The interstellar comet 3I/ATLAS has been the subject of a flurry of sensational reports claiming that it is an alien spacecraft. However, recent studies show that no technosignatures, i.e., radio signals or emissions of substances indicating that extraterrestrial technology is operating on its surface, have been detected.

Comet 3I/ATLAS turned out not to be an alien spacecraft after all.
Source: starwalk.space

New observations

Since the interstellar object (ISO) 3I/ATLAS was first discovered on July 1, 2025, it has garnered much attention, including speculation, hopes, and fears that it may somehow contain evidence of technologically advanced civilizations outside of our solar system.

Now, a new paper published on the arXiv preprint server details the findings from radio observations made at the 100-meter Green Bank Telescope as a part of the Breakthrough Listen program, designed to look for signs of alien life. The data were taken on December 18, 2025 — the day before the object’s closest approach to Earth, and those hoping for evidence of advanced alien civilizations may not like the results.

3I/ATLAS — natural or artificial object?

Only two other ISOs have ever been observed to enter our solar system. The first ISO, 1I/Oumuamua, was initially classified as an asteroid, then a comet; while the second, 2I/Borisov, was deemed to be a comet. 3I/ATLAS exhibits typical cometary characteristics, like a coma and an unelongated nucleus.

Yet, these objects often initially spark a lot of speculation. After its discovery, many rumors spread online about odd features of 3I/ATLAS indicating alien technology. However, scientists have also been actively studying the object, albeit with a bit more skepticism.

Now that six months have passed since its discovery, multiple telescopes have taken data in various wavelength bands, including radio, infrared, X-ray, and optical, and these data have been analyzed by many researchers. According to SETI, none of these observations have resulted in evidence of technosignatures.

Green Bank observations

The researchers involved in the new study say that interstellar probes are most likely to communicate using narrowband radio signals, due to their transmission efficiency and because of the low extinction associated with these signals across interstellar space. And so, the team conducted their signal search at four different radio bands covering 1-12 GHz right around the time of the comet’s closest approach.

The search picked up over 471,000 candidate signals initially, but after applying a sky localization filter, they were left with nine “events.” Further analysis showed that these were due to radio frequency interference, as they also appeared in off-target scans or were known contaminants. Even with its higher levels of sensitivity, the analysis found no candidate technosignature signals from 3I/ATLAS, which is in line with the results of other studies.

The study authors write, “Our survey concludes that there are no isotropic continuous-wave transmitters above 0.1W at the location of 3I/ATLAS. For comparison, a cell phone is an approximately isotropic continuous-wave transmitter at a level of ∼1W.”

The search continues

The data used in this study and other studies from the Breakthrough Listen program are publicly available, and data collection will continue on certain telescopes, such as Hubble. Those interested in 3I/ATLAS can expect more information to come, although it is unlikely at this point that technosignatures will be found.

Still, Earth’s many telescopes will continue to be on the lookout for future ISOs entering our solar system and potential technosignatures.