Are there moonlets near the Uranian alpha and beta rings?
  The Voyager 2 Radio Science Subsystem occultations of the Uranian alpha and beta rings exhibit quasi-periodic optical depth variations with radial wavelengths that vary with longitude. These patterns may be wakes from small moonlets orbiting exterior to these rings. Based on the observed structures in the rings, we estimate that the moonlets would need to be located about 100 km exterior to the rings' semimajor axes and be 2-7 km in radius. Such moonlets could help keep the rings confined. Due to their small radii and presumed low albedo, the expected brightness of these moonlets is on the order of the noise in Voyager 2 images. 
R. O. Chancia and M. M. Hedman
astro-ph.EP