New Image Reveals Growing Tail of Interstellar Comet 3I/ATLAS

A recent image of interstellar comet 3I/ATLAS (C/2025 N1 ATLAS) has revealed a significant expansion of its ion tail. This dramatic growth indicates increasing activity as the comet travels through the inner solar system. The image was captured by the Virtual Telescope Project on November 10, 2023, at 11:31 p.m. EDT (0431 GMT on November 11). It comprises 18 separate 120-second exposures taken by robotic telescopes based in Manciano, Italy.

Comet Activity and Ion Tail Development

Despite visibility challenges—being only 14 degrees above the eastern horizon and under the glow of a 61% waxing moon—the ion tail of 3I/ATLAS was prominently visible. Gianluca Masi, the founder of the Virtual Telescope Project, noted the successful imaging, crediting favorable weather conditions for the opportunity. He stated, “Looking at the picture, we see how the ion tail of 3I/ATLAS is clearly showing better and better.”

Understanding Ion Tails

The formation of an ion tail occurs when the sun’s ultraviolet radiation interacts with gas molecules released by the comet. This process strips electrons from the molecules, turning them into charged ions that are propelled away by the solar wind. This creates a distinctive long, bluish tail that always points away from the sun, regardless of the comet’s trajectory. In contrast, the dust tail appears yellowish-white and follows the comet’s orbital path.

• Comet Core: Surrounded by a compact coma.
• Ion Tail Measurement: Approximately 0.7 degrees across the sky.
• Anti-Tail: A faint feature extending in the opposite direction due to the observer’s angle.

The recent image indicates a notable increase in the comet’s activity compared to previous observations. This suggests that 3I/ATLAS is actively venting gas and dust as it is warmed by the sun.

Significance of 3I/ATLAS

Notably, 3I/ATLAS is only the third confirmed interstellar object detected, following 1I/‘Oumuamua in 2017 and 2I/Borisov in 2019. Unlike its predecessors, this comet is bright enough to be observed in detail with ground-based telescopes. This provides astronomers with a unique chance to study the behavior of an interstellar comet influenced by our sun.

The expanding length and brightness of the ion tail suggest increased sublimation of volatile materials such as carbon dioxide and dust. Early data indicates that 3I/ATLAS may contain a significant amount of carbon dioxide ice. This finding could yield insights into the conditions of the distant planetary system where it originated and enhance our understanding of comet evolution beyond our solar neighborhood.

The Virtual Telescope Project plans to continue monitoring the comet for further developments as it moves through the inner solar system. Observers can review previously captured images since its initial detection in July 2023.