The first-ever detection of a radio signal from the interstellar comet 3I/ATLAS when it passed near the Sun in late October 2025 is a significant development in understanding comets from outside our solar system and how they behave near our Sun.
What Is 3I/ATLAS?
3I/ATLAS is the only third object believed to be interstellar to come visit our solar system from another star. Discovered in July 2025, it attracted a lot of attention because of its less typical path, and because it has been in the outer solar system and not advanced toward Earth at all—at the last update it was not any closer to Earth than just on the inside of the orbit of Mars.
How Did The Radio Signal Get Detected?
After not detecting anything from it in September, on October 24, 2025 – astronomers reported detecting faint radio signals from 3D/ATLAS with the MeerKAT radio telescope in South Africa – right before the objects closest approach to the sun. These signals weren’t just “missed” signals or communications from aliens – they were actually signals resulting from special dips in the radio waves, known as absorption lines, resulting from the presence of hydroxyl (OH) molecules within the atmosphere.
Why Is This important?
Detecting a radio signal from an interstellar comet is a first in and of itself, plus it is evidence of water on 3I/ATLAS. The sunlight near the object provides indications of where water molecules have dissociated into OH molecules. This is helpful for astrophysicists to confirm that 3I/ATLAS is not artificial!
What Happens Next?
The hope is that the astronomers will continue to observe 3I/ATLAS as it leaves the Sun and possibly observe other signals and learn more about its origin and general composition. This research opens up a new possibility for how we study interstellar visitors to our solar system with radio telescopes.
This summary is for informational purposes only; interpretation of scientific findings may evolve with further research.
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