Since its discovery in July 2025 by the ATLAS system in Chile, 3I/ATLAS has been viewed with skepticism, fascination and alarm. Its trajectory confirms that it is an interstellar object: it entered the solar system with a hyperbolic orbit, which implies that it is not linked to the Sun and that it will rise again into deep space.
But what has decided to revive the debate is not only its origin, but its strange behaviors. In addition to showing an acceleration that cannot be explained by gravity alone (“non-gravitational acceleration”), some astronomers, including Avi Loeb, have pointed out that Its inner brightness (the luminosity of its coma and nucleus) reveals an unusual pattern, what they have dubbed the controlled emission pattern.
The expression refers to the distribution of light around the comet: instead of a diffuse, chaotic and irregular coma, typical of comets that sublime ice and expel gas and dust freely, 3I/ATLAS would show a concentrated and stable luminosity, with a compact “central coma” and a very uniform brightness. This uniformity is more reminiscent of a continuously energized source, such as a structured emission, than the normal chaotic effect of gases and dust being released randomly.
In simple words: if ordinary comets “burp” into space in the form of clouds, jets and messy drips, 3I/ATLAS would appear to emit light (or energy) with regularity, symmetry and predictabilityas if something controlled it, hence the controlled pattern characteristics.
The other anomaly is its trajectory: after passing close to the Sun, an additional acceleration not explained only by gravity was detected, which altered its course. This non-gravitational acceleration could come from the ejection of gas typical of comets, but there are doubts: Calculations show that to generate that sublimation boost, 3I/ATLAS would have to lose an enormous amount of mass.
For Loeb, if a large gas/dust cloud does not appear after perihelion (which many recent observations have not confirmed) then the natural mechanism (sublimation) is unlikely, opening the door to more speculative interpretations, such as that some form of anomalous propulsion is driving it.
By combining both facts (a stable light emission and an unexplained acceleration) the hypothesis of an “atypical natural object” is no longer the only one on the table. According to Loeb, The data requires keeping all possibilities open: “an engine cannot be ruled out yet.”
The majority of the astronomical community maintains that 3I/ATLAS is most likely a natural comet. A recent study suggests that the observed acceleration can be explained by anisotropic ejection (localized jets of CO/CO₂ gas) under reasonable physical conditions. This model predicts that, with a small fraction of active area in its core, it would be possible to reproduce both the magnitude and the direction of the acceleration without invoking exotic mechanisms.
For the authors of this latest study, the luminosity images (the aforementioned controlled emission pattern) could be due to specific coma geometries, comet orientation, size and type of ejected particlesand effects of solar radiation, without the need for internal machinery.
3I/ATLAS has opened a rare window into the limits of what we know. If it turns out to be a natural comet, it will expand what we know about how interstellar objects operate under extreme conditions. If, instead, evidence of an unnatural mechanism is found, it could reignite one of the most provocative debates in modern astronomy: have we detected an interstellar probe? Extraordinary claims require extraordinary evidence.