Scientists recently observed an amazing event involving Comet 41P. This small comet stopped spinning and then began to rotate again, but in the opposite direction. This surprising change could help us understand more about how comets behave and why some of them break apart.
The Hubble Space Telescope has been crucial in tracking Comet 41P’s brightness changes over time. Dr. David Jewitt from UCLA used past images to create a sort of clock that revealed the comet’s rotation period. In December, he calculated it took about 14.4 hours for the comet to complete one spin. However, by early June 2017, this spin came to a halt.
Ground-based telescopes also reported some staggering changes. The comet’s rotation time increased dramatically—from 20 hours in March to over 46 hours by May. This was more than ten times the typical slowdown observed in other comets. In comparison, another comet previously took around 90 days to increase from 17 to 19 hours.
Dr. Jewitt mentioned that it’s not unusual for a comet’s rotation to shift, but the extent of this slowdown is puzzling.
At just about 0.6 miles wide, Comet 41P’s small size means it responds quickly to changes. When gas jets erupt from its surface, they exert a twisting force that can alter its spin speed. This sensitivity makes it possible for small comets to either calm down or fall apart.
Sunlight plays a key role here. As the comet approaches the sun, its surface warms, turning ice directly into gas, a process called sublimation. This gas forms jets that can change the comet’s rotation. Unlike solid asteroids, loosely packed comets can exhibit rapid changes in their spinning speed.
Active jets on Comet 41P aren’t evenly distributed. This means that some jets push more forcefully, impacting how the comet spins. When sunlight hits different areas, it can turn some jets on and off, complicating predictions about its rotation.
If a comet spins too quickly, it risks breaking apart. The faster it rotates, the stronger the outward force on its surface material, which can lead to instability. Dr. Jewitt’s research suggests that if current conditions continue, Comet 41P might fracture within a few decades.
Interestingly, the comet’s surface has likely changed after multiple trips close to the sun, creating a tougher outer layer that impacts how gas escapes. This might explain a reduced ability to vent gas strongly compared to earlier returns. In fact, some researchers propose that Comet 41P could be a fragment of a larger parent comet that broke apart.
The comet will make another close approach to the sun in 2028, which will be a crucial time for researchers. They plan to observe whether the strange spinning behavior continues. This event, known as perihelion, is when the comet gets closest to the sun, making its jets most active.
Dr. Jewitt believes that small comets like 41P could vanish long before scientists have a chance to study them in depth. This raises intriguing questions about how many comets might quietly disintegrate while remaining unnoticed.
The study sheds light on a complex interplay between a comet’s size, its spin, and the forces acting upon it. As Comet 41P returns, we may learn more about its behavior and whether it’s heading toward breakup or stabilizing.
For more academic insights, see the publication in The Astronomical Journal here.
