C/2025 K1 ATLAS

Closest to Earth:  2025 Nov 24 at 0.40AU
Closest to Sun:   2025 Oct 8 at 0.33AU
Maximum magnitude: ?8 in January 2026 (disintegration risk)
Orbital Period: N/A dynamically new

C/2025 K1 ATLAS showing a split nucleus (3 fragments) on 2025 December 1.



C/2025 K1 ATLAS on 2025 November 25

The ATLAS South Africa survey discovered this comet on 2025 May 24.
It is expected to reach perihelion on 2025 October 8 at a distance of 0.33 AU, near Mercury's orbit.
Current estimates indicate that the comet could attain a peak brightness of magnitude 6.

However, according to the “Bortle survival limit” formula, it faces a significant risk of disintegration due to its low intrinsic luminosity
and dynamically new orbit, as this will be its first and only approach to the inner solar system.

It will have two close encounters with the Earth.
On its inbound passage it will be 0.57 AU away on 2025 August 12.
On 2025 November 24, it will be 0.40 AU away on its outbound journey.
The inbound passage favours southern hemisphere observers and should give us the opportunity to watch its demise (or not).
Watch closely for outbursts or unusual behaviour.

During September 2025, the comet may brighten from magnitude 11 to 8 as it moves through the constellations of Libra and Virgo during evening hours.

Moonlight affects visibility during early September, disappearing by September 9, when the comet is positioned near the border of Libra and Virgo,
close to Kappa Virginis. It will be within 30’ of that star on September 12 and shining at magnitude 10.5.

On September 20, it locates 2 degrees south of Mars.

Although it may have brightened to magnitude 8.5 by then, its rapid motion sunward will start to make it more difficult to spot.

On the evening of September 24, the comet will situate near Spica (Alpha Virginis) and the crescent moon.
It will pass 3 degrees north of Spica on the evening of the September 26.

Final observations are expected by months end, at which time the comet may reach a magnitude of 7.5 or, alternatively,
may have disintegrated into a dust cloud.

Should the comet miraculously defy the odds, it will reappear in morning skies during late October, suiting northern viewers.

UPDATE: comet underwent several fragmentation episodes post-perihelion.