Rare comet Lemmon visible over Bengaluru skies

A faint green comet, officially designated C/2025 A6 (Lemmon), was briefly visible over Bengaluru’s western horizon on Saturday evening, offering a rare chance for skywatchers to observe an icy body from the outer Solar System within city limits.

Astrophotographer Deepak Choudhary, founder of the astronomy outreach platform thegreatbeyond.in, recorded the comet from the rooftop of the Co-Evolve high-rise using a William Optics Zenithstar 61 refractor telescope and ZWO ASI533MC camera.

The images show a green coma — the cloud of gas surrounding the comet’s nucleus and a short, faint dust tail, visible for only a few minutes before the object dipped below the skyline.

Comet Lemmon was discovered in January 2025 by the Mount Lemmon Observatory in Arizona, U.S., and has brightened gradually as it moves closer to the Sun. It is currently visible from the Northern Hemisphere through binoculars, though its brightness varies due to outgassing, the release of gas and dust as solar radiation heats the comet’s surface.

The green glow seen in images is not due to reflection but fluorescence from diatomic carbon (C₂), a molecule that emits green light when excited by ultraviolet sunlight. The gas exists only in the comet’s coma and quickly breaks apart, which is why the tail itself appears colourless, researchers told The Hindu.

Capturing the comet from within Bengaluru, a city known for its dense light pollution, was possible only under clear post-monsoon skies and careful timing, Mr. Choudhary said. “The window to image was just a few minutes before it dropped too low. Urban astrophotography is about precision more than location,” he added.