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Astronomers observing the interstellar comet 3I/ATLAS have identified behaviour that challenges long-standing models of comet physics. Using telescopes based in Tenerife, researchers detected a persistent, rotating jet of dust and gas emerging from the comet’s nucleus — a feature that behaves very differently from what is normally observed in comets originating within our Solar System.
Instead of producing short, chaotic bursts of material as surface ice heats up near the Sun, 3I/ATLAS appears to lose mass in a steady and organised way, with the jet rotating in sync with the comet itself.
An Unusual Pattern of Activity
Scientists describe the behaviour as closer to a controlled “bleeding” of material than the explosive outgassing normally associated with comets. The particles detected within the jet are also larger and heavier than expected, and the rate of material loss remains stable over extended observation periods.
Researchers also identified a visible anti-tail, an optical effect where dust appears to point toward the Sun rather than away from it. While anti-tails have been seen before, their presence alongside such a stable jet further highlights how unusual 3I/ATLAS is.
A Visitor From Beyond the Solar System
3I/ATLAS was discovered in July 2025 by the ATLAS survey system and was quickly confirmed to be interstellar, following a hyperbolic orbit that shows it is not gravitationally bound to the Sun. It is only the third confirmed interstellar object ever observed passing through our Solar System.
The comet reached perihelion in late October 2025 and made its closest approach to Earth in December. Although it posed no threat, its trajectory provided scientists with a rare opportunity to study material that likely formed around another star.
Why the Discovery Matters
The steady jet and rotational behaviour observed from Tenerife suggest that interstellar comets may have internal structures or surface compositions fundamentally different from those formed closer to the Sun. This challenges existing theories about how cometary activity begins and evolves.
As more advanced telescopes come online and future missions aim to intercept similar objects, findings from 3I/ATLAS could help reshape scientific understanding of icy bodies arriving from other star systems — and what they can tell us about the wider galaxy.
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