Arcs and Clumps in the Uranian λ Ring

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Science  27 Jan 1995:
Vol. 267, Issue 5197, pp. 490-493
DOI: 10.1126/science.267.5197.490


Careful reprocessing of the Voyager images reveals that the Uranìan λ ring has marked longitudinal variations in brightness comparable in magnitude to those in Saturn's F ring and Neptune's Adams ring. The ring's variations show a dominant five-cycle (72-degree) periodicity, although additional structure down to scales of about 0.5 degree is also present. The ring's shape is defined by a small overall eccentricity plus a six-cycle (60-degree) sinusoidal variation of radial amplitude around 4 kilometers. Both of these properties can be explained by the resonant perturbations of a moon at a semimajor axis of 56,479 kilometers, but no known moon orbits at this location. Unfortunately, the mass required suggests that such a body should have been imaged by Voyager.