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Resonantly-generated patterns in the Uranian Rings

Presentation #112.01 in the session Many Planets, More Rings (Oral Presentation)

Published onOct 23, 2023
Resonantly-generated patterns in the Uranian Rings

Uranus is surrounded by nine exceptionally narrow rings, and four of these rings fall close enough to mean motion resonances with three of Uranus’ small satellites (Cressida, Ophelia and Cordelia) for those resonances to have a detectable affect on the rings’ mean position and/or width. These perturbations can be detected as variations in ring positions in occultations and brightness variations in images. Measurements of the edge position variations derived from the occultation data already provided estimates of the masses of Cressida (Chancia et al. 2017 AJ), and now yield information about the masses of Cordelia and Ophelia (French et al. in prep.). All three masses are consistent with these moons having mass densities comparable to the critical density required for a strengthless moon to avoid being disrupted by tidal forces (Tiscareno et al. 2013 ApJ). Meanwhile, the images show that the resonantly-induced brightness variations vary systematically depending on the phase of the longer-wavelength normal-modes in these rings, and in some cases the fractional brightness variations are bigger than the fractional variations in the rings’ widths. These findings could provide new insights into the rings’ internal dynamics and how they might be confined.

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