The interstellar object known as 3I/ATLAS, first detected on July 1, 2025, has been identified as a source of intriguing yet ultimately mundane signals. Researchers initially speculated that the object might harbor signs of extraterrestrial technology, but further analysis revealed that nine radio signals attributed to it were, in fact, human-made noise.
3I/ATLAS, discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii, captured significant attention because it is the third recognized interstellar object to traverse our Solar System. Its unbound trajectory indicated that it originated beyond the Solar System, prompting discussions about its potential origins, including the possibility of it being a technological probe.
Signals Under Scrutiny
During its closest approach to Earth, approximately 270 million kilometres away, 3I/ATLAS remained within reach of powerful radio telescopes. The Breakthrough Listen initiative, which focuses on detecting signs of intelligent extraterrestrial communications, took this opportunity to conduct a comprehensive search for so-called technosignatures. The team utilized the Green Bank Telescope in West Virginia, examining radio frequencies between 1 and 12 gigahertz, including the ‘water hole’—a quiet section of the radio spectrum considered ideal for intelligent signals.
Simultaneously, the Allen Telescope Array in California and other collaborating observatories contributed to one of the most detailed searches for technosignatures ever performed on an interstellar object. The campaign initially detected nine radio events that warranted further investigation. Each signal appeared as a sharp spike in frequency, matching patterns typically associated with potential technosignatures.
However, upon closer examination, researchers discovered that these signals coincided with the telescope’s pointing at times when it was not aimed directly at 3I/ATLAS. This pattern suggested interference from human technology, such as satellites, aircraft transmitters, and terrestrial communication systems regularly contaminating astronomical observations.
In a preliminary paper awaiting peer review, the research team concluded: “Like those searches, we find no credible detections of narrowband radio technosignatures originating from 3I/ATLAS.” They noted that similar studies conducted in 2025 using different telescopes and frequency ranges yielded no evidence of extraterrestrial signals.
Cometary Characteristics Confirmed
While the technosignature search unfolded, another group of scientists focused on understanding the physical characteristics of 3I/ATLAS. They investigated its non-gravitational acceleration—an effect resulting from sunlight warming the comet, which causes gas jets to act like natural thrusters. By analyzing this data alongside estimates of material loss, they estimated that the nucleus of 3I/ATLAS measures roughly one kilometre across, typical of known Solar System comets.
The research team found no signs of unusual reflectivity or erratic motion that might suggest artificial origins. Their findings indicated that “3I/ATLAS exhibits mostly typical cometary characteristics.” They emphasized, “There is currently no evidence to suggest that interstellar objects (ISOs) are anything other than natural astrophysical phenomena.”
As 3I/ATLAS departs from the Solar System, it reinforces the idea that natural forces can create compelling cosmic phenomena without the influence of alien technology. The efforts made in studying this interstellar visitor highlight the dedication of astronomers to explore even the slightest possibility of detecting signs of other civilizations.
The nine radio signals, while not groundbreaking, served as a valuable exercise in refining detection methods for future interstellar objects. As 3I/ATLAS fades into the depths of space, it leaves behind a clearer understanding of what to look for in future surveys, underscoring the importance of ongoing support for initiatives like Breakthrough Listen. Protecting the radio spectrum from interference and fostering public interest in meticulous, data-driven astronomy will be essential for future investigations into the cosmos.
