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A simple numerical model of tidal despinning for Hi’iaka

A simple numerical model of tidal despinning for Hi’iaka
A simple numerical model of tidal despinning for Hi’iaka The black line shows the orbital period and how it grows as a function of time (plotted on the x-axis logarithmically). The colored lines show 9 different initial spin rates for Hi’iaka, from 1 (purple) to 100 (red) hours. (Note that the red and orange lines should be dashed: they are showing spin periods. The nature of despinning tides (in our basic model) is that they always move Hi’iaka towards synchronous rotation, when the spin and orbital periods are the same (e.g., the colored lines on top of the black line). Starting with a very fast rotation (cool colors), despinning tides can barely slow Hi’iaka down over the age of the solar system, allowing the rapid rotation seen today. But even if Hi’iaka starts near synchronous (yellow 20 hours period), the rapid expansion of orbital period initially outstrips the tidal despinning. Danielle Hastings (UCLA)