Interstellar Comet 3I/ATLAS Turns Green Near Earth

Interstellar comet 3I/ATLAS has entered a highly active phase as it travels through the inner solar system, drawing scientific attention with its rapid brightening and unusual green glow. Recent observations show that the comet, originating beyond our solar system, is undergoing chemical and physical changes as it responds to solar heating, offering rare insights into material formed around distant stars.

Green Glow Signals Chemical Activity

Astronomers observed a distinct greenish hue emerging from the comet’s coma after its close solar approach in late October. This colour is produced by diatomic carbon (C₂) molecules released when frozen gases sublimate from the comet’s surface. When exposed to sunlight, these molecules emit green light, a common phenomenon in solar system comets but unexpected for 3I/ATLAS, which earlier appeared predominantly red.

Solar Heating Drives Brightening and Tail Formation

As 3I/ATLAS warmed, ice and dust trapped within its nucleus vaporised, forming a bright coma and an elongated tail illuminated by sunlight. Multi-filter observations indicate a shift in composition since pre-perihelion monitoring, suggesting fresh material is being exposed. Such delayed responses to solar heating are typical in comets and may trigger further outbursts in the coming days.

Rare Interstellar Visitor With Ancient Origins

3I/ATLAS is only the third confirmed interstellar object detected, following 1I/‘Oumuamua and 2I/Borisov. Travelling on a hyperbolic orbit at roughly 210,000 km/h, it will not return to the solar system. Scientists believe it may be among the largest and oldest interstellar bodies observed so far, preserving material from early star-forming environments.

What to Note for Exams?

• 3I/ATLAS is the third known interstellar object detected after ‘Oumuamua and Borisov.
• The comet’s green colour is caused by diatomic carbon molecules excited by sunlight.
• It follows a hyperbolic orbit and will permanently exit the solar system.
• Closest approach to Earth occurs at about 270 million kilometres.

Scientific Value for Studying Other Star Systems

With its icy composition, evolving jets, and changing chemistry, 3I/ATLAS acts as a natural laboratory for understanding interstellar material. Continued global observations aim to refine estimates of its size, structure, and composition, helping scientists reconstruct conditions in ancient star systems and deepen knowledge of how planetary material forms across the galaxy.