Posted on: Jan 8, 2006
The Hubble Space Telescope photographed a new pair of rings around Uranus and two new, small moons orbiting the planet. The largest ring is twice the diameter of the planet's previously known rings; the rings are so far from the planet that they are being called Uranus' 'second ring system.' One of the new moons shares its orbit with one of the rings. Analysis of the Hubble data also reveals the orbits of Uranus' family of inner moons have changed significantly over the past decade.
Since dust orbiting Uranus is expected to be depleted by spiraling away, the planet's rings must be continually replenished with fresh material. 'The new discoveries demonstrate that Uranus has a youthful and dynamic system of rings and moons,' said Mark Showalter of the SETI Institute, Mountainview, Calif.
Showalter and Jack Lissauer of NASA's Ames Research Center propose that the outermost ring is replenished by a 12-mile-wide newly discovered moon, named Mab, which they first observed in 2003.
Meteoroid impacts continually blast dust off the surface of Mab. The dust then spreads out into a ring around Uranus. Mab's ring receives a fresh infusion of dust from each impact. Nature keeps the ring supplied with new dust while older dust spirals away or bangs back into the moon.
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'To myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.'