Hubble Accidentally Captures a Comet Breaking Apart in Real Time, a First for the 35-Year-Old Telescope
NASA's Hubble Space Telescope caught comet C/2025 K1 fragmenting into at least four pieces across three days, marking the closest-to-breakup observation in the telescope's history.
Overview
NASA’s Hubble Space Telescope has captured a comet in the act of breaking apart — something astronomers have attempted to observe for decades but never managed to witness so close to the moment of fragmentation. The findings, published in the journal Icarus on March 18, 2026, describe how the telescope caught comet C/2025 K1 (ATLAS) splitting into at least four distinct pieces across three consecutive days in November 2025, according to NASA.
The discovery was entirely accidental. The research team had originally planned to observe a different target, but when that object became unavailable due to scheduling constraints, they pivoted to K1 — and happened to point the telescope at the comet just days after it began to disintegrate.
What We Know
Comet C/2025 K1 (ATLAS) measured approximately five miles across before it broke apart, roughly one month after reaching perihelion — its closest approach to the Sun, which brought it inside Mercury’s orbit to about one-third of Earth’s distance from the Sun, according to NASA.
Hubble took three 20-second exposures on November 8, 9, and 10 of 2025, capturing the progressive disintegration. Each fragment displayed its own distinct coma — the fuzzy envelope of gas and dust that surrounds a comet’s icy nucleus — as the pieces drifted apart at a distance of roughly 250 million miles from Earth in the constellation Pisces, as reported by ScienceDaily.
The research team, led by principal investigator Dennis Bodewits and co-investigator John Noonan of Auburn University’s Department of Physics, estimated that the breakup had begun approximately eight days before Hubble’s first observation, according to ScienceDaily. Never before has Hubble caught a fragmenting comet this close to the actual moment of disintegration; most prior observations came weeks to a month after the fact.
“Sometimes the best science happens by accident,” Noonan said, describing the observation as “the slimmest of slim chances,” according to NASA. Bodewits added: “The irony is now we’re just studying a regular comet and it crumbles in front of our eyes,” as reported by ScienceDaily.
A Chemically Unusual Comet
Spectroscopic analysis revealed that K1 is chemically distinctive. The comet is significantly depleted in carbon compared with other known comets, according to Phys.org. Because comets are frozen relics from the early solar system, their composition offers a window into conditions that existed roughly 4.6 billion years ago. The exposed interior material from K1’s fragmentation gives scientists a rare opportunity to examine primordial building blocks that have been locked beneath the surface since the solar system’s formation.
Hubble’s STIS (Space Telescope Imaging Spectrograph) and COS (Cosmic Origins Spectrograph) instruments collected additional spectroscopic data that the team expects will reveal further compositional details, according to Phys.org.
What We Don’t Know
The observations raised a scientific puzzle that remains unresolved. When K1 fragmented and exposed fresh ice to sunlight, the comet did not immediately brighten as expected. Ground-based telescopes detected no corresponding outburst in the days following fragmentation, according to NASA.
The research team has proposed two possible explanations: either a layer of dry dust needs to form over the exposed pure ice before it can be blown off by sublimation, or heat must build sufficient subsurface pressure to eject dust shells. Neither mechanism has been confirmed, and the delayed brightening timeline remains an open question for cometary science, according to Phys.org.
It is also unclear what triggered the breakup itself. Thermal stress from the intense solar heating at perihelion is the leading candidate, but the precise failure mechanism — whether the nucleus cracked due to uneven heating, rotational spin-up, or some combination — has not been determined.
Analysis
The observation is notable not only for its scientific content but for what it says about the value of flexible scheduling on aging space observatories. Hubble, now 36 years into a mission originally designed for 15, continues to produce results that no other instrument can replicate. Its ultraviolet and visible-light imaging capabilities remain unmatched for this type of close-in cometary observation, and the serendipitous nature of this discovery underscores how much of the solar system’s behavior occurs beyond the reach of planned observation campaigns.
The K1 fragmentation also adds to a growing body of evidence that comets are structurally weaker and more heterogeneous than previously assumed. Each breakup event observed in detail refines models of how these ancient objects hold together — and how they fall apart when pushed beyond their limits by solar radiation.