3I/ATLAS Paints Space in Colour: Comet's Plasma Halo Offers Rare Cosmic Insight

A remarkable celestial event has given astronomers an unparalleled view of the universe. The comet 3I/ATLAS recently painted the void with an ethereal plasma halo, offering scientists a precious, fleeting glimpse into the mechanics of space.

This vibrant spectacle illuminates a crucial cosmic insight, underscoring the dynamic beauty hidden within our solar system.

A Rare Glimpse: Painting the Void

Writing on Medium in his latest piece, 'Charged Particles Map of 3I/ATLAS', Avi Loeb confessed that the photograph captured on 9 December, using the Canary One 0.5-metre telescope, rendered him utterly silent. Loeb highlighted that the picture provides a nearly complete, sharp depiction of its charged particles.

'And when I started connecting the dots between the "cupcake," Avi's latest article on X-rays, and this new image... a story emerged that I'd like to share,' he wrote.

The photograph was displayed; although the 77% Moon phase increased the background light, a spectacular sight of 3I/ATLAS was still achieved. The subsequent picture showed a close-up of 3I/ATLAS. Loeb commented: 'You can do the same by downloading the image above.'

The colour, as explained by Loeb, results from the telescope's RGB method — three separate filtered-light measurements (R, G, B) merged into a single image. He added: 'And what we see here is incredible.'

He encouraged observers to inspect the entire colour progression surrounding 3I/ATLAS, highlighting that the spectrum begins on the right with turquoise and violet, transitions to red–orange, passes through a consistent yellow, and completes the circle with a profound green.

Earlier RGB-filter measurements typically revealed only yellow-green shades within the inner coma. 'I have never seen clearly separated blue or orange-red regions around 3I/ATLAS until today,' Loeb said. He maintained that this phenomenon is neither an optical delusion nor a 'rainbow in space'. Instead, it represents the particles' physical activity.

Photon Energy Dictates Colour

The relationship between the energy levels of photons and their corresponding colour is direct:

• When solar light is dispersed by dust or plasma:
• Elevated-energy wavelengths produce blue and violet hues.
• Intermediate energies result in green and yellow.
• Reduced-energy, thermal waves generate orange and red.

Consequently, the resulting picture illustrates precisely which light particles succeeded in travelling outward across every vector.

Charge Exchange: The Chemical Portrait

The resulting blue and green light is the central finding, aligning precisely with the charge exchange phenomenon Avi Loeb detailed in his piece on X-rays.

When the solar wind interacts with the gaseous envelope surrounding 3I/ATLAS, its ions strip electrons from neutral atoms (Carbon, Nitrogen, Oxygen).

These elements subsequently radiate light in highly distinct shades:

• Oxygen yields green.
• Nitrogen results in violet or blue.
• Carbon generates blue-turquoise.

Consequently, this observation constitutes a chemical depiction of the ongoing charge-exchange process.

Segmented Zones: Plasma Dynamics

The appearance of hues in distinct sections (such as a blue–violet rear, a yellow–orange frontal area, and a green core) confirms that the material is unevenly spread.

What accounts for this striking effect in 3I/ATLAS?

Loeb suggests several explanations:

• The comet's interior dust cloud is exceptionally compact and luminous, enhancing the comet's visible colours.
• Its extreme velocity (60–70 km/s) intensifies the charge-exchange interaction.
• It possesses metal-rich or highly energetic constituents, consequently elevating ion emission.

Outgassing streams influence the flow, producing segmented colour areas rather than a uniform ring.

The Luminous Plasma Blaze

This photograph reveals precisely how an interstellar object engages with the solar wind and magnetic field, resulting in a vibrant colour trace from its atoms. This interaction's potential impact was recently explored in Loeb's 'Black Hole Jets' article.

Loeb's latest comment, confirming that 3I/ATLAS exhibits X-ray characteristics consistent with charge-exchange interactions, clarifies the situation: the inner coma appears to function somewhat like a glowing plasma. This is not an actual flame, but rather a zone where ionised matter temporarily forms a structure before spreading out, which is precisely visible in the current photograph.

Loeb proposed that this self-organised area might be the 'cupcake' feature described previously—the internal plasma zone located below the vibrant outer casing. The contouring procedure detects its shape within the brilliant white centre, and the spectrum of colours surrounding it demonstrates how those particles behave as they move away and undergo charge exchange within the coma.