O interstellar object 3I/ATLASThe object, discovered on July 1, 2025, was the subject of highly sensitive radio observations conducted on December 18, 2025 by the Green Bank Telescope as part of the Breakthrough Listen program, without finding evidence of technosignatures or artificial signals associated with the body.
Since its identification, 3I/ATLAS has attracted significant attention from researchers and the public, fueling speculation, expectations, and fears about the possibility that the object contains evidence of technologically advanced civilizations outside the solar system.
A new scientific article, published on the preprint server. arXivThis details the results of radio observations conducted one day before the object’s closest approach to Earth.
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The data analyzed are part of the systematic effort of the Breakthrough Listen program, aimed at searching for technological signals originating from outside Earth.
Despite the high sensitivity achieved in the measurements, the results presented do not indicate the presence of artificial transmissions associated with 3I/ATLAS, contradicting the expectations of some in the community interested in evidence of intelligent extraterrestrial life.
Interstellar object and context of initial speculations
To date, only three interstellar objects have been observed traversing the solar system. The first, 1I/Oumuamua, was initially classified as an asteroid and later as a comet. The second, 2I/Borisov, was directly identified as a comet.
The 3I/ATLAS, in turn, presents typical characteristics of this type of body, including the presence of a coma and a nucleus that is not elongated.
Even so, as with other objects of this type, its discovery was followed by a wave of speculation. After the official announcement, rumors spread on social media about supposed anomalous characteristics of 3I/ATLAS, suggesting a possible artificial origin.
Meanwhile, scientific teams began detailed studies of the object, adopting a more cautious approach based on observational evidence.
The study’s authors themselves emphasize that, to date, there is no evidence to suggest that interstellar objects are anything more than natural astrophysical bodies. Even so, they stress that the extremely limited number of known ISOs justifies in-depth investigations, given that interstellar probes are considered a plausible form of technosignature.
NASA’s James Webb Space Telescope observed interstellar comet 3I/ATLAS on August 6 with its Near-Infrared Spectrograph instrument. Credit: NASA
Methodology of radio observations in Green Bank
The observations described in the new article were made with the Green Bank 100-meter radio telescope, one of the most sensitive instruments in the world for this type of study.
The researchers focused their search on narrowband radio signals, which are considered more efficient for interstellar communication and less susceptible to attenuation in space.
The team conducted the analysis in four different radio bands, covering frequencies between 1 and 12 GHz, approximately during the period of 3I/ATLAS’s closest approach to Earth. This range was chosen to maximize the possibility of detecting any artificial transmissions associated with the object.
Initially, the search identified over 471.000 candidate signals. After applying filters that take into account the location in the sky, this number was reduced to just nine events.
Further analysis demonstrated that all of these signals were consistent with radio frequency interference, as they also appeared in off-target observations or corresponded to known contaminants.
Results and limitations of the sensitivity achieved.
Even operating at its highest sensitivity levels, the study did not find any candidate signal that could be attributed to a technosignature originating from 3I/ATLAS.
This result is consistent with analyses conducted by other research groups that also observed the object in different ranges of the electromagnetic spectrum.
The authors state that the research allows them to conclude that there are no isotropic continuous wave transmitters above 0,1 W at the 3I/ATLAS location.
For comparison purposes, the study notes that a typical cell phone functions as a nearly isotropic continuous wave transmitter at a level close to 1 W.
The distribution of the analyzed signals, including the relationship between frequency, drift rate, and signal-to-noise ratio, was detailed in the article. None of the detected events coincided with the drift rate regions expected from the Earth’s orbital and rotational motion or the rotation of 3I/ATLAS itself, reinforcing the negative conclusion regarding the presence of artificial signals.
Ongoing analysis and future monitoring.
Six months after the object’s discovery, data from 3I/ATLAS has already been collected across various wavelength ranges, including radioinfrared, X-rays and optical.
These observations have been analyzed by multiple research groups, but no evidence of technosignatures has been identified so far, according to information from SETI.
The data used in the study, as well as in other research from the Breakthrough Listen program, are publicly available. The collection of new observations will continue at several telescopes, including Hubble, allowing for further analysis as the object moves away.
Although the authors themselves believe that future observations are unlikely to reveal technological signals associated with 3I/ATLAS, the researchers emphasize that surveillance will continue.
The numerous ground-based telescopes will remain vigilant for the entry of new interstellar objects into the solar system and the eventual detection of technological signatures, maintaining active monitoring in the face of each new ISO that is identified, even if the current results reinforce the natural nature of these bodies.
This article was produced based on data and analyses published in arXiv, in the Breakthrough Listen program and in information released by SETI.