Here's Why Harvard Scientist Avi Loeb Claims 40% Chance 3I/ATLAS Is Alien Technology

Imagine a piece of rock and ice, forged in the violent crucible of a star system millions of years ago, finally arriving on your doorstep. Since July 2025, that is exactly what the global scientific community has been grappling with: the arrival of a new, unexpected visitor from outside our Solar System, the interstellar comet 3I/ATLAS.

Confirmed as only the third object of its kind to pass through our cosmic neighbourhood, its mere existence is a precious scientific opportunity, but it has quickly become a focal point of intense controversy.

The object was detected by the ATLAS telescope system in Chile, moving at an astonishing 58 km/s in relation to the Sun. This excessive velocity is key evidence of its birth in a distant star system, offering an unprecedented opportunity to analyse materials formed in an alien planetary environment.

Yet, while astronomers rush to collect data on its chemical composition, the discovery has reignited the intense and passionate debate about the possibility of extraterrestrial technology. Peculiar anomalies observed on the comet refuse to fit neatly into established cometary models, fuelling a high-stakes scientific discussion that is rapidly gaining traction both in academic circles and across social media.

The Hyperbolic Trajectory: Where is 3I/ATLAS Going?

The journey of 3I/ATLAS through the Solar System is defined by a mathematical path known as a hyperbolic orbit. This path is crucial because it confirms the object possesses sufficient kinetic energy to completely escape the gravitational pull of the Sun. This is fundamentally a one-time visit; after crossing our region, it will continue its journey back to deep space, never to return.

Analysis of its trajectory suggests a profound origin, indicating that it approached from the direction of the constellation Sagitário, implying a voyage lasting millions, or perhaps billions, of years through the silent, interstellar vacuum. The comet reached its closest approach to the Sun, or perihelion, on October 29, 2025, at a distance of 1.36 astronomical units, which is equivalent to approximately 203 million kilometres.

Detailed observations by the James Webb Space Telescope have provided the first invaluable glimpses into the comet's composition. Spectral analysis revealed an abundance of carbon dioxide, alongside the presence of water ice and carbon monoxide.

This combination differs subtly from the mix found in comets native to our Solar System, such as those originating in the Oort Cloud, pointing to a formation environment in a potentially older star system and subject to different radiation levels. The object displays clear cometary activity, including a coma, the cloud of gas and dust surrounding the nucleus, which measures about 3 arcseconds.

Crucially, the object's speed showed non-gravitational accelerations, which are typically attributed to the ejection of gases from the icy core. Further analysis found that the core releases cyanide and nickel vapour, elements also commonly seen in solar comets.

Anomalous Features: The Case for a Technological 3I/ATLAS

The most explosive element of the comet's narrative centres on the publication of a July 2025 analysis led by Avi Loeb, a renowned astronomer from Harvard University. Professor Loeb and his team argued that a specific set of eight anomalous features—including peculiarly behaving gas jets and an orbital alignment considered highly unlikely for a purely natural object—could be better explained if 3I/ATLAS were, in fact, a technological artefact.

Key among these features is a measured density that suggests the comet is structurally hollow, far less dense than a typical rubble pile, which would grant it significantly more leverage against solar radiation pressure. Furthermore, its orbital alignment places it nearly perfectly in the plane of the Milky Way galaxy, an orientation considered statistically improbable for a randomly ejected object.

This bold hypothesis, which the author himself estimates to have a 40% probability, based on a probabilistic calculation that assigns a high degree of improbability to the combination of observed properties—especially the unexpected level of non-gravitational acceleration—if the object were solely composed of water ice and rock, is based primarily on accelerations that do not seem to be fully justified by the sublimation of ice, the usual cometary phenomenon.For 3I/ATLAS, the non-gravitational force acts strongly, but the lack of an accompanying large gaseous coma implies the source of acceleration is not simply volatile sublimation, but potentially solar radiation pressure acting on a structure with an extremely large surface area to mass ratio, characteristic of a light sail or thin shell.

This line of reasoning echoes the fierce debate generated by the first interstellar visitor, 1I/ʻOumuamua, in 2017, which also presented anomalous acceleration and a shape that defied conventional explanations. The controversy led Professor Loeb to accept a thousand-dollar bet against sceptical scientists, predicting that data collected by 2030 will definitively confirm or rule out his controversial theory'.

A Unified Front: Global Observational Effort on 3I/ATLAS

International space agencies and observatories have mobilised swiftly to observe the object. The Very Large Telescope (VLT), located in Chile, was one of the first facilities to confirm the cometary nature of 3I/ATLAS, successfully capturing cyanide gas emissions in August 2025. The European Space Agency (ESA) also played a crucial role, using data from the ExoMars Trace Gas Orbiter in October to refine the object's trajectory, reducing the uncertainties of its orbit tenfold.

Furthermore, several NASA missions, such as Psyche and Lucy, were temporarily redirected in September 2025 to record images, providing invaluable data about the comet's ion tail and hydrogen coma. This intensive monitoring quickly yielded results: high-resolution images indicate the occurrence of cryovolcano eruptions on the surface of the comet's nucleus. This phenomenon, where solar heat causes volatile ices to sublime and erupt into jets of gas, directly explains the sudden increases in brightness observed before its closest approach to the Sun.

The Place of 3I/ATLAS Among Interstellar Visitors

The passage of 3I/ATLAS provides a vital data point for direct comparison with its two predecessors. 1I/ʻOumuamua (2017) intrigued scientists for its extremely elongated shape and lack of a visible coma despite its non-gravitational acceleration, which initially fuelled Professor Loeb's theories about alien technology. Conversely, 2I/Borisov (2019) behaved in a much more familiar way, displaying a clear coma and tail and a chemical composition very similar to that of our Solar System comets. 3I/ATLAS sits between the two, showing clear cometary activity but with a chemical composition and non-gravitational behaviour that distinguish it.

Astronomers will continue to monitor 3I/ATLAS as it moves away, crossing the constellations of Virgem and Leão in December 2025. Due to its apparent magnitude, which is below 12, the comet remains invisible to the naked eye, requiring telescopes for observation. The comet's passage reinforces the importance of monitoring networks such as the ATLAS system, which are part of NASA's planetary defence, designed to detect objects close to Earth. While the public debate reflects an enduring fascination with the cosmos and the question of extraterrestrial life, the official position of agencies such as NASA, issued in November 2025, is clear: 3I/ATLAS is a natural comet, and there is no evidence to suggest an artificial origin or any type of threat'.

As 3I/ATLAS accelerates back toward the cosmic dark, it leaves behind an unprecedented set of data—and a raging scientific debate that pits conventional cometary models against the provocative possibility of an alien artefact. While NASA maintains a clear position that the object is natural, the case for its anomalous features remains open.