Comet C/2025 K1 (Atlas) breaks up

When a comet reaches perihelion — its closest approach to the Sun — its nucleus experiences significant stress, which increases as the distance decreases. In some cases, the solar radiation (which also produces the comet’s coma and tail) becomes so intense that it causes the comet to break apart into pieces. In even rarer cases, comets that pass particularly close to the Sun’s surface, the so-called sungrazers, can disintegrate completely.

Comet  C/2025 K1 (Atlas), discovered in May 2025, is a relatively unimportant object, shining barely at magnitude 10, i.e. well below the naked eye visibility threshold. After passing perihelion on October 8, 2025, it came back into view in the wee hours just before dawn.

Recent reports indicate that its nucleus has broken apart into at least two fragments. Its perihelion distance was quite close to the Sun at 0.33 AU—approximately the same as Mercury’s perihelion. In such close proximity to the Sun, temperatures are extremely high, likely causing the nucleus to heat up rapidly beyond its structural strength.

The rupture is obvious in pictures acquired through amateur-class equipment, like the one below, taken by myself in the morning of November 12, 2025. This image is the stack of 30 5-second frames, taken through a 10-inch GSO RC, an AP 0.67x reducer, a Touptek 2600 CMOS mono camera and an Optolong L filter. To enhance the details, frames were individually deconvolved in PixInsight prior to stacking. The two fragments are about 9 pixels apart in my image, i.e. about 5 arcsec. Since the comet was about 0.56 UA (i.e., 84 million km) away from us at the time the image was acquired, this yields an actual distance of approximately 2000 km. 

Enjoy! 🙂