On July 1, 2025, the Asteroid Terrestrial-impact Last Alert System (ATLAS) detected 3I/ATLAS, the third interstellar object (ISO) observed passing through our Solar System since 2017. A team led by Technosignature Research Scientist Sofia Sheikh at the SETI Institute conducted a comprehensive radio survey of the object to search for potential artificial technosignatures, ultimately finding no evidence of extraterrestrial technology.
How Scientists Hunt for Interstellar Technology
Researchers used the Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California to scan 3I/ATLAS. According to the study published in The Astronomical Journal, the team monitored radio frequencies between 1 and 9 gigahertz (GHz) for over 7 hours. This broad frequency range is designed to detect narrowband signals that do not occur naturally, serving as a potential indicator of artificial technology.
The process involved filtering out 74 million initial signals to remove radio-frequency interference (RFI). From this, researchers identified 211 signals of interest for visual inspection. None of these were confirmed as artificial. “The results from 3I/ATLAS show how realistic it is to detect a signal with the technology we have today,” said co-author Valeria Garcia Lopez, a physics professor at Furman University and member of Breakthrough Listen at UC Berkeley.
The ATA team began observations less than 24 hours after the initial detection of 3I/ATLAS. This rapid response capability is essential for studying transient interstellar visitors before they move beyond the reach of Earth’s telescopes.
Why Interstellar Objects Matter for Future Research
Studying ISOs like 3I/ATLAS, 1I/’Oumuamua, and 2I/Borisov provides a rare look at materials from other star systems without the need for expensive space missions. Because these objects are essentially left over from the formation of planets, their composition offers clues about how other solar systems evolve. By establishing a baseline for natural interstellar objects, scientists can better identify potential anomalies that might indicate artificial origins.
As Dr. Sofia Sheikh noted in a SETI Institute release: “Eventually, our own Voyager spacecraft will be extraterrestrial artifacts in other stellar systems. Given that, it is important that we understand the natural distribution of interstellar objects so that we will be able to identify any anomalies that could one day be signs of an artificial interstellar object.”
Setting Limits on Extraterrestrial Signals
Even though the survey did not find a signal, it established critical scientific boundaries for future observations. The team successfully placed upper limits on the power of any transmitter potentially located on or near 3I/ATLAS. Specifically, the researchers ruled out signals stronger than approximately 10–110 watts across the observed frequency range. This data provides a reference point for future studies whenever another ISO enters our neighborhood.
Frequently Asked Questions
What is a technosignature?
A technosignature is any measurable property or effect that provides scientific evidence of past or present extraterrestrial technology.
Why search for signals from a comet?
While comets are natural, scientists search them for technosignatures to ensure that no artificial probes are hidden among natural interstellar visitors, given that humanity itself has sent probes like Voyager into interstellar space.
How many interstellar objects have been detected?
As of July 2025, astronomers have witnessed three interstellar objects in the last eight years: 1I/’Oumuamua (2017), 2I/Borisov (2019), and 3I/ATLAS (2025).
Where can I read the full study?
The findings regarding the search for radio technosignatures from 3I/ATLAS were detailed in a paper published in The Astronomical Journal.
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