U-Va., U-Md. Astronomers Find Saturn Ring

By Martin Weil
Washington Post Staff Writer
Sunday, October 25, 2009

Three astronomers from the Washington region, following in the footsteps of no less illustrious a predecessor than Galileo, have discovered a new ring around the planet Saturn.

Of all the features of the solar system, few exert a greater hold on the imagination than Saturn's rings. The image of the remote planet, surrounded by rings, has often stood as a symbol of astronomy and other sciences.

The announcement of the discovery not only made known a new feature of the solar system but it also demonstrated that despite years of effort, much about the planets remains unknown.

In the announcement, published online Oct. 7 by Nature, the international weekly journal of science, Anne J. Verbiscer and Michael F. Skrutskie, both of the University of Virginia, and Douglas P. Hamilton of the University of Maryland indicated that they have apparently found the largest of the rings.

"Here we report that Saturn has an enormous ring associated with its outer moon Phoebe," the scientists said in the online report. The ring is so large, Hamilton said in an interview, that if we could look up and see it, it would occupy a place in the sky four times the size of the full moon.

The newfound rings appears to be the outermost. "There can't be anything much farther out," Hamilton said.

Made of a fine mist of tiny dark particles, the newfound ring reflects so little visible light that it has never been seen with the naked eye, astronomers say -- or, for that matter, with an optical telescope, which depends on visible light. ( It was the inner, and brighter, ring structure that was first seen through Galileo's telescope.)

To find the new ring, the astronomers searched for its infrared radiation with equipment onboard the orbiting Spitzer space telescope.

Aside from offering an expanded view of celestial wonders, the discovery helped answer two specific questions for astronomers.

It supports the idea that planetary rings -- planets other than Saturn have them -- might also be found far from planets as well as close to them.

It also gives an idea of why one of Saturn's moons, Iapetus, has both bright and dark faces. Dark particles from the newfound ring, apparently pepper one face "like bugs on a windshield," Hamilton said. This had been the theory. Now, he said, "we have hard evidence."

Hamilton said the three astronomers, Verbiscer, Skrutskie and himself, had been graduate students together at Cornell University.

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