Astronomer Observes Comet 41P Possibly Reversing Its Rotation Direction

Astronomer David Jewitt of the University of California, Los Angeles, has analyzed Hubble Space Telescope images from December 2017 showing comet 41P/Tuttle-Giacobini-Kresák exhibiting unusual rotational behavior. The comet, which measures approximately 0.6 miles in diameter, had previously been observed slowing its spin dramatically around 2017, taking 46 to 60 hours per rotation compared to its earlier roughly 20-hour period. Jewitt's recent examination indicates the comet's rotation then accelerated to about 14 hours per revolution. The most straightforward interpretation is that the comet halted its spin entirely before beginning to rotate in the opposite direction. This phenomenon is likely caused by solar heating converting the comet's ice into gaseous jets that act like thrusters, exerting torque on the object. The findings were detailed in a study published on March 26 in the Astronomical Journal. Researchers, including Dennis Bodewits of Auburn University, note that while comets sometimes alter their rotation rates slightly, such a drastic change involving a complete reversal had not been documented before. Astronomer Jane Luu of the University of Oslo, who was not involved in the research, agrees that rotation reversals were suspected but this marks the first direct observation. The comet's small size and its estimated entry into its current orbit about 1,500 years ago, via Jupiter's gravity, make it susceptible to such changes. It orbits through the inner solar system approximately every 5.4 years. Jewitt's simulations suggest the comet's spin will continue accelerating, potentially leading to fragmentation within decades as centrifugal forces overcome its structural integrity. This observation provides a rare chance to study rapid surface evolution on a human timescale, contrasting with the typically slow changes seen in these icy solar system remnants.