Searching for alien signals sent between exoplanets
Scientists from the Search for Extraterrestrial Intelligence Institute (SETI) and Penn State said on October 16, 2024, that they’ve used radio telescopes to search for signs of alien communications between the seven exoplanets in the TRAPPIST-1 system. The TRAPPIST-1 system is home to a red dwarf star, and some of its seven exoplanets are in the habitable zone, where life could exist. The TRAPPIST-1 system is relatively nearby, at about 40.66 light-years from Earth. So far, the scientists have not found any evidence for signals.
The team used the Allen Telescope Array, a dedicated SETI array of radio telescopes located in California. The scientists logged 28 hours scanning the system for alien signals, which is:
the longest single-target search for radio signals from TRAPPIST-1.
Graduate student Nick Tusay of Penn State said:
This research shows we are getting closer to detecting radio signals similar to the ones we send into space. Most searches assume some intent, like beacons, because our receivers have a sensitivity limit to a minimum transmitter power beyond anything we unintentionally send out. But, with better equipment, like the upcoming Square Kilometer Array (SKA), we might soon be able to detect signals from an alien civilization communicating with its spacecraft.
The Astronomical Journal has accepted the team’s study for publication. A pre-print is available on arXiv.
Radio signals between TRAPPIST-1 planets
The scientists believe that if there are intelligent aliens living among the seven TRAPPIST-1 planets, then we might be able to catch radio signals sent between the planets. The idea is not just that inhabitants of one planet are talking to another. But, just as the case with Mars rovers and scientists on Earth, other civilizations could also be exploring nearby worlds and beaming communications to their spacecraft.
The team analyzed a wide range of frequencies. But they were looking for signals that only occupy a narrow range of those frequencies. It would be like tuning the dial across the radio until you hit a transmission on a specific channel.
While the team found millions of potential signals, they then had to narrow those down to the most likely candidates. They ended up with 11,000 that they then gave further scrutiny to. From those, they further narrowed it down to signals that occurred during planet-planet occultations. (A planet-planet occultation occurs when one planet passes in front of another planet.) If an alien civilization is beaming a message to another planet that is directly in the path with us, those messages could leak toward Earth. So, the signals that arrived during planet-planet occultations left them with 2,264 signals. But they said:
None of the signals were of non-human origin.
Human signals originating from Earth
One of the complications with this type of search, is that even when radio astronomers point their telescopes into space, they still pick up earthly signals. And the situation is getting worse due to the ever-accumulating amounts of spacecraft in Earth orbit.
So all the intriguing signals the project detected were not from TRAPPIST-1 but from human sources. But with telescope upgrades and more practice identifying human sources, the team believes they are getting closer to finding a non-human signal.
Sofia Sheikh of the SETI Institute said:
This project included work by undergraduate students in the 2023 SETI Institute Research Experience for Undergraduates (REU) program. The students looked for signals from human-made orbiters around Mars to check if the system could detect signals correctly. It was an exciting way to involve students in cutting-edge SETI research.
And so the scientists will continue to refine their techniques and explore new systems. Plus, they plan to use even larger telescopes that can pick up fainter signals.
Bottom line: Scientists looked for alien signals sent between exoplanets in the TRAPPIST-1 system. They used radio telescopes to seek the intelligent transmissions.
Source: A Radio Technosignature Search of TRAPPIST-1 with the Allen Telescope Array
Via SETI