Using data gathered by NASA’s Transiting Exoplanet Survey Satellite (TESS) and ESA’s Gaia satellite, a team of U.S. astronomers has identified 1,004 main-sequence stars that might host potentially habitable Earth-like planets — all within 100 parsecs (about 326 light-years) of Earth — and which should be able to detect Earth’s chemical traces of life.
Kaltenegger & Pepper identified 1,004 main-sequence stars that might contain Earth-like planets in their habitable zones, which should be able to detect Earth’s chemical traces of life. Image credit: Sci-News.com.
“Let’s reverse the viewpoint to that of other stars and ask from which vantage point other observers could find Earth as a transiting planet,” said Dr. Lisa Kaltenegger, an astronomer in the Astronomy Department at Cornell University and director of Cornell’s Carl Sagan Institute.
“If observers were out there searching, they would be able to see signs of a biosphere in the atmosphere of our Pale Blue Dot.”
“And we can even see some of the brightest of these stars in our night sky without binoculars or telescopes.”
But which stars systems could find us? Holding the key to this science is Earth’s ecliptic — the plane of Earth’s orbit around the Sun.
The ecliptic is where the exoplanets with a view of Earth would be located, as they will be the places able to see Earth crossing its own Sun — effectively providing observers a way to discover our planet’s vibrant biosphere.
Dr. Kaltenegger and her colleague, Dr. Joshua Pepper of Lehigh University, created the list of 1,004 main-sequence stars within 100 parsecs, of which 508 guarantee a minimum 10-h long observation of Earth’s transit.
The team’s list consists of about 77% M-type (red dwarfs), 12% K-type, 6% G-type, 4% F-type stars, and 1% A-type stars.
“Only a very small fraction of exoplanets will just happen to be randomly aligned with our line of sight so we can see them transit,” Dr. Pepper said.
“But all of the thousand stars we identified in our paper in the solar neighborhood could see our Earth transit the Sun, calling their attention.”
“If we found a planet with a vibrant biosphere, we would get curious about whether or not someone is there looking at us too,” Dr. Kaltenegger said.
“If we’re looking for intelligent life in the Universe that could find us and might want to get in touch, we’ve just created the star map of where we should look first.”
The results were published in the Monthly Notices of the Royal Astronomical Society: Letters.
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L. Kaltenegger & J. Pepper. 2020. Which stars can see Earth as a transiting exoplanet? MNRASL 499 (1): L111-L115; doi: 10.1093/mnrasl/slaa161
