“In the search for life in the universe, we ask a slightly different question in this study,” said Lisa Kalteneger, an associate professor of astronomy at Cornell University College of Arts and Sciences and director of the Carl Sagan Cornell Institute, in a video shared by the institution. .
“We ask, who could actually notice us? Who could understand that the Earth is boiling with life from their point of view?”
Kalteneger and Joshua Pepper, associate professors of physics at Lehigh University, have identified more than a thousand stars similar to our sun that may have Earth-like planets that rotate away from those stars where they can maintain liquid water. its surface. This distance is called by astronomers as a habitable zone.
To be clear, such planets have not yet been discovered or confirmed around these stars.
And these potential planets, 300 light-years from Earth, could have a direct view of the Earth and the life that thrives on it.
“It takes a precise place for the Earth to move in front of its star, the sun. And then once a year, if you see the Earth go in front of the sun from your point of view, the sun will be just a little less bright,” Kalteneger said. .
“And so you would know that the planet orbits it. And you would also know that it is at the right distance so that there can be liquid water, one of the key ingredients for life.
“So we’ve identified the thousands of nearest stars within 300 light-years, roughly speaking, who might already be able to spot us. Maybe there’s life in the universe there. Maybe they’ve already spotted us. What would they think?”
If life exists outside the Earth and is in our eyes, they could use the light of the sun as the Earth passes in front of it to look through our atmosphere and learn more about our planet.
“Pale Blue Dot” is the name of an iconic image that Cornell astronomer Carl Sagan suggests that NASA’s Voyager 1 spacecraft takes the Earth 3.7 billion miles as the spacecraft moves to the edge of the solar system. The image was taken on February 14, 1990.
The search for life
Observing the passage of a planet in front of its star is called transit, and it is one of the main methods used by astronomers to detect exoplanets using terrestrial and space telescopes.
When NASA’s James Webb Space Telescope launches next year, it will be used to peek into the atmosphere of exoplanets using this method, and astronomers can use this data to help characterize the atmospheres of exoplanets.
And NASA’s Exoplanet Transit Satellite (TESS) mission, which is observing the brightest nearby stars since its launch in 2018, will begin a new phase of its mission in 2021. The mission will search for exoplanets in the ecliptic, which is the plane of the Earth’s orbit around the sun. The TESS spacecraft will essentially turn sideways to observe more of the sky.
The list of stars compiled by the researchers, created by the TESS star catalog, can be used as targets for searching for transiting exoplanets.
In essence, the ecliptic is also the place where exoplanets can be found that have Earth in their field of vision, because from their point of view they could see the Earth when it crosses in front of the sun.
“Only a very small fraction of the exoplanets will simply be randomly aligned with our line of sight so we can see them in transit,” Pepper said.
The star systems that could have seen Earth when life first began on our planet are different from those that can see the signs of life on our planet now – as are the star systems that could see Earth in the future. , the researchers write in their paper.
“If we find a planet with a living biosphere, we would be curious if anyone is watching us or not,” Kalteneger said. “If we’re looking for an intelligent life in the universe that could find us and may want to connect with us, we’ve just created a star map of where to look first.”