NASA Missions Monitor 3I/ATLAS: Explosion Of The Ion Tail Grows

Even with a bright Moon spoiling the view, a visitor from another star system is making its presence known. Interstellar comet 3I/ATLAS (C/2025 N1 ATLAS) is not just passing through; it is actively putting on a show. A dramatic new image captured by the Virtual Telescope Project reveals the comet's ion tail has grown significantly longer and more structured, a clear sign of intensifying activity on its journey past our Sun.

The image, captured at 11:31 p.m. EDT on 10 November (0431 GMT on 11 November), is a composite of 18 separate 120-second exposures. It was remotely taken by robotic telescopes in Manciano, Italy. Astronomers faced challenging conditions: the comet was just 14 degrees above the eastern horizon, and a bright 61% Moon shone about 70 degrees away. Despite this, a sharply defined, luminous ion tail is clearly visible.

'Exploiting the unusual good weather of this season, we imaged the interstellar comet 3I/ATLAS (C/2025 N1 ATLAS) again, recording a much more developed ion tail', Gianluca Masi, Virtual Telescope Project founder and astronomer, said in a post sharing the new image. 'Looking at the picture, we see how the ion tail of 3I/ATLAS is clearly showing better and better'.

This ground-based observation is just one piece of a massive, coordinated effort to study the comet. A fleet of space-based missions from NASA and ESA are also monitoring 3I/ATLAS, turning their instruments towards the visitor to gather as much data as possible.

What Makes the Tail of 3I/ATLAS Glow?

This impressive tail is a fascinating display of solar physics. An ion tail forms when the Sun's ultraviolet radiation strips electrons from gas molecules released by the comet, a process called ionisation. This turns them into charged ions. These ions are then captured and swept away by the solar wind—a constant stream of charged particles flowing outward from the Sun. This process creates a long, often bluish tail that always points directly away from the Sun, regardless of the comet's direction of travel. This is different from a comet's dust tail, which tends to appear yellowish-white and curves gently along its orbital path.

Analysing the New View of 3I/ATLAS

In the new image, the comet's bright core is surrounded by a compact coma and a sharply defined ion tail stretching roughly 0.7 degrees across the sky. A faint anti-tail (a feature caused by the observer's perspective as dust trails along the comet's orbit) can also be seen extending in the opposite direction. This image shows a clear increase in activity compared to earlier observations. It strongly suggests that 3I/ATLAS is venting gas and dust more vigorously as it reacts to the Sun's increasing heat.

This reported growth is not just in length. Other observations from early November have revealed an even more complex 'explosion' of activity, showing the comet's tail fanning out into four or five distinct jets. This dramatic structure is the result of the comet shedding significant amounts of material. This tail has become so expansive that in late October and early November, two spacecraft—ESA's Hera and NASA's Europa Clipper—were predicted to have been fully immersed in it, flying directly through the particles streaming from this interstellar visitor.

A Rare Glimpse of an Interstellar Visitor: 3I/ATLAS

3I/ATLAS is only the third confirmed interstellar object ever detected, following 1I/'Oumuamua in 2017 and 2I/Borisov in 2019. This rarity is what makes it so exciting. Unlike its predecessors, this visitor from another star system is bright enough to be studied in detail by ground-based telescopes. This includes world-class observatories like NASA's Hubble Space Telescope and the James Webb Space Telescope, which have already provided crucial data on its size and chemical composition. NASA's Swift and IRTF observatories, along with ESA's Mars orbiters, have also studied the comet, creating an unprecedented campaign to understand this object from another star.

The growing length and brightness of the tail suggest increasing sublimation of volatile materials (likely including carbon dioxide and dust) which are then swept into space by the solar wind. This activity provides vital clues to its composition. Early data suggest that 3I/ATLAS may contain a high fraction of carbon dioxide ice. This offers potential clues to the conditions in the distant planetary system where it formed, as well as valuable insight on how comets evolve beyond our solar neighbourhood.

The Virtual Telescope Project will continue to monitor 3I/ATLAS as it travels through the inner solar system. You can check out past images of the comet taken since it was first detected in July of this year.

As 3I/ATLAS continues its fleeting journey through our inner solar system, it promises to reveal more secrets about its distant origins. The global scientific campaign is far from over, offering a rare, real-time glimpse into a visitor from another star. Don't miss this cosmic event—follow the Virtual Telescope Project and updates from NASA and ESA for the latest images and discoveries as this interstellar traveller continues its spectacular show.