Teide Telescope Makes Pioneering Interstellar Comet Discovery
Observations from the two-metre twin telescope at the Teide Observatory in Tenerife have led to a pioneering breakthrough in astronomy: the first detection of a wobbling jet of gas and dust on a comet of interstellar origin, 3I/ATLAS. The comet reaches its closest point to Earth tomorrow. The study, published in the journal ‘Astronomy & Astrophysics’, provides the first evidence of localised activity from an interstellar nucleus and offers a unique view into the nature of a celestial body formed outside our Solar System, as announced by Light Bridges, the managers of the robotic telescope, on Thursday.
An “Extraordinarily Normal” Interstellar Visitor
The research was led by Miquel Serra-Ricart, scientific director of Light Bridges, with co-authors Javier Licandro, a researcher at the Instituto de Astrofísica de Canarias (IAC), and Miguel R. Alarcón, a pre-doctoral researcher at the IAC and scientific operations director at Light Bridges. Miquel Serra-Ricart detailed that, last July, based on variability in the comet’s brightness, the researchers were the first to pinpoint 3I/ATLAS’s rotation period of around 17 hours. “Now we report the first jet in an interstellar comet which, furthermore, confirms the rotation calculated in July,” he said.
Serra-Ricart, administrator of the Teide Observatory for 30 years, also highlighted the object’s surprising familiarity despite its origin. “3I/ATLAS is an extraordinarily normal interstellar comet. Detecting this jet allows for a direct comparison with the activity mechanisms observed in comets from our own Solar System.” Javier Licandro added, “Characterising jets in a body like 3I/ATLAS represents a unique opportunity to investigate the physical behaviour of a pristine body formed in another planetary system.”
Intensive Observation Campaign Reveals Hidden Structure
The key observations were made with the Two-metre Twin Telescope (TTT) at the Teide Observatory during an intensive 37-night campaign between July and September 2025 as part of the PLANETIX25 project. The team pushed the storage and computing capabilities at ASTRO POC to their limit to focus on the structures within the inner coma of 3I/ATLAS, the third confirmed interstellar object.
Using an image filtering technique known as a Laplacian transformation, the researchers detected a faint but defined jet of gas and dust emanating from the nucleus. “This is the first proof that an interstellar nucleus presents such a focused release of material,” they detailed.
Wobbling Jet Confirms Comet’s Rotation
The most significant finding was that the jet did not remain static. A detailed analysis of its position revealed a small but significant periodic modulation around the nucleus’s spin axis. This oscillation of the jet, the first of its kind detected in an interstellar comet, allowed scientists to deduce the nucleus’s rotation period.
It was concluded that the rotation period of comet 3I/ATLAS is between 14 and 17 hours if the jet originates near one of the poles, confirming measurements taken by researchers from the IAC, the Grantecan telescope, and the Complutense University of Madrid last July, also using TTT data.
The researchers added that cometary jets are key tracers of nucleus activity and rotational state. They noted that the methodology enabling this discovery was an optimal filtering of the images, which enhances the faint and anisotropic structures of the jet against the bright background of the coma. This advanced analysis significantly contributes to understanding how volatiles and dust behave in bodies that, like 3I/ATLAS, have travelled through interstellar space and contain original material from the formation of an alien planetary system.
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