Farting comet seen reversing its spin for the first time ever and may soon self-destruct, Hubble photos reveal
For the first time, an astronomer has observed a comet change the speed and direction of its own rotation, thanks to new analyses. Hubble Space Telescope photos. This unexpected reversal was triggered by “outgassing” jets that sprayed an icy mixture of gas and dust into the solar system, a new study suggests.
The comet, nicknamed 41P Tuttle-Giacobini-Kresák (41P for short), was discovered by the American astronomer Horace Parnell Tuttle in 1858, before being rediscovered by the French astronomer Michel Giacobini in 1907 and again by the Slovak scientist L’ubor Kresák in 1951 (hence its long name). Comet 41P likely originates from the Kuiper Belt – the ring of asteroids, comets and dwarf planets beyond the orbit of Neptune – and probably spent most of his long life going around in circles the sun over a time scale ranging from several decades to several centuries.
During the 2017 flyby, astronomers noticed that 41P’s rotation rate slowed significantly as the comet passed in front of Earth – which scientists had previously attributed to a standard outgassing event. Hubble also took numerous photos of the flyby. However, these images have been classified and have not been studied properly.
However, in the new study published on March 26 in The astronomical journalan astronomer analyzed Hubble images from 2017 and found that the sudden slowdown was followed by a previously little-known acceleration event.
By comparing Hubble images to data collected by ground-based telescopes, the study author David Jewitta UCLA astronomer, estimated changes in 41P’s rotation throughout 2017. He found that by May of that year, the comet’s rotation had slowed to about one rotation every 46 to 60 hours, about three times slower than in March 2017. But by December 2017, the comet was rotating every 14 hours, representing a return to form much faster than expected, according to the Live Science partner site Espace.com.
But if the outgassing had slowed the comet’s rotation, how could it have accelerated it again so quickly? According to Jewitt, the only thing that would make sense would be if the comet’s direction of rotation was completely reversed.
“It’s like pushing a merry-go-round,” he said in a statement. “If it turns in one direction and you push against that direction, you can slow it down and reverse it.”
With the Hubble data, Jewitt also constrained the actual size of 41P’s core, which is about 1 kilometer in diameter, or about three times as wide as the Eiffel Tower in Paris. This may sound impressive, but it’s actually quite small for a comet. And its small size could prove key to explaining its unusual behavior.
Gas passage
Almost every known comet has been observed “outgassing” at some point in its life. This phenomenon occurs when ice, gas and dust from the comet’s interior burst out of small cracks that appear in its core – normally due to increased proximity to the sun, which allows solar radiation to sublimate the comet’s innards and crack its icy shell.
In recent years we have seen several amazing examples of outgassing in action, including the demonic horns of the explosive “devil’s comet” 12P/Pons-Brooks, which slingshot around the sun in 2024, and the multiple jets and “anti-tail” of the interstellar object 3I/ATLASwho was spotted shoot across the solar system last year.
Scientists previously knew that outgassing could change a comet’s rotation, but most of these objects are too large for an outgoing jet to make much of a difference before it disappears. However, 41P’s relatively small size likely allowed the comet’s jets to have a greater impact.
“Gas jets flowing from the surface can act as small thrusters,” Jewitt said in the release. “If these jets are unevenly distributed, they can dramatically change the way a comet, especially a small one, spins.”
Experts are unsure whether the extreme outgassing of 41P was caused by multiple jets or a single massive flow. But if repeated events occur during the comet’s next perihelions, the ice ball could end up tearing apart, like comet C/2025 K1 (ATLAS), which collapsed spectacularly at the end of 2025.
“I’m waiting for this core [41P] will self-destruct very quickly,” Jewitt said.
