A search for aliens communicating between planets in one of the most promising systems to look for life has come up empty.
Discovered in 2017, TRAPPIST-1 is a system of seven Earth-sized planets orbiting a red dwarf star much dimmer than our sun, about 40 light years away. The planets all orbit closer than Mercury does to our sun and pass in front of their star from our point of view. Three of the planets orbit in the star’s habitable zone, where liquid water can exist, and they might be good locations to look for life.
Their tight orbits mean these planets often cross over each other as well when we look at the system. at the Pennsylvania State University and his colleagues used this knowledge to look for radio signals that might leak in our direction when two of the planets talked to each other, supposing any intelligent alien civilisations were present.
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They observed seven events in 2022, lasting 6 hours in total, using the Allen Telescope Array in California that might have resulted in such a leakage. “Ultimately we didn’t detect any signals,” says Tusay.
The team’s search would have been sensitive to a radio signal at least as powerful as those transmitted by the Arecibo Observatory in Puerto Rico, which was once the world’s largest radio telescope before it collapsed in 2020. However, it is possible aliens could have been communicating using weaker instruments, or at times when the team wasn’t looking, meaning interplanetary communications in the TRAPPIST-1 system cannot be completely ruled out. “Maybe we just didn’t observe at the right time,” says Tusay.
Tusay says there are 60 to 70 other systems in our vicinity that could also be good targets for similar searches, but none quite as promising as this. “TRAPPIST-1 is just so good,” he says. “Seven planets that are nearly perfectly aligned is very rare.”
arXiv
