Comet 41P Spin Reversal: Gas Jets May Lead to Its Destruction

Astronomers have identified the first observed instance of a comet reversing its spin, a discovery that provides insight into how volatile activity influences the physical evolution of small bodies within the solar system. The findings, detailed in a paper published in the April 2026 edition of The Astronomical Journal, center on comet 41P/Tuttle-Giacobini-Kresák.

The phenomenon was identified through a new analysis of archival images from NASA’s Hubble Space Telescope. Researchers found that the small, Jupiter-family comet experienced a dramatic shift in its rotation during its 2017 passage through the inner solar system.

The Mechanics of Spin Reversal

The reversal was triggered by outgassing jets, which occur when frozen gases on the comet’s surface sublimate as the object approaches the Sun. These jets shoot a mixture of gas and dust into space, creating a force that can act against the comet’s existing rotation.

According to the study, the simplest explanation is that these jets forced the comet’s rotation to slow down until it almost stopped, and then pushed it to spin in the opposite direction.

The timeline of the rotation change was tracked using multiple observatories. In March 2017, the Discovery Channel Telescope at Lowell Observatory in Arizona observed the comet’s initial spin. By May 2017, data from NASA’s Neil Gehrels Swift Observatory indicated that the object was spinning three times more slowly than it had in March, with a rotation period measured between 46 and 60 hours.

Hubble images from December 2017 revealed that the spin had shifted again. The comet was detected spinning much faster, with a period of approximately 14 hours, indicating that the rotation had not only reversed but was accelerating in the new direction.

The “Death Spiral” and Comet Scarcity

The acceleration of the comet’s spin may lead to its eventual destruction. Astronomer David Jewitt of the University of California, Los Angeles, suggests that the comet may continue to spin faster in this new direction until it physically tears itself apart.

This process helps explain a broader astronomical observation regarding the scarcity of small comets. Comets that are less than a kilometer wide are relatively rare because they can spin up so quickly that they are destroyed in a relatively short amount of time.

Origin and Trajectory of Comet 41P

Comet 41P/Tuttle-Giacobini-Kresák likely originated in the Kuiper Belt, the region of dwarf planets, comets, and asteroids beyond the orbit of Neptune. It spent much of its existence orbiting the sun on a timescale of centuries or decades before its trajectory was altered.

Approximately 1,500 years ago, the comet was tugged off its original course due to a close interaction with Jupiter’s gravity. This encounter placed it on its current path, which brings it into the inner solar system every 5.4 years.

The comet’s long history of discovery reflects the contributions of multiple astronomers:

• American astronomer Horace Parnell Tuttle first discovered the comet in 1858.
• French astronomer Michel Giacobini rediscovered it in 1907.
• Slovak scientist L’ubor Kresák rediscovered it again in 1951.

The observation of comet 41P’s rotational flip represents the quickest shift in a comet’s spin ever observed, providing a rare example of how outgassing can fundamentally alter the physical state of a celestial body.