Wednesday, March 31, 2010

Looking at Saturn with Voyager

The Voyager probes told us much more about the rings than we could have discovered from our earthly perspective.
First, data from Voyager confirmed that the rings are indeed made up of particles, primarily of water ice. Voyager also revealed additional rings, invisible from an earthly perspective. The F ring is more than twice the size of the A ring, stretching out to 186,000 miles.
The D ring is the innermost ring—closer to the planet than the innermost ring visible from the earth, the C ring. F and E are outside of the A ring.
But these additional rings are only part of what
Voyager told us. Voyager 2 revealed that the six major rings are composed of many thousands of individual ringlets, which astronomers liken to ripples or waves in the rings.
Voyager 2 also revealed many gaps within the rings, which are believed to be caused by small moonlets, which may be considered very large ring particles—a few miles in diameter—in orbit around Saturn. The gaps are, in effect, the wake of these bodies. Perhaps the most remarkable Voyager discovery concerning Saturn’s rings concerns the outermost F ring. Its structure is highly complex, sometimes appearing braided. Apparently, the structure of the F ring is influenced by two small outlying moons that bracket the ring called shepherd satellites, which seem to keep the F ring particles from moving in or out.

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