Giant ring discovered around Saturn

The discovery of the Phoebe ring of Saturn, hundreds of times larger than the planet’s diameter is announced.

This ring is tilted 27 degrees from Saturn’s equatorial plane (and the other rings). It extends from 128 to 207 times the radius of Saturn; Phoebe orbits the planet at an average distance of 215 Saturn radii. The ring is about 20 times as thick as the diameter of the planet.

Since the ring’s particles are presumed to have originated from micrometeoroid impacts on Phoebe, they should share its retrograde revolution, which is opposite to the orbital motion of the next inner moon, Iapetus. Inwardly migrating ring material would thus strike the latter’s leading hemisphere, possibly causing the two-tone coloration of that moon.

Although very large, the ring is virtually invisible, it was discovered using NASA’s infra-red Spitzer Space Telescope. The existence of the ring was proposed in the 1970s by Joseph Burns of Cornell University. The discovery was made by Anne J. Verbiscer and Michael F. Skrutskie (of the University of Virginia) and Douglas P. Hamilton (of the University of Maryland, College Park) and published in Nature.

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