NASA’s Hubble Space Telescope has captured a rare cosmic moment: a comet breaking apart in real time.
During its routine imaging of the universe, the space telescope discovered an unexpected object called C/2025 K1 (ATLAS)or comet K1 for short. Remarkably, Hubble’s observations revealed that the comet’s nucleus was actively fragmentingaccording to a statement from NASA.
“Sometimes the best science happens by accident,” said John Noonan, co-author of the study and a physics professor at Auburn University. the statement. “This comet (was) observed because our original comet was not visible due to some new technical limitations after we won our proposal. We had to find a new target – and just as we observed it, it broke up, which is the slimmest chance.”
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Comets are icy, rocky objects from the outer solar system that heat up as they approach the sunreleasing gas and dust to form a glowing coma and tail. They can also break apart when solar heat and gravitational forces overwhelm their fragile structure.
Astronomers observed K1 over three consecutive days, from November 8 to November 10, 2025, and found that it had already begun to disintegrate before Hubble turned his gaze towards it. The telescope captured the comet splitting into at least four parts, each surrounded by its own coma. One fragment appeared to split again during the observations, suggesting that the process was still unfolding.
Scientists estimate that the rupture began about a week earlier, likely triggered by the comet’s close approach to the Sun, known as perihelionwhen heating and stress are at their peak.
Discovered in May 2025 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey, K1 is a distant long-period comet Oort Clouda vast reservoir of icy bodies at the edge of the solar system. These objects are considered relics of the early solar system, preserving the material largely unchanged for billions of years. Before fragmentation, K1 was probably slightly larger than an average comet, measuring about 8 kilometers across, according to the statement.
Comets such as K1 are often described as “dirty snowballs,” made of ice, dust, and rock loosely bound together. As they approach the Sun, the ice sublimates into gas, creating jets that can push outward on the core. Combined with internal weaknesses and gravitational tension, these forces can cause the comet to rupture.
But K1’s break revealed an additional mystery. Ground-based observers did not see the comet brighten immediately after it was fragmentedwhich can be expected when fresh ice is exposed. Instead, there was a delay between the breach and visible eruptions.
Scientists think this may be because a comet’s brightness comes mainly from sunlight reflecting off dust, not ice. Newly exposed ice may first need to develop a thin layer of dust that can then be blown off, or heat may need to build below the surface before releasing an expanding cloud of dust, according to the statement.
“Never before has Hubble captured a fragmenting comet so close to when it actually fell apart. Most of the time it’s a few weeks to a month later. And in this case, we were able to see it just days after,” Noonan said in the statement.
“This tells us something very important about the physics of what’s happening on the comet’s surface. We might be able to see the timescale it takes to form a significant dust layer that can then be ejected from the gas.”
Seeing a comet disintegrate in real time is extremely rare, as these events are unpredictable and often too faint to observe in detail. Hubble’s high-resolution images allowed scientists to trace the fragments as they drifted apart, giving an unusually clear overview of the process. As these fragments continue to separate and fade, K1 offers a rare and fleeting window into how some of the Solar System’s oldest objects evolve.
Their findings were published 6 Feb in the journal Ikaros.
