telescope that’s slated to (finally) launch later this year. The more resources we have to explore and detect, the more data we can pull in to study and learn from regarding life and literally everything else in the universe.
via The Verge