Rings of Uranus - A review of occultation results

The structure and orbits of the nine confirmed rings of Uranus are reviewed based on occultation observations from ring discovery in March 1977 through April 1981. Observations of stellar occultations by Uranus have revealed the rings to be characterized by narrow widths (up to 100 km) and sharp edges, with possible internal structure, and to have orbits fitting the coplanar precession model, and showing a decreasing eccentricity with semimajor axis. Occultation results have also allowed the determination of the J2 and J4 coefficients of the Uranian gravity potential, the coordinates of the ring plane pole, planetary equatorial radius and ellipticity and the rotation period. The sharp edges and narrow widths of the rings may be explained by small satellites orbiting near the rings, and the uniform precession of three of the rings is attributed to self-gravity. Future plans for Uranus ring observations include further occultation studies, the Voyager 2 fly-by, and Space Telescope data.