Search for extraterrestrial signals sent between exoplanets

There are thousands of signals coming from space that could be of extraterrestrial and intelligent origin. The researchers consider the hypothesis of an exchange of communications between civilizations on the various TRAPPIST-1 exoplanets.

Searching for extraterrestrial signals sent between exoplanets
Scientists at the Research Institute for Extraterrestrial Intelligence (SETI) and Penn State statedon October 16, 2024, who used radio telescopes to search for signs of extraterrestrial 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 close, about 40.66 light-years from Earth. To date, scientists have not found any signs of signals.
The team used the Allen Telescope Array, a set of radio telescopes dedicated to SETI located in California.

This research shows that we are getting closer to detecting radio signals similar to those we send into space.
Most research assumes some intent, like headlights, because our receivers have a sensitivity limit to a minimum transmit power beyond anything we unintentionally send. But with better equipment, like the future Square Kilometer Array (WILL), we may soon be able to detect signals from an alien civilization communicating with your spacecraft.

Said Nick Tusay, a graduate student at Penn State.
Radio signals between TRAPPIST-1 planets
Scientists believe that if there are intelligent aliens living among the seven TRAPPIST-1 planets, then we may be able to pick up radio signals sent between the planets.
The idea is not just that the inhabitants of one planet are talking to another. But as with Mars rovers and scientists on Earth, other civilizations could also be exploring nearby worlds and sending communications to their spacecraft.
The team analyzed a wide range of frequencies. But they were looking for signals that occupied only a narrow band of these frequencies. It would be like tuning the dial on the radio until you find a broadcast on a specific channel.
Although the team found millions of potential signals, they had to narrow them down to the most likely candidates. They ended up finding 11,000, which they gave further analysis.
From these, they further reduced the list to signals that occurred during planet-to-planet occultations. (A planet-planet occultation occurs when a planet passes in front of another planet.)
If an extraterrestrial civilization is sending a message to another planet that is directly in our path, those messages could leak to Earth. Thus, the signals that arrived during the planet-to-planet occultations left us with 2,264 signals.

Let's imagine we are looking at this distant star and two of its planets. When the Saturn-shaped planet sends a message to the smaller green planet, some of those radio waves can escape and reach Earth. Image via Zayna Sheikh/SETI.

Human signals coming from Earth
One of the complications of this type of research is that, even when radio astronomers point their telescopes into space, they continue to capture terrestrial signals. And the situation is getting worse due to the increasing number of spacecraft in Earth's orbit.
Thus, all the intriguing signals the project detected came not from TRAPPIST-1, but from human sources. But with the telescope upgrade and more practice identifying human sources, the team believes they are closer to finding a non-human signal.

This project included the work of undergraduate students in the 2023 SETI Institute Research Experience for Undergraduates (REU) program. The students looked for signs of human orbits around Mars to see if the system could detect signals correctly. It was an exciting way to engage students in cutting-edge SETI research.

Said Sofia Sheikh, from the Institute SETI.

Therefore, scientists will continue to improve their techniques and explore new systems. Additionally, they plan to use even larger telescopes that can capture weaker signals.
Conclusion: Scientists looked for alien signals sent between exoplanets in the TRAPPIST-1 system. They used radio telescopes to look for intelligent transmissions.