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Astronomers using NASA’s Hubble Space Telescope have found evidence that the spinning of a small comet, 41P/Tuttle-Giacobini-Kresák, slowed and then reversed its direction of rotation, offering a dramatic example of how volatile activity can affect the spin and physical evolution of small bodies in the solar system. This is the first time researchers have observed evidence of a comet reversing its spin.
Why it matters
The rapid rotational shifts observed in comet 41P provide a rare opportunity to witness evolutionary processes unfolding on a human timescale, as most changes in comet structure typically occur over centuries or longer. Understanding how comets’ spin and physical properties change over time can offer insights into the formation and evolution of the solar system.
The details
After 41P’s 2017 close passage around the Sun, scientists found that the comet experienced a dramatic slowdown in its rotation. Follow-up Hubble observations later that year detected the comet spinning much faster again, with a period of approximately 14 hours, compared to the 46 to 60 hours measured earlier. Researchers say the simplest explanation is that the comet continued slowing until it almost stopped, and was then forced to spin in the near-opposite direction by outgassing jets on its surface.
In March 2017, the comet was observed by the Discovery Channel Telescope at Lowell Observatory in Arizona.In May 2017, data from NASA’s Neil Gehrels Swift Observatory showed the comet was spinning three times more slowly than in March.In December 2017, Hubble images detected the comet spinning much faster again, with a period of approximately 14 hours.
The players
Comet 41P/Tuttle-Giacobini-Kresák
A tiny Jupiter-family comet that likely originated in the Kuiper Belt and is now visiting the inner solar system every 5.4 years.
David Jewitt
A paper author from the University of California at Los Angeles.
NASA’s Hubble Space Telescope
The space telescope that detected the dramatic changes in the comet’s spin.
NASA’s Neil Gehrels Swift Observatory
The observatory that provided data showing the comet’s dramatic slowdown in rotation in 2017.
Discovery Channel Telescope at Lowell Observatory
The telescope that observed the comet in March 2017.
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What they’re saying
“Jets of gas streaming off the surface can act like small thrusters. If those jets are unevenly distributed, they can dramatically change how a comet, especially a small one, rotates.”
— David Jewitt, Paper author
“It’s like pushing a merry-go-round. If it’s turning in one direction, and then you push against that, you can slow it and reverse it.”
— David Jewitt, Paper author
“I expect this nucleus will very quickly self-destruct.”
— David Jewitt, Paper author
What’s next
The study suggests that continued rotational changes could eventually lead to structural instability for comet 41P, potentially causing fragmentation or even disintegration.
The takeaway
The dramatic spin changes observed in comet 41P offer a rare glimpse into the rapid evolution of comets, providing insights into the formation and evolution of the solar system that are typically only visible over much longer timescales.