SETI observatories conducted multi-hour radio scans of comet 3I/ATLAS, ruling out technological markers and setting limits on potential signals amid growing interest in interstellar objects.
Astronomers found no indications of artificial activity from the interstellar object 3I/ATLAS – the third known object to enter our solar system from interstellar space. This conclusion was reached by an international research team from the SETI Institute (Search for Extraterrestrial Intelligence) after analyzing the object’s radio signals using the Allen Telescope Array in California.
Comet 3I/ATLAS was first detected on July 1, 2025, by the ATLAS system (Asteroid Terrestrial-impact Last Alert System). It became the third confirmed interstellar object, following 1I/’Oumuamua (2017) and comet 2I/Borisov (2019). Unlike the first object, which sparked debate due to its unusual shape and trajectory, 3I/ATLAS quickly exhibited cometary characteristics, developing a tail and emitting gas and dust as it approached the Sun.
Despite the object’s cometary nature, the SETI team performed a standard search for technological markers – signs of potential artificial activity. The study, published in The Astronomical Journal, involved specialists from the SETI Institute, the Breakthrough Listen project, the Berkeley SETI Research Center, as well as the Jodrell Bank Centre for Astrophysics and several universities.
Observations were carried out for over 7 hours within the radio frequency range of 1 to 9 GHz. This range is suitable for detecting narrow-band signals, which are extremely rare in nature and could be considered potential indicators of technological sources.
During the analysis, the system recorded approximately 74 million narrow-band signals. However, the vast majority were attributed to radio frequency interference. After filtering, researchers identified 211 candidate signals that passed visual inspection in the time-frequency domain. None of these were deemed artificial.
The authors note that the absence of a signal was an expected outcome given the object’s nature. Nevertheless, the experiment itself is significant as a methodological test of modern radio astronomy’s capabilities. The team also established upper limits for the power of a potential transmitter near 3I/ATLAS, indicating that signals stronger than approximately 10^10 watts in the surveyed range would have been detected.
According to Sofia Sheikh, one of the study’s authors, “Observations like these are crucial for establishing a baseline of natural interstellar objects. This allows us to distinguish rare anomalies from natural processes in the future.” The researchers also emphasize that one day, spacecraft like Voyager will themselves become interstellar objects and potential “technological markers” in other systems.
Scientists point out that studying interstellar objects is important not only for the search for extraterrestrial technology but also for understanding the composition of other planetary systems and the processes occurring in the interstellar medium. Each new object of this type serves as a natural laboratory for testing models of planetary system formation and evolution.
Thus, while 3I/ATLAS showed no signs of artificial origin, the observations confirmed the ability of modern radio instruments to respond promptly to the appearance of interstellar objects and conduct sensitive searches for potential techno-signatures across a broad frequency range.
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