For the first time, an astronomer has seen a comet change its speed and direction of rotation, thanks to a new analysis. The Hubble Telescope photos. The unexpected change is caused by “outgassing” jets that shoot an icy mixture of gas and dust into the solar system, according to a new study.
Well, named 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 by the Slovak scientist L’ubor Kresák in 1951 (hence its long name). Comet 41P may come from the Kuiper Belt – a ring of stars, comets and small planets beyond the orbit of Neptune – and will likely spend most of its long life in orbit day over a period of decades to centuries.
During the 2017 flyby, astronomers noticed that 41P’s rotation rate slowed significantly as the comet shot past Earth – which scientists had previously attributed to a normal outflow event. Hubble also took many aerial photographs. However, these images were preserved and were not well studied.
Now, in a new study published on March 26 Astronomical JournalThe astronomer analyzed the Hubble images from 2017 and found that the sudden decrease was followed by an earlier unknown event.
By comparing Hubble images with data collected by ground-based telescopes, the author of the study David the JewUCLA astronomer, estimated the changes in the rotation of 41P throughout 2017. He found that in May of that year, the comet’s spin had decreased to one rotation every 46 to 60 hours, which was three times slower than it was rotating in March 2017. But in December 2017, the return from each period was returning faster than 14 hours. than previously thought, according to sister site Live Science Space.com.
But if smoking slowed the comet’s rotation, how could it speed it up again so quickly? The only thing that makes sense, Jewitt argues, is if the direction of the comet’s spin were to change completely.
“It’s like pushing a merry-go-round,” he said a statement. “If it turns to one side, and you push against it, you can slow it down and bring it back.”
With the Hubble data, Jewitt also deduced the true size of 41P’s nucleus, which is about 0.6 miles (1 kilometer) across – about three times the height of Paris’ Eiffel Tower. That might sound impressive, but it’s actually too small for a comet. And its small size may prove to be the key to explaining its unusual behavior.
Passing gas
Almost all known comets have been observed to be “outgassing” at some point in their lives. This phenomenon occurs when ice, gas and dust from the comet’s interior escapes from small cracks in its core – usually due to the increase in the sun’s distance, which allows the sun’s rays to weaken the comet’s interior and destroy its icy shell.
In recent years, we’ve seen several amazing examples of bleeding in action, including the demonic horns of the exploding devil comet 12P/Pons-Brooks, ie closed around the clock in 2024, and multiple jets and “anti-tail” of interstellar matter 3I/ATLASwhich was seen shooting across the solar system last year.
Scientists previously knew that ejecting water could change a comet’s rotation, but most of these objects are too large for an ejected jet to make a significant difference before it disappears. However, the small size of 41P may help the comet’s flight to make a big impact.
“Jets of gas flowing over water can act as micro-filters,” Jewitt said in the statement. “If those jets are distributed unevenly, they can dramatically change how a comet, especially a small one, rotates.”
Experts are not sure whether the extreme 41P bleeding event was caused by multiple jets or a single large flow. But if repeated events occur during the comet’s next perihelion, the icy ball may eventually break apart, like Comet C/2025 K1 (ATLAS), which. it mysteriously broke up in late 2025.
“I’m looking forward to this core [41P] it will kill itself quickly,” Jewitt said.
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