As astronomers search for exoplanets, those planets could have Earth in sight, study says - CNN

What would they think?"

If life exists outside of Earth and has us in sight, they could use the light of the sun as Earth passes in front of it to look through our atmosphere and understand more about our planet.

The image was taken on February 14, 1990.

The search for life

The observation of a passing of a planet in front of its host star is called a transit, and it's one of the main methods used by astronomers to detect exoplanets using ground and space-based telescopes.

When NASA's James Webb Space Telescope launches next year, it will be used to peer into the atmospheres of exoplanets using this method, and astronomers can use that data to help characterize the atmospheres of exoplanets.

The ecliptic is also essentially the location where exoplanets that have Earth in sight could be found because from their vantage point, they could see Earth as it crosses in front of the sun.

The star systems that could have seen Earth when life first began on our planet are different from the ones that can see the signs of life on our planet now -- as well as the star systems that could see Earth in the future, the researchers wrote in their paper.

"If we found a planet with a vibrant biosphere, we would get curious about whether or not someone is there looking at us too," Kaltenegger said