The most sensational story of the year for astronomers was the discovery of comet 3I/ATLAS, which was first observed on July 1, 2025 by NASA’s Asteroid Earth Impact Warning System (ATLAS). Although comets regularly pass by Earth, the most famous being Halley’s Comet, there is something extra special about this new find. Halley’s and other well-known comets originated in our solar system, born from the same planet-forming disc from which the sun, Earth, and all the other planets emerged. What makes 3I/ATLAS so fascinating is that it originated somewhere beyond the solar system, and made its way here through interstellar space. As if that wasn’t an exciting enough discovery, a radio telescope noticed that the comet is emitting something.
The MeerKAT radio telescope in South Africa picked up on 3I/ATLAS in late October, as the comet was approaching its closest point to the sun. This finding was widely reported as radio signals emitting from 3I/ATLAS, leading conspiracy theorists to speculate that the object may actually be a piece of alien technology. This is not quite accurate though. Technically, everything emits electromagnetic radiation, and what MeerKAT found was not an audio transmission like the one we hear on a car radio. What she actually found were gaps in the radio spectrum caused by the absorption of radio waves by OH molecules, also known as hydroxyl radicals. OH molecules – the remnants of water torn by solar radiation – are regularly observed in comets that pass in the range of the Earth, which seems to put to rest any speculation that the 3I/ATLAS is something other than a comet. However, it does not answer the question of where 3I/ATLAS originated.
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Astronomers are still not sure where 3I/ATLAS came from
comet trajectory 3I/ATLAS – NASA/JPL-Caltech/University of Arizona
The 3I/ATLAS discovery marked only the third time astronomers have observed an interstellar object passing through our solar system. The “3I” in its name actually means “third interstellar” for this reason. The two previous interstellar objects observed by astronauts were 1I/’Oumuamua and 2I/Borisov, discovered in 2017 and 2019 respectively. The fact that all known interstellar visitors to our solar system have been discovered in the last decade is a sign of great strides in astronomical technology, but it also means that we have so far been able to collect very little data on interstellar comets. One thing stands out, however. Both 1I/’Oumuamua and 2I/Borisov came from the direction of the center of the Milky Way, but 3I/ATLAS came from a perpendicular angle.
Based on the trajectory, it is likely that the comet originated in a part of the galaxy that astronomers have not even observed yet. NASA is collecting 3I/ATLAS images, as is the European Space Agency, and both expect to have more satellite and probe data ready to be analyzed by early 2026; however, it is highly unlikely that we will ever be able to identify the exact origin of the comet. While scientists don’t know where it came from, they have a good idea where 3I/ATLAS is going, and you can rest assured that it won’t hit Earth. In fact, the comet will not even come as close to us as the sun.
Why do some people still think that 3I/ATLAS is a piece of alien technology
NASA image of comet 3I/ATLAS – Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI)
The intrusion of an interstellar object into our solar system immediately caught the attention of every alien enthusiast out there, and not just the typical podcast conspirators. A professor at the Harvard Center for Astrophysics is arguing that 3I/ATLAS could be a piece of alien technology. Professor Avi Loeb has published several articles on the interstellar object on his blog, which go against the consensus of his peers in the scientific community. He argues that 3I/ATLAS shows several anomalies compared to the two previous interstellar comets that have been tracked through our solar system. Compared to that pair, 3I/ATLAS is much more massive, but moves faster. He also notes that the gas plume around 3I/ATLAS contains similar levels of nickel to industrial alloys.
The radio signals recently recorded by 3I/ATLAS are another blow to Loeb’s theory, which has been roundly rebuked by other astrophysicists. Counterarguments point out that comets often show inconsistent characteristics. It is impossible to tell what is normal and what is anomalous, and this is especially true in the case of interstellar comets. Loeb actually hits the nail on the head in an article titled, The Tale of 3I/ATLAS and Sterile Neutrinos, where he asks, “How can anyone claim to be an expert on interstellar objects when the sample size includes only two previously known examples?” Most likely, many of our questions about 3I/ATLAS will not be answered until we observe other interstellar comets in the future.
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