Just 40 light-years from Earth, a red dwarf star named TRAPPIST-1 intrigues astronomers with its exceptional planetary system. Orbiting it are seven rocky planets similar in size to our own, several of which could harbor liquid water—a key ingredient for life as we know it. This unique configuration makes it an ideal laboratory for tracking potential extraterrestrial civilizations.
A team of Chinese researchers mobilized the FAST radio telescope, the world's largest and most sensitive, to observe TRAPPIST-1 for nearly two hours. They analyzed specific radio frequencies capable of revealing artificial emissions, with unprecedented resolution allowing the detection of extremely weak signals. This targeted approach aimed to identify coherent transmissions, impossible to produce naturally, which would have indicated the presence of advanced technology.
Despite the remarkable sensitivity of the radio telescope, no convincing evidence of technological activity was identified. This negative result is not an end in itself: it helps establish upper limits on the power of potential transmitters in this system.
Scientists are not giving up, however. They plan to expand their research to other types of signals, such as periodic or transient emissions, which might escape current methods. TRAPPIST-1 remains a priority target.
Red dwarfs and their habitable potential
Red dwarfs are the most common stars in the Universe, characterized by their low mass and long lifespan, which can reach several times the current age of the Universe. Simply put: they have such longevity that no red dwarf has yet reached the end of its life. Their relative stability offers a potentially favorable environment for the development of life over immense timescales.
However, these stars often emit violent flares (bursts of radiation) and intense ultraviolet radiation, which could sterilize nearby planets. For a planet to be habitable, it must possess a protective atmosphere or a sufficient magnetic field to mitigate these harmful effects.
Size comparison between TRAPPIST-1 and the Sun, illustrating the compact nature of this promising planetary system.
Credit: CactiStaccingCrane
Despite this, the proximity of red dwarfs with planets in their habitable zone facilitates their detection and study. Future missions, such as those of the James Webb Space Telescope, could analyze their atmospheres in search of biosignatures, such as oxygen or methane.
TRAPPIST-1 is an emblematic example, showing that even around modest stars, planetary diversity can rival that of our Solar System.
SETI research and its evolving methods
The search for extraterrestrial intelligence (SETI) primarily uses radio waves to detect artificial signals, based on the idea that advanced civilizations might emit transmissions detectable over great distances. Technological advances, such as the FAST radio telescope, have significantly increased the sensitivity of these searches.
Beyond continuous radio signals, scientists are now exploring other types of emissions, such as optical lasers or neutrinos, which could be markers of even more advanced technologies. Each method complements the others, covering a broader spectrum of possibilities.
The absence of detection to date does not invalidate the SETI effort; rather, it allows for the elimination of certain hypotheses and the refinement of future strategies. Citizen initiatives, such as the SETI@home project, even mobilize the public to analyze data, democratizing this quest.
In the long term, the combination of multi-messenger astronomy (gravitational waves, particles, etc.) could revolutionize our approach, offering unprecedented perspectives for unraveling the mystery of our solitude—or lack thereof—in the cosmos.