Comet C/2025 K1 (ATLAS) Breaks Into Multiple Fragments After Solar Approach

Comet C/2025 K1 (ATLAS), a dynamically new object from the Oort cloud, underwent fragmentation following its close approach to the Sun in late 2025. The event was observed using both ground-based telescopes and the Hubble Space Telescope, providing detailed views of the breakup process.

The comet reached its closest distance to the Sun, approximately 0.33 astronomical units, on October 8, 2025. Shortly after this perihelion, a notable increase in brightness was recorded between November 2 and 4, 2025, preceding the detection of multiple fragments.

Between November 8 and 10, 2025, the Hubble Space Telescope captured high-resolution images that resolved at least five distinct fragments of the comet. These observations were made using the STIS instrument and occurred during serendipitous acquisition imaging.

Simultaneously, ground-based observatories reported the comet splitting into three or possibly four visible pieces during early to mid-November 2025. Images from the Virtual Telescope Project and other observatories between November 11 and 19, 2025, confirmed the presence of three main fragments and suggested a possible fourth.

What the numbers show

• Perihelion occurred at 0.33 astronomical units from the Sun on October 8, 2025
• Hubble images from November 8–10, 2025, resolved at least five fragments
• Ground-based images between November 11–19, 2025, confirmed three main fragments

The comet was initially detected on May 24, 2025, by the ATLAS survey system. Its origin in the Oort cloud classified it as dynamically new, and it was not expected to withstand the stresses of its close solar passage.

The fragmentation sequence observed by Hubble was hierarchical, with primary and secondary breakups occurring one to three days before increases in brightness. This pattern was documented through both space-based and ground-based imaging during November 2025.

Analysis of the breakup suggests that rotational instability, likely caused by enhanced outgassing torques after the comet's close approach to the Sun, contributed to the disintegration. The timing of the observed outbursts and fragmentations supports this explanation.

The event provided astronomers with a rare opportunity to study the disintegration of a dynamically new comet from the Oort cloud. The combination of space-based and ground-based observations allowed for detailed tracking of the fragmentation process over several weeks.

* This article is based on publicly available information at the time of writing.