Archival images snapped by the Hubble Space Telescope revealed the unusual event
| Daily Correspondent
April 2, 2026
An artist’s concept of comet 41P as it approached the sun, turning some of its ice into gaseous jets
NASA / ESA / CSA / Ralf Crawford (STScI)
Comets are unpredictable objects. Scientists struggle to forecast the paths and brightnesses of these icy space rocks. Now, an astronomer has caught something especially strange: a comet possibly flipping its rotation.
The observation was described on March 26 in the Astronomical Journal.
Nine years ago, comet 41P/Tuttle-Giacobini-Kresák—41P for short—dramatically slowed its spin. Researchers reported that in early 2017, the comet took about 46 to 60 hours to complete one rotation, more than twice as long as its previous roughly 20-hour spin.
Comets do sometimes change their rotation rates, but usually by mere minutes. “By so many hours and so drastically, that we’ve never seen,” says Dennis Bodewits, an astronomer at Auburn University and a co-author of the older study, to Jonathan O’Callaghan at the New York Times.
Comet 41P Reversal Animation – Hubble Space Telescope
It turns out that comet 41P’s rotation got even weirder after that. Recently, David Jewitt, an astronomer at the University of California, Los Angeles, analyzed archival images snapped by the Hubble Space Telescope in December 2017. At that point, the space rock’s spin had sped up again to about 14 hours per rotation, he found.
The simplest explanation for that year’s events? Comet 41P slowed its spin, came to a stop, then began to rotate in the opposite direction.
This probably happened because the sun heated some of the comet’s ice, turning it into gaseous jets that acted like thrusters on a rocket, Jewitt tells Nikk Ogasa at Science News. Most of those powerful jets are likely located on one side of the space rock, forcing it to spin in a certain direction.
“It’s like pushing a merry-go-round,” Jewitt says in a statement from NASA. “If it’s turning in one direction, and then you push against that, you can slow it and reverse it.”
The comet is considered small, as its rocky center, or nucleus, measures about 0.6 miles wide, which probably makes it somewhat easy to twist. It’s estimated to have entered its current orbit about 1,500 years ago, after being flung there via Jupiter’s gravity, and it now visits Earth’s neck of the solar system—the inner part—roughly every 5.4 years.
Need to know: What is a comet?
Comets are icy leftovers from the formation of the solar system some 4.6 billion years ago. They contain frozen gases, rock and dust because they matured far from the sun’s heat.
“Most comets of this size probably change their rotation on comparable or shorter timescales,” says Qicheng Zhang, an astronomer at the Lowell Observatory who was not involved in the study, in a statement from the observatory. “They just tend to not pass close enough to Earth for these changes to be observable. In many cases, they’re just destroyed before we ever get a second look at the rotation.”
Jane Luu, an astronomer at the University of Oslo in Norway, who was not involved in the work, tells the Times she agrees that researchers have suspected that comets undergo rotation switch-ups. “But as far as I know, this is the first observation to catch a comet doing that in the act,” she says.
While most changes to a comet’s structure take centuries, the new work suggests that the surface of comet 41P is rapidly evolving, presenting a rare opportunity to watch one of these space rocks transform on a human timescale.
Jewitt’s computer simulations of the comet suggest that its spin will continue to speed up, and the force from that motion will eventually grow stronger than the gravity keeping it together, so it’ll fragment into several pieces. While it’s hard to predict when, exactly, comet 41P will meet its demise, he tells Science News that it might happen in only a few decades.
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