Free Astronomy Magazine May-June 2026

MAY-JUNE 2026 ASTRO PUBLISHING of Physics at Auburn University in Alabama in the United States. “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.” Noonan didn’t know K1 was fragmenting until he viewed the images the day after Hubble took them. “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.” This is an experiment the researchers always wanted to do with Hubble. They had proposed many Hubble observations to catch a comet breaking up. Unfortunately, these are very diffi- cult to schedule, and they were never successful. “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,” explained 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 that we always have is, ‘Is this a primi- tive property or is this due to evolution?’ By cracking open a comet, you can see the ancient material that has not been processed.” Hubble caught K1 fragmenting into at least four pieces, each with a distinct coma, the fuzzy en- velope of gas and dust that surrounds a comet’s icy nucleus. Hubble cleanly resolved the frag- ments, but to ground-based telescopes, at they time they only appeared as barely distinguish- T his series of Hubble Space Telescope images of the fragmenting comet C/2025 K1 (ATLAS), or K1 for short, was taken over the course of three consecutive days: November 8, 9, and 10, 2025. Captured by Hubble’s STIS (Space Telescope Imaging Spectrograph) instrument, the sequence shows the progressive disintegration of the com- et over this brief period. This is the first time Hub- ble has witnessed a comet so early in the process of breaking up. [NASA, ESA, D. Bodewits (Au- burn). Image processing: J. DePasquale (STScI)]