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 \sim 100 km exterior to the rings ’ semimajor axes ( 106 ^ { +22 } _ { -12 } km for \alpha and 77 ^ { +8 } _ { -4 } km for \beta ) 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 .