Breakthrough Listen focused technosignature searches on 3I/ATLAS as it neared Earth

Interstellar comet 3I/ATLAS made its closest flyby past Earth on December 19, 2025. During that time, the Breakthrough Listen project searched for signs of technology or artificial intervention in the interstellar visitor.

While they worked on the search for technology, another team studied the non-gravitational acceleration of the object. Their primary motive was to analyze the size of the comet. 

Interstellar 3I/ATLAS was first reported on July 1, 2025, and has remained a topic of debate, with many, like Harvard astrophysicist Avi Loeb, insisting on the exploration of a potential technological side of the comet. 

However, since the comet’s safe flyby past Earth at a distance of 270 million kilometers, the claims of an alien origin have shifted significantly. 

Regardless, when the interstellar visitor flew past the planet, the Breakthrough Listen project seized the opportunity to analyze the comet for technosignatures, which could lead to significant discoveries. 

Breakthrough Listen is an astronomy project that looks into intelligent extraterrestrial communications. 

More details on the observations of Breakthrough Listen as they studied 3I/ATLAS during its closest approach to Earth

In their recent paper, which is yet to be peer reviewed, the team at Breakthrough Listen wrote that after observing 3I/ATLAS, they concluded:

“3I/ATLAS exhibits mostly typical cometary characteristics, including a coma and an elongated nucleus. There is currently no evidence to suggest that ISOs are anything other than natural astrophysical objects.”

However, they added that since the number of interstellar objects detected by humans is so low, it would be inappropriate to jump to conclusions. Thus, they suggested “a thorough study.”

“Putative nonanthropogenic interstellar probes are likely to communicate via narrowband radio signals for transmission efficiency and for the low extinction of such signals across interstellar space; all of humanity’s spacecraft, including the now-interstellar craft Voyager 1 and Voyager 2, communicate via such signals,” they continued.

For the moment, they deduced 3I/ATLAS to be a natural comet since there was not enough evidence to prove otherwise. 

SETI, or the Search for Extraterrestrial Intelligence Institute, released a statement shortly after the comet’s flyby, sharing that they used “the largest steerable single-dish radio telescope in the world” to check for alien behavior. 

Based on their studies, they discovered nine signals worth looking into. 

However, after close inspection, they concluded that all of those nine signals were only human-made radio noise and not anything unusual. 

According to them, signal frequencies show up more often when human-made radio noises interfere with them. While observing 3I/ATLAS, they noticed that the nine signal emerged when they were not looking at the target. 

Consequently, they deduced that they were human-made radio noise and nothing more. 

“Similar technosignature searches have recently been undertaken by S. Z. Sheikh et al. (2025) and D. J.  Pisano et al. (2025) over different frequency ranges and with different sensitivities. Like those searches, we find no credible detections of narrowband radio technosignatures originating from 3I/ATLAS,” the team said.

Another team studying the non-gravitational acceleration pointed out that when comets near the sun, they heat up. It melts their frozen materials, turning them into gas. Then, the uneven outgassing creates a small push, causing a non-gravitational acceleration. 

Based on that and the size of the nucleus, which they said is the typical size of other comets in the solar system, they conclude that 3I/ATLAS lost material as it heated up and showed nothing unusual. 

Stay tuned for more updates.