A rapid decrease in the rotation rate of comet 41P/Tuttle-Giacobini-Kresák

Abstract

Cometary outgassing can produce torques that change the spin state of the nucleus, influencing the evolution and lifetimes of comets (1,2). If these torques spin up the rotation to the point that centripetal forces exceed the material strength of the nucleus, the comet may fragment (3). Torques that slow down the rotation can cause the spin state to become unstable, but if the torques persist, the nucleus may eventually reorient itself and start to spin up again (4). Simulations predict that most comets will go through a short phase of changing spin states, after which changes occur gradually over long times (5). We report on observations of comet 41P/Tuttle-Giacobini-Kresák during its highly favourable close approach to Earth (0.142 au on April 1, 2017) that reveal a dramatic spin-down. Between March and May 2017, the nucleus' apparent rotation period increased from 20 hours to over 46 hours, reflecting a rate of change more than an order of magnitude larger than has ever been measured before. This phenomenon must be caused by a fortuitous alignment of the comet's gas emission in such a way as to produce an anomalously strong torque that is slowing the nucleus' spin rate. The behaviour of 41P suggests that it is in a distinct evolutionary state and that its rotation may be approaching the point of instability.

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• Rapid variations of dust colour in comet 41P/Tuttle-Giacobini-Kresák
• Constraining models of activity on comet 67P/Churyumov-Gerasimenko with Rosetta trajectory, rotation, and water production measurements
• The Sublimative Torques of Jupiter Family Comets and Mass Wasting Events on Their Nuclei
• Sodium Brightening of (3200) Phaethon Near Perihelion
• Systematics and Consequences of Comet Nucleus Outgassing Torques
• Constraints on the Spin-Pole Orientation, Jet Morphology and Rotation of Interstellar Comet 2I/Borisov with Deep HST Imaging
• First Results from TESS Observations of Comet 46P/Wirtanen
• Implications of the Small Spin Changes Measured for Large Jupiter-Family Comet Nuclei
• Gas Jet Morphology and the Very Rapidly Increasing Rotation Period of Comet 41P/Tuttle-Giacobini-Kresak
• Further investigation of changes in cometary rotation
• Dust modelling and a dynamical study of comet 41P/Tuttle-Giacobini-Kresak during its 2017 perihelion passage
• Perihelion Asymmetry in the Water Production Rate of the Interstellar Object 3I/ATLAS
• Mt. Wendelstein imaging of comet 41P/Tuttle-Giacobini-Kresak during the 2017 perihelion arc
• Fitting the Light Curve of 1I/`Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques