A comet has left scientists amazed by doing something unexpected. In early 2017, comet 41P/Tuttle-Giacobini-Kresák had a close encounter with the Sun. During this time, its spin seemed to slow down and then even reversed direction. This strange behavior surprised astronomer David Jewitt from UCLA.
While changes in a comet’s spin when near the Sun aren’t unheard of, the speed and scale of this reversal are unique. Jewitt noted that 41P’s spin slowed dramatically—over ten times faster than the previous record holder, 103P/Hartley 2, which took 90 days for its slowdown.
To understand this, let’s look at what happened with 41P. In March 2017, its rotation period was about 20 hours. By May, it had slowed to roughly 53 hours. Then, by December, it spun even faster—about 14.4 hours per rotation. Jewitt thinks the rotation actually stopped for a while before reversing.
The science behind this is fascinating. Comets are basically clumps of rock and ice. As they approach the Sun, heat causes some of the ice to turn directly into gas, a process known as sublimation. This creates jets that shoot gas into space, causing the comet to spin in unexpected ways. Smaller comets, like 41P, are more affected by these gas jets than larger ones.
Jewitt explained that uneven heating from the Sun, or an uneven distribution of ice in the comet, could easily account for the rapid reversal in spin. Observations show that, while we can track the spin rate, we can’t directly determine its direction. Jewitt pieced the information together using data from the Hubble Space Telescope, concluding that the spin likely slowed to a stop before flipping.
Interestingly, if 41P continues to change its spin at this rate, it might break apart in the coming decades. Yet, we haven’t measured its spin rate since September 2022. We’ll have to wait until its next close approach in 2028 for more data.
Comets offer a glimpse into the early Solar System. Though delicate, they have survived for about 4.5 billion years. The unusual changes in 41P suggest it might be a remnant of a larger comet that has gradually lost mass over time. For more on this topic, you can check the findings published on arXiv.
As science continues to uncover the mysteries of comets, researchers learn more about the dynamics of our Solar System. Each discovery helps us connect the past with present events, providing valuable insights into the universe we inhabit.
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