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Science 27 January 1995:
Vol. 267. no. 5197, pp. 490 - 493
DOI: 10.1126/science.267.5197.490
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Articles

Arcs and Clumps in the Uranian lgr Ring

Mark R. Showalter 1

1 Center for Radar Astronomy, Stanford University, Stanford, CA 94305, USA.

Careful reprocessing of the Voyager images reveals that the Uranìan lgr 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.

Submitted on July 26, 1994
Accepted on October 25, 1994

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Science. ISSN 0036-8075 (print), 1095-9203 (online)