Harvard astrophysicist Avi Loeb has sparked significant debate in the scientific community with his assertion that the interstellar object 3I/ATLAS could potentially be artificial. This hypothesis arises from the unusual characteristics of the object, which resembles a comet but does not exhibit the typical gas cloud expected from such celestial bodies. If 3I/ATLAS fails to display detectable outgassing, Loeb argues, it challenges conventional natural explanations and raises the possibility of encountering alien technology.
Discovered by the ATLAS survey team in Rio Hurtado, Chile, on July 1, 2025, 3I/ATLAS is the third confirmed interstellar object to pass through our solar system. Unlike classical comets, which orbit the Sun, this object originates from beyond the heliosphere, suggesting it was expelled from a different star system billions of years ago. Its hyperbolic trajectory indicates that it has the velocity necessary to escape our Sun’s gravitational pull, reaching speeds up to 244,600 km/h.
Unusual Characteristics of 3I/ATLAS
The dimensions of 3I/ATLAS are also noteworthy, with estimates indicating its central nucleus measures between 0.44 km and 5.6 km across, translating to a mass of at least 33 billion tons if solid. This makes it significantly larger than the previous interstellar comet, 2I/Borisov. 3I/ATLAS’s closest approach to the Sun, termed perihelion, occurred on October 29, 2025, at a distance of approximately 1.36 AU. This point marked a critical moment when solar heat intensified, leading to unexpected behaviors observed in the object.
Loeb noted, “The surface area required to account for the mass flow in the large-scale jets — extending out to a million kilometres towards the Sun — is untenable. Given the solar power per unit area, the jets require an object larger than Manhattan Island.” He further observed that the latest imaging from the Nordic Optical Telescope did not indicate fragmentation, which could otherwise provide the large surface area needed for such jets.
One of the most intriguing aspects of 3I/ATLAS is its non-gravitational acceleration, first highlighted by Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory. Recent observations using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed a 4 arcsecond deviation in its path from what gravitational forces would predict. This acceleration, measured over 50 days, equates to a force of 0.02 mm/s² and a velocity change of 86 m/s.
Challenging Conventional Theories
In typical comets, such non-gravitational movement results from the “rocket effect,” where sublimating ice releases gas unevenly. However, recent studies, including data from the International Asteroid Warning Network (IAWN), suggest that 3I/ATLAS’s acceleration would require the loss of between 13% and 16% of its total mass to explain its trajectory. Yet, initial observations after perihelion showed no substantial visible coma or tail, raising further questions about its outgassing efficiency.
The object has also exhibited a striking color shift, changing from reddish to deep blue as it approached the Sun. This alteration may indicate ionized carbon monoxide emissions rather than typical dust scattering. Just prior to perihelion, the comet’s brightness surged, suggesting a rapid ejection of material.
Moreover, the presence of an “anti-tail” directed towards the Sun has been observed, a phenomenon usually attributed to the size distribution of dust particles released by the comet. Despite these explanations, 3I/ATLAS continues to present anomalies that challenge standard models of comet behavior.
Loeb has identified a series of peculiarities surrounding 3I/ATLAS, including its orbit near the solar system’s ecliptic plane and the timing of its closest approach while hidden behind the Sun. These characteristics are rarely seen in computer simulations of comet behavior.
While some scientists argue for a natural explanation, attributing the object’s unusual properties to the effects of cosmic radiation and environmental factors from its original star system, the debate is intensifying. The upcoming observations planned for December 2025 will be crucial. If no gas cloud is detected, Loeb’s argument for artificial propulsion might gain further traction.
In conclusion, while the acceleration of 3I/ATLAS initially puzzled scientists, ongoing research suggests a complex interplay of natural phenomena rather than a straightforward explanation. The findings underscore the necessity of interdisciplinary collaboration in astronomy, merging empirical observations with innovative theoretical frameworks. As astronomers continue to study this enigmatic object, its implications for our understanding of interstellar bodies and the potential for alien technology remain compelling and unresolved.
