Science News

from research organizations

NASA’s Hubble accidentally caught a comet breaking apart in real time

Date:

March 21, 2026

Source:

NASA’s Goddard Space Flight Center

Summary:

In an incredibly lucky cosmic accident, NASA’s Hubble Space Telescope captured a comet breaking apart in real time—something astronomers have long tried and failed to observe. The comet, C/2025 K1 (ATLAS), wasn’t even the original target, but when researchers pivoted to it, they unknowingly caught it mid-disintegration into multiple pieces.

Facebook

Twitter

FULL STORY

Captured by Hubble’s STIS (Space Telescope Imaging Spectrograph) instrument, this image shows the disintegration of comet C/2025 K1 (ATLAS). This is the first time Hubble has witnessed a comet so early in the process of breaking up. Hubble caught K1 fragmenting into at least four pieces, each with a distinct coma, the fuzzy envelope of gas and dust that surrounds a comet’s icy nucleus. Hubble cleanly resolved the fragments, but from the ground, they only appeared as barely distinguishable blobs. Credit: NASA, ESA, D. Bodewits (Auburn). Image processing: J. DePasquale (STScI)

In a remarkable stroke of luck, NASA's Hubble Space Telescope observed a comet in the middle of breaking apart. The odds of witnessing such an event at exactly the right moment are extremely low. The findings were published in the journal Icarus.

The comet K1, formally known as C/2025 K1 (ATLAS) -- not to be confused with interstellar comet 3I/ATLAS -- was not the intended focus of the Hubble observations.

"Sometimes the best science happens by accident," said co-investigator John Noonan, a research professor in the Department of Physics at Auburn University in Alabama. "This comet got observed because our original comet was not viewable due to some new technical constraints after we won our proposal. We had to find a new target -- and right when we observed it, it happened to break apart, which is the slimmest of slim chances."

A Surprise Discovery in Hubble Data

Noonan did not realize the comet was breaking up until he reviewed the images the following day. "While I was taking an initial look at the data, I saw that there were four comets in those images when we only proposed to look at one," said Noonan. "So we knew this was something really, really special."

Capturing a comet in the act of fragmenting is something the team had long hoped to achieve. They had submitted multiple proposals to observe such an event with Hubble, but timing these observations has proven extremely difficult, and previous attempts had not succeeded.

"The irony is now we're just studying a regular comet and it crumbles in front of our eyes," said principal investigator Dennis Bodewits, also a professor in Auburn University's Department of Physics.

"Comets are leftovers of the era of solar system formation, so they're made of 'old stuff' -- the primordial materials that made our solar system," said Bodewits. "But they are not pristine -- they've been heated; they've been irradiated by the Sun and by cosmic rays. So, when looking at a comet's composition, the question we always have is, 'Is this a primitive property or is this due to evolution?' By cracking open a comet, you can see the ancient material that has not been processed."

Hubble Reveals Comet K1 Splitting Into Pieces

Hubble observed K1 breaking into at least four separate fragments, each surrounded by its own coma, the cloud of gas and dust that forms around a comet's icy core. While Hubble clearly resolved these pieces, ground-based telescopes could only detect them as faint, barely separated points of light.

The images were taken about a month after the comet's closest approach to the Sun, known as perihelion. At that point, K1 had traveled inside Mercury's orbit, roughly one-third of the distance between Earth and the Sun. This is when comets experience the most intense heat and stress. Many long-period comets, including K1, tend to begin breaking apart shortly after this phase.

Timing the Breakup and Tracking the Fragments

Before it began to disintegrate, K1 was likely slightly larger than a typical comet, measuring about 5 miles across. Researchers estimate the breakup started around eight days before Hubble captured it. The telescope recorded three 20-second images taken on consecutive days from Nov. 8 through Nov. 10, 2025. During that short window, one of the smaller fragments also split further.

Thanks to Hubble's high resolution, scientists were able to trace the fragments backward to their original state as a single object. This allowed them to reconstruct the sequence of events. However, their analysis revealed an unexpected puzzle. Why was there a delay between the breakup and the bright outbursts later seen from Earth? If fresh ice was exposed, why did the comet not brighten right away?

A New Mystery About Comet Brightness

The team has proposed several possible explanations. A c