Ever since 3I/ATLAS broke into our Solar System last July, astronomers haven’t taken their eyes off it. It’s one of those presences that come from outside, pass through our house as if nothing had happened and, just as we get used to the idea, they bring out another surprise. The latest came from South Africa, where the MeerKAT radio telescope, with its 13.5 meter dish, picked up the first radio signature associated with what appears to be an interstellar comet.
No flashes, no signals “coming from who knows where” like in the movies. The discovery, which occurred on October 24, 2025 after two failed attempts, is much more sober and at the same time more intriguing: radio absorptiona sort of imprint left between 1.665 and 1.667 GHz.
A technical detail for those observing space, but a fundamental clue to what 3I/ATLAS really is.
The signature of the hydroxyls, the debate on the nature of the object and that insistence of mystery
The detection is thanks to the team led by Professor DJ Pisano of the University of Cap, supported by Avi Loeb, a well-known name among those who move between astrophysics and alternative theories. According to the researchers, the absorption recorded by MeerKAT is compatible with the presence of OH radicalsthose molecular fragments that form when water meets sunlight.
This is where the story lights up, because 3I/ATLAS is an object that still eludes definitions. On the one hand there are those who consider it an interstellar comet; on the other hand, those who continue not to exclude a more “constructed” origin, perhaps artificial. No confirmation, of course, just an invitation not to take for granted what passes through deep space.
The presence of hydroxyls, however, tells something very earthly: ice reacting to solar radiation. A feature much closer to a comet than to an inert or metallic object.
On board this detail, astronomers also managed to estimate the surface temperature: approximately –43 °C. A frost that preserves the volatile materials, which could be released as the object continues its approach to the Sun. At the time of the measurement it was located at 1.38 times the Earth–Sun distancean area where the heat begins to be felt, even for an interstellar traveler.
The picture that emerges is that of a body that is not just any rock at all, but a fragile mixture sensitive to light, as if it were carrying a baggage of materials ready to transform.
The thought inevitably runs to the signal Wow!
There is one last coincidence that continues to haunt 3I/ATLAS: its trajectory seems to point towards the same region from which, in 1977, the famous Wow signal!that radio pulse that has divided skeptics and dreamers for decades.
No one is saying the two are connected, but the question remains there, stubborn, as the best questions often do. Astronomers hope that in the coming weeks the probe Junoaround Jupiter, is able to scan lower frequencies and collect data that MeerKAT cannot intercept from the ground.
For now we know this: 3I/ATLAS has spoken, in its own way. And the scientific community is preparing to listen to it again.
