Scientists at the SETI Institute have completed a search for a possible technological signal coming from 3I/ATLAS, the third known interstellar object to transit our solar system. Researchers used the Allen Telescope Array (ATA) at Hat Creek Radio Astronomy Observatory in Northern California to scan a wide range of radio frequencies for evidence of extraterrestrial technology. As expected based on previous observations, they found no sign of an artificial signal, further supporting the conclusion that 3I/ATLAS is a natural comet-like object.
First seen in July 2025, 3I/ATLAS is the third confirmed interstellar object ever observed to enter the solar system. This follows the discoveries of 1I/’Oumuamua and 2I/Borisov, both of which occurred outside of our neighboring planet.
Because 3I/ATLAS formed around another star, it provides a rare opportunity for scientists to study material from another star system and gain insight into how planets and planetary systems develop. Although current evidence strongly points to a natural origin, researchers also see interstellar visitors as important targets in the search for technosignatures. In the unlikely event that any of these objects are man-made, it could reveal detectable technology and provide the first evidence of extraterrestrial life.
“Eventually, our own Voyager spacecraft will also become an extraterrestrial relic in another star system,” said Dr. Sophia Sheikh, lead author of the paper. “Given that, it is important to understand the natural distribution of interstellar objects so that we can one day identify anomalies that may be signs of artificial interstellar objects.”
To investigate that possibility, the team used ATA to observe 3I/ATLAS for over seven hours. The observations covered frequencies from 1 to 9 gigahertz, a range suitable for detecting narrowband radio transmissions. Such signals are not known to occur naturally and are considered evidence of technology.
Classify millions of signals
During the search, researchers detected approximately 74 million narrowband signals. It soon became clear that most of this was due to human interference.
After removing signals associated with Earth-based technology and narrowing the search to signals consistent with the movement of objects, only about 200 candidates remained. Further analysis revealed that all of these signals originate from technology on Earth or from satellites orbiting Earth.
No techno signatures detected
The investigation found no evidence of extraterrestrial technology. However, this result further supports the conclusion that 3I/ATLAS is a natural product.
This observation also establishes new limits on the strength of radio transmitters that may be on or near 3I/ATLAS. The study excluded transmissions exceeding approximately 10 to 110 watts, which is comparable to the power consumption of a typical household appliance, across the frequencies examined.
“The 3I/ATLAS results show how realistic it is to detect signals using the technology we have today,” said co-author Valeria García López. “That’s why it’s important to continue looking for technosignatures, even from objects where we don’t expect a signal.”
Rapid response to new interstellar discoveries
This study highlights the Allen Telescope Array’s ability to respond quickly when unusual objects are discovered. 3I/ATLAS observations began less than 24 hours after the discovery was announced, demonstrating how quickly the system can be deployed.
Beyond the search for intelligent life, observing interstellar visitors helps scientists better understand the physical characteristics of these objects as they pass through our solar system.
As astronomers continue to discover new interstellar objects, each object offers new opportunities to explore its technosignatures, expanding our knowledge of both natural and potentially technological phenomena beyond our solar system.
