The Uranian Rings
Voyager 2 also expanded the body of information pertaining to the rings and moons of Uranus. Voyager's cameras obtained the first images of 9 previously known narrow rings and discovered at least 2 new rings, one narrow and one broadly diffused, bringing the total known rings to 11. It was found that a highly structured distribution of fine dust exists throughout the ring system.
The outermost (epsilon) ring contains nothing smaller than fist-sized particles. It is flanked by two small moons discovered interior to the orbit of the Uranian moon Miranda. The moons exert a shepherding influence on the epsilon ring and on the outer edges of the gamma and delta rings.
All of the rings lie within one planetary radius1 of Uranus's cloud tops. Most of Uranus's rings are narrow, ranging in width from 0.6 to 58 mi (1 to 93 km), and are only a few kilometers thick. The Uranian rings are colorless and extremely dark. The dark material may be either irradiated methane ice or organic-rich minerals mixed with water-impregnated, silicon-based compounds. There is evidence that incomplete rings, or “ring arcs,” exist at Uranus.
1. The equatorial radius of Uranus is 15,880 mi (25,560 km) at a pressure of 1 bar.