Hubble Captures Rare Comet Fragmentation in Space

NASA’s Hubble Space Telescope has recorded a comet breaking apart in near real time, an event that is exceptionally rare to witness. This observation provides scientists with a unique opportunity to study the internal structure of one of the solar system’s ancient icy bodies.

Unexpected Comet Breakup Observation

The comet, designated C/2025 K1 (ATLAS), was not the original target of the Hubble observation campaign. John Noonan, a research professor at Auburn University’s Department of Physics, explained that the team had to select a new comet after their initial target became unobservable due to technical constraints. “Right when we observed it, it happened to break apart, which is the slimmest of slim chances,” Noonan said.

He discovered the fragmentation only after reviewing the images the day following the observation. “I saw that there were four comets in those images when we only proposed to look at one,” he noted, highlighting the rarity of capturing such an event.

Details of the Comet’s Fragmentation

Hubble’s sharp imaging revealed that comet K1 split into at least four distinct fragments, each surrounded by its own coma, the cloud of gas and dust enveloping a comet’s nucleus. Ground-based telescopes had previously only detected faint, indistinct bright spots that could not be clearly separated.

The breakup occurred roughly one month after K1 passed perihelion, traveling inside Mercury’s orbit at about one-third of Earth’s distance from the Sun. This proximity subjects comets to intense heat and stress, often causing long-period comets like K1 to begin disintegrating shortly after.

Prior to fragmentation, K1 was estimated to be about 5 miles in diameter, somewhat larger than an average comet. Scientists believe the breakup process started approximately eight days before Hubble’s observations, which included three 20-second exposures taken on November 8, 9, and 10, 2025. During this period, one smaller fragment also split further.

Insights Into Comet Composition and Brightness

Dennis Bodewits, principal investigator and physics professor at Auburn University, described comets as remnants from the solar system’s formation era, composed of primordial materials altered by solar heating and cosmic radiation. “By cracking open a comet, you can see the ancient material that has not been processed,” he said.

Researchers traced the fragments backward to determine when they were still a single object, reconstructing the breakup timeline. They encountered an unexpected puzzle regarding the comet’s brightness: it did not brighten immediately after splitting, despite fresh ice being exposed. Possible explanations include the formation of a dry dust layer over the ice or gradual heat penetration causing delayed dust ejection.

Noonan emphasized the significance of the timing: “Never before has Hubble caught a fragmenting comet this close to when it actually fell apart. Most of the time, it’s a few weeks to a month later. This is telling us something very important about the physics of what’s happening at the comet’s surface.”

Ongoing Analysis of Comet Chemistry

Early ground-based observations indicate that K1 exhibits unusual chemistry, with significantly less carbon than typical comets. Further spectroscopic studies using Hubble’s Space Telescope Imaging Spectrograph (STIS) and Cosmic Origins Spectrograph (COS) aim to provide more details about the comet’s composition and offer clues about the early solar system.

Currently located about 250 million miles from Earth in the constellation Pisces, K1 is moving away from the solar system and is unlikely to return.

Hubble’s Continued Contributions

Operating for over 30 years, the Hubble Space Telescope remains a vital tool for advancing knowledge of the universe. It is a collaborative project between NASA and the European Space Agency (ESA). NASA’s Goddard Space Flight Center manages the mission and telescope operations, supported by Lockheed Martin Space. The Space Telescope Science Institute in Baltimore oversees science operations for NASA.

The findings were published in the journal Icarus in the paper titled “Sequential fragmentation of C/2025 K1 (ATLAS) after its near-sun passage” by D. Bodewits and colleagues, dated February 6, 2026 (DOI: 10.1016/j.icarus.2026.116996).