Uranus' ringsA system of planetary rings. The first six were discovered in 1977 when the planet occulted a star. Three further rings were found by Perth observatory, and Voyager 2 discovered two more rings in 1986. The 11 rings are narrow and dark, unlike Saturn's, which are broad and bright (see table). Most of them are less than 10 km wide and typical particles within them can be compared with large lumps of coal roughly 1 m in size. The Uranian rings have a low albedo of about 0.01. The most prominent, the Epsilon ring, is gray in color and has segments that are nearly 100 km wide. All the rings are well within the Roche limit. Voyager 2 found only two shepherd satellites – Cordelia and Ophelia, which together control the Epsilon ring –although the rings are confined to very narrow orbits.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006