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 Terrestrial-impact Last Alert System (ATLAS). Although comets pass by Earth regularly, the most famous being Halley’s Comet, there is something extra special about this new discovery. Halley and other well-known comets originated in our solar system, born from the same planet-forming disk from which the Sun, Earth, and all 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 was emitting something.
South Africa’s MeerKAT radio telescope detected 3I/ATLAS in late October as the comet approached its closest point to the sun. This discovery was widely reported as radio signals emitted by 3I/ATLAS, leading conspiracy theorists to speculate that the object might actually be a piece of alien technology. However, this is not quite accurate. Technically, everything emits electromagnetic radiation, and what MeerKAT discovered was not an audio transmission like we hear on a car radio. What he actually found were gaps in the radio spectrum caused by absorption of radio waves by OH molecules, also known as hydroxyl radicals. OH molecules — the remnants of water broken up by solar radiation — are regularly observed in comets that pass within Earth’s reach, seemingly putting to bed any speculation that 3I/ATLAS is anything other than a comet. However, it does not answer the question of where 3I/ATLAS came from.
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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 stands for “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 past decade is a sign of great advances in astronomical technology, but it also means that we have been able to collect very little data so far about interstellar comets. But one thing stands out. Both 1I/’Oumuamua and 2I/Borisov came from the direction of the center of the Milky Way, but 3I/ATLAS comes from a perpendicular angle.
Based on the trajectory, it’s likely that the comet originated in a part of the galaxy that astronomers haven’t even noticed yet. NASA is gathering 3I/ATLAS imagery, as is the European Space Agency, and both expect to have more satellite and probe data ready for analysis by early 2026; however, it is highly unlikely that we will ever be able to pinpoint the exact origin of the comet. Although scientists don’t know where it came from, they have a good idea where 3I/ATLAS is going, and you can be sure it won’t hit Earth. In fact, the comet won’t even come as close to us as the sun.
Why some people still think 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 entry of an interstellar object into our solar system immediately caught the attention of every alien enthusiast out there, and not just your typical podcast conspiracists. A professor at the Harvard Center for Astrophysics claims that 3I/ATLAS could be a piece of alien technology. Professor Avi Loeb has published numerous articles about the interstellar object on his blog, going against the consensus of his colleagues in the scientific community. He claims that 3I/ATLAS exhibits several anomalies compared to the two previous interstellar comets that have been tracked through our solar system. Compared to that pair, the 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 recently recorded radio signals from 3I/ATLAS are yet another crack in Loeb’s theory, which has been strongly criticized by other astrophysicists. Counterarguments point out that comets often exhibit inconsistent characteristics. It is impossible to tell what is normal and what is abnormal, and this is especially true of interstellar comets. Loeb really hits the nail on the head in an article titled, The Story of 3I/ATLAS and the Barren Neutrinos, in which he asks, “How can anyone claim to be an expert on interstellar objects when the sample size includes only two previously known examples?” In all likelihood, many of our questions about 3I/ATLAS will not be answered until we observe other interstellar comets in the future.
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