Interstellar object 3I/ATLAS mystery solved: Astronomers detect first radio signal revealing its origins

Astronomers have detected the first-ever radio signal from the interstellar object 3I/ATLAS , marking a milestone in the study of visitors from beyond our solar system. The finding, made using South Africa’s MeerKAT radio telescope, confirms that the mysterious object is a natural comet, not an alien probe as some had speculated. Scientists say the discovery finally settles debates surrounding its true nature and origin.


3I/ATLAS: A mysterious visitor from another star system
3I/ATLAS, first observed in July 2025, is only the third interstellar object ever detected passing through our solar system. Travelling at more than 130,000 miles per hour (210,000 km/h), it was identified as an icy body ejected from a distant star system billions of years ago.

Its unusual brightness, shifting colour, and strange orbital behaviour initially puzzled astronomers — and fuelled speculation that it could be an artificial or alien-made object, echoing the debate that followed the earlier interstellar visitor ‘Oumuamua in 2017.

The first radio signal — and what it revealed
The breakthrough came when scientists at MeerKAT, a powerful array of 64 radio dishes, detected a faint but clear radio signal from 3I/ATLAS as it reached its closest approach to the Sun (perihelion) on October 29.
While some observers speculated about extraterrestrial origins, researchers quickly identified the signal as natural radio emissions produced by hydroxyl radicals (OH molecules) in the comet’s coma — the gas and dust envelope that surrounds its icy nucleus.

These molecules form when solar radiation breaks apart water vapour ejected by the comet, a classic sign of outgassing, the process that creates a comet’s glowing tail.

In short, the radio waves are not messages from aliens, but evidence of water and chemical activity, confirming that 3I/ATLAS behaves just like comets born within our own solar system.

A victory for science over speculation
Harvard astrophysicist Avi Loeb, known for his controversial theories about alien technology, had suggested that 3I/ATLAS might be an extraterrestrial probe. However, the new data undermines that hypothesis.
Loeb acknowledged the detection of hydroxyl radicals but stopped short of calling it proof of cometary behaviour.

Meanwhile, mainstream astronomers emphasised that the evidence is overwhelming: the radio signal matches known patterns of natural comet activity, not anything artificial or engineered.

The finding also aligns with NASA ’s earlier observations in October, when spacecraft detected powerful jets of water erupting from 3I/ATLAS “like a fire hose” as it neared the Sun. Together, the two discoveries confirm that the interstellar object is an ancient comet, likely formed up to seven billion years ago in the outer reaches of another star system before being flung into interstellar space.

The science behind the signal
Hydroxyl radicals are produced when ultraviolet light from the Sun interacts with water molecules, splitting them apart into hydrogen and oxygen. These radicals emit a distinct radio wavelength that can be detected by instruments like MeerKAT, offering astronomers a way to identify water activity — and, by extension, confirm whether an object is a true comet.

The detection of this specific radio wavelength from 3I/ATLAS provides direct proof of volatile compounds in its composition, resolving years of speculation about its origin.

“The radio signature is exactly what we’d expect from a water-rich comet,” said one researcher involved in the study. “It tells us that this object is behaving in a completely natural way — there’s nothing alien about it.”

Debunking the alien theories
Since its discovery, 3I/ATLAS has been the subject of viral online speculation, with conspiracy theorists claiming it could be a hidden spacecraft or alien beacon. Similar claims surrounded its predecessor, ‘Oumuamua, whose odd shape and acceleration pattern sparked years of debate.

But in both cases, detailed scientific analysis has shown that natural explanations fit the evidence best.
Astronomers point out that features once considered “strange” — such as an anti-tail, carbon dioxide emissions, and brightness fluctuations — are all well-documented cometary behaviours under intense solar radiation.

What 3I/ATLAS teaches us about the universe
The discovery is more than a rebuttal of alien theories — it’s a scientific leap forward. By studying interstellar objects like 3I/ATLAS, astronomers can trace the chemical composition of distant planetary systems, offering insights into how water and organic molecules form elsewhere in the galaxy.

With telescopes like MeerKAT and NASA’s upcoming Square Kilometre Array (SKA), researchers expect to detect many more such objects in the coming years. Each one, they say, is a messenger from another world, carrying the chemical fingerprints of its birthplace across the vast distances of space.

As one astronomer put it, “3I/ATLAS didn’t send us an alien message — it sent us something better: a message from the universe itself about where we come from.”