The interstellar comet 3I/ATLAS, the third confirmed object coming from outside Sistema Solar, passed close to Terra in December 2025 without showing evidence of artificial origin. Cientistas of the Breakthrough Listen project carried out dedicated observations to detect possible signs of extraterrestrial technology. The results indicated that no reliable signal was identified.
The discovery of 3I/ATLAS occurred on July 1, 2025 by the ATLAS system, designed to monitor asteroid threats. The object follows a hyperbolic trajectory, characteristic of bodies not gravitationally bound to Sol.
Discovery of the third interstellar visitor
Astronomers have identified 3I/ATLAS as the third confirmed interstellar comet in the history of observations. The ATLAS search system, operated in different locations, detected the object while carrying out routine scans of the sky. Confirmation of its external origin came from the analysis of its speed and trajectory.
The comet reached perihelion, the closest point to Sol, in October 2025, at approximately 1.4 astronomical units. Sua passage of Terra occurred on December 19, approximately 1.8 astronomical units away. Essa relative proximity allowed detailed observations using several instruments.
The 3I/ATLAS object is recognized as the third interstellar object in the history of observations.
—Jaime Maussan (@jaimemaussan1)July 9, 2025
Its diameter is around 10-30 km! And the movement speed is 61 km/s.
Could it be an artificial object?pic.twitter.com/7bgy21WEiI
Trajectory and observed characteristics
3I/ATLAS displayed a visible tail and nucleus, behaviors typical of natural comets. Telescópios and Gemini North recorded color changes and the development of gaseous structures as they approached Sol. Essas variations result from the sublimation of ice on the surface of the body.
X-ray observations carried out by the XMM-Newton space telescope of Agência Espacial Europeia captured emissions from the comet in December 2025. The data revealed interaction between the solar wind and materials released by the object. Essas characteristics reinforce the classification as a natural body composed of rocks and ice.
The Breakthrough Listen project and the search for signals
Breakthrough Listen represents an initiative dedicated to searching for extraterrestrial intelligence through radio signals. The program uses large telescopes to monitor celestial objects for narrow artificial emissions. In the case of 3I/ATLAS, the team prioritized observation during the close approach to Terra.
Another independent group carried out searches in different frequency bands, complementing the main efforts. Ambas campaigns followed established protocols to identify possible technosignatures, such as deliberate radio transmissions. The absence of detections in multiple analyzes increased confidence in the negative results.
Observation details on Green Bank Telescope
The Telescópio Green Bank, located in West Virginia, in the Estados Unidos, has a fully steerable 100 meter diameter antenna. Essa structure makes it the largest instrument of its kind in the world, ideal for sensitive radio searches. The 3I/ATLAS observation took place on December 18, 2025.
The researchers scanned four frequency bands while the comet was about 269 million kilometers from Terra. The system initially recorded hundreds of thousands of signal candidates. Further verification identified all as terrestrial interference or known sources.
History of known interstellar objects
Interstellar objects confirmed to date include three main cases. The first, 1I/’Oumuamua, was detected in 2017 and had an unusual elongated shape. The second, 2I/Borisov, identified in 2019, exhibited a coma and tail typical of comets.
- 1I/’Oumuamua: discovered in 2017, it accelerated in a non-gravitational way explained by the release of gases.
- 2I/Borisov: identified in 2019, first to show clear cometary activity.
- 3I/ATLAS: found in 2025, third confirmed with hyperbolic trajectory.
Similar searches for technosignatures on these previous objects also failed to detect artificial signals. Essas campaigns use the same telescopes and methods applied to 3I/ATLAS.
Reported anomalies and natural explanations
Some astronomers have pointed out variations in the brightness and non-gravitational acceleration of 3I/ATLAS as points of interest. Essas characteristics, however, receive explanations based on known physical processes in comets. The asymmetric release of gases can produce enough thrust to alter the trajectory.
Optical observations and observations at other wavelengths corroborate the object’s natural composition. The presence of anti-tail and color changes aligns with models of cometary evolution. The data accumulated from multiple instruments reinforces the interpretation as a primordial body of interstellar space.
Search campaign final results
Thorough analysis of the Green Bank data eliminated all early candidates for artificial signals. The remaining nine came from human sources in Terra, according to cross-referencing with known catalogues. The secondary campaign on other frequencies also returned negative results.
The researchers concluded that the probability of 3I/ATLAS being a technological artifact is extremely low based on the observations made. The object remains classified as a natural comet of interstellar origin. The data obtained contributes to the information bank on external visitors to Sistema Solar.
Importance of systematic searches
Carrying out searches for technosignatures on interstellar objects follows established scientific protocol. Cada close passage represents a unique opportunity for sensitive testing of hypotheses about intelligent life. The absence of detections does not eliminate possibilities, but it restricts specific scenarios.
The Green Bank Telescope maintains a central role in these initiatives due to its ability to detect weak signals at great distances. Projetos and Breakthrough Listen continue to monitor the sky for additional evidence. The 3I/ATLAS observations add valuable data to the global SETI exploration effort.
3I/ATLAS is now following its path out of Sistema Solar, with no prospect of return. Sua passage provided information about the composition and dynamics of bodies formed in other stellar systems. The records obtained remain available for future analysis by researchers.
