A mysterious visitor from interstellar space has revealed its true identity. Astronomers using South Africa's MeerKAT radio telescope have detected the first radio signal from interstellar object 3I/ 'ATLAS and confirmed the object is a natural comet, not an alien spacecraft.
What have scientists discovered about 3I/ATLAS?
The object, first spotted in July 2025, is only the third interstellar body ever seen passing through our solar system. Travelling at more than 210,000 kilometres per hour, it was ejected from a distant star system billions of years ago. When it reached its closest point to the Sun on 29 October, MeerKAT detected a faint but distinct radio signal.
Researchers identified the emission as coming from hydroxyl radicals, formed when sunlight breaks apart water vapour in the comet’s coma — the cloud of gas and dust around its icy core. The signal confirmed active outgassing, a typical feature of comets, providing direct evidence of water and chemical activity.
Why is this discovery important?
For months, speculation swirled online that 3I/ATLAS could be an alien probe. Harvard astrophysicist Avi Loeb, known for his controversial views on extraterrestrial technology, suggested the object might be artificial. However, scientists say the new data leaves little doubt. “The radio signature is exactly what we’d expect from a water-rich comet,” said one researcher. “It behaves naturally — nothing alien about it.”
Astronomers also linked the finding to earlier spacecraft observations showing powerful jets of water erupting from 3I/ATLAS “like a fire hose” as it neared the Sun. Together, the two studies confirm that the object formed around seven billion years ago in another star system before being flung into interstellar space.
How does the signal help scientists?
Hydroxyl radicals emit a peculiar radio wavelength that telescopes like MeerKAT can detect. This allows astronomers to identify the presence of water and study chemical processes in distant objects. It opens up new avenues for scientists to track how comets evolve across star systems and what materials exist beyond our own.
What about the alien theories?
Since its discovery, 3I/ATLAS has been at the centre of viral speculation, echoing the debate that followed the first known interstellar visitor, ‘Oumuamua, in 2017. Yet experts say features once viewed as mysterious — shifting colours, brightness changes, and strange tails—are all consistent with known comet behaviour.
“Natural explanations fit the evidence best,” astronomers said, noting that both ‘Oumuamua and 3I/ATLAS likely share similar origins as icy remnants from other stars.
What does this mean for future research?
Scientists see this as a turning point for interstellar studies. Observing 3I/ATLAS has offered insights into how water and organic molecules form in other planetary systems. With new observatories such as NASA’s Square Kilometre Array (SKA) soon to join the search, researchers expect many more interstellar visitors to be found.
Each, they say, will act as a messenger from another world, carrying the chemical fingerprints of its birthplace — silent travellers revealing the shared story of our galaxy.
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