Astronomers are closely examining the interstellar object 3I/ATLAS, which was discovered in July 2025 by the ATLAS telescope in Chile. This object, estimated to measure between 20 and 40 kilometres, is currently travelling on a hyperbolic orbit at speeds exceeding 50 kilometres per second, confirming its extrasolar origin. Its detection marks the third known interstellar visitor, following 1I/’Oumuamua in 2017 and 2I/Borisov in 2019. However, what sets 3I/ATLAS apart is its unique behaviour: a jet emanating towards the Sun.
Scientists typically expect comets to exhibit tails that point away from the Sun due to solar radiation and solar wind. Yet observations of 3I/ATLAS have revealed a small jet directed sunward, with its nucleus located approximately 6,000 kilometres away. This anomaly has prompted notable scrutiny, particularly from Avi Loeb, a Harvard astrophysicist, who argues that the jet’s behaviour contradicts established cometary physics.
Loeb’s analysis indicates that if 3I/ATLAS were a standard comet, its antitail jet should not extend beyond 5,000 kilometres. The presence of a sunward jet has sparked controversy within the scientific community. Some researchers suggest that this behaviour may result from unusual outgassing patterns, potentially linked to the object’s composition. Others believe that the orientation and intensity of the jet may hint at previously unobserved processes in interstellar comets.
The observations of 3I/ATLAS have yielded eight significant anomalies, including its trajectory and spectral signatures. While Loeb has raised hypothetical scenarios regarding these findings, many mainstream astronomers advocate caution, emphasizing the need for further data before drawing conclusions.
Notable Observations and Data Collection
Images captured by the Two-Meter Twin Telescope in the Canary Islands during August 2025 revealed the striking purple jet extending toward the Sun. In these images, a yellow line indicated where a typical comet tail would be expected. Additional data from the European Space Agency’s XMM-Newton spacecraft showed the emission of low-energy X-rays when gases escaping from 3I/ATLAS interact with solar wind. These observations suggest that the object is actively outgassing, albeit in a manner that current models do not fully explain.
The anomalies associated with 3I/ATLAS underscore the challenges inherent in researching interstellar objects. Each visitor offers a rare opportunity to test hypotheses about planetary system formation and the behaviour of bodies in the cold reaches of outer space. Specifically, the sunward jet raises important questions regarding the composition and internal structure of 3I/ATLAS. If propelled by substances atypical of solar system comets, this could provide insights into the diversity of interstellar matter.
Alternatively, if the jet’s direction is influenced by rotational processes or other forces, this could enhance our understanding of cometary physics. Despite speculations regarding a non-natural origin, the prevailing scientific stance remains skeptical. Astronomers stress that unusual behaviour does not necessarily imply extraordinary explanations. Instead, they underscore the importance of gathering more data as 3I/ATLAS approaches perihelion and moves further from the solar system.
Loeb reiterates that, as a comet, the jet and antitail should not contain streaming gas beyond 5,000 kilometres. This statement highlights the necessity of comparing established models with new evidence rather than hastily reaching conclusions.
The case of 3I/ATLAS illustrates how interstellar visitors can challenge existing astronomical frameworks. Its sunward jet represents an apparent anomaly that could clarify its true nature, whether as a comet with distinctive characteristics or as an example of a broader category of interstellar objects awaiting further investigation. As the scientific community continues to observe and study this phenomenon, they recognize that each interstellar encounter presents a valuable opportunity to deepen our understanding of the universe.
