Ancient interstellar comet 3I/ATLAS fades as it drifts from the Sun

Interstellar comet 3I/ATLAS has dimmed significantly in recent days. Its brightness has dropped by over a third, with its apparent magnitude rising from 10.1 to 10.6. This makes it only 63% as bright as it was six days ago. The fade in brightness is mainly due to the comet moving farther from the Sun. At the same time, its distance from Earth has decreased by 10 million kilometres. The object remains one of the most notable in the sky, ranking as the fourth-brightest among nearly 100 visible comets.

3I/ATLAS is a visitor from another star system. It has a coma roughly 24 kilometres wide and displays an unusual, ragged tail in recent images. Computer models suggest it is over 7.5 billion years old, making it possibly the oldest comet ever observed. It is also about 3 billion years older than the Sun.

The comet will make its closest approach to Jupiter on 16 March 2026. The comet’s behaviour and structure continue to intrigue astronomers. Its decreasing brightness reflects its movement away from the Sun. Observations will likely continue as it travels through the solar system.