Blue, Blue, Its Ring Is Blue

Scientists reporting in the April 7 issue of Science have discovered that the outermost ring of Uranus, discovered just last year, is bright blue, making it only the second known blue ring in the solar system, the first being that of Saturn. Interestingly, both blue rings are associated with small moons; Enceladus orbits within Saturn’s blue ring and Uranus’s recently discovered Mab orbits within the seventh planet’s blue ring. Another interesting fact surrounds the blue color of the rings. All other rings in the solar system - those around Jupiter, Saturn, Uranus, and Neptune - are reddish in color primarily because the particles comprising them are large and preferentially scatter and reflect red light. The particles in the blue rings of Uranus and Saturn are sub-micron (less than a thousanth the width of a human hair) that scatter and reflect mostly blue light. Check out the UCBerkeley press release and Dr. Imke de Pater’s "One Ring, Two Ring, Red Ring, Blue Ring" web page for more fascinating information on this colorful discovery.