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Uranus Photos Show Wild Side ; Two More Rings, Moons Found

Posted on: Tuesday, 27 December 2005, 15:00 CST

By LISA M. KRIEGER, Knight Ridder Newspapers

SAN JOSE, Calif. - A new discovery by Mountain View, Calif., scientists is improving the image of the distant blue-green planet Uranus - transforming it from a dull and dowdy place to a spot of high drama and rapid change.

NASA's Hubble Space Telescope has captured photographs of two new rings and two new moons around the seventh planet from the sun, the researchers report in Friday's issue of the online version of the journal Science.

What is most exciting is not merely the discovery of this newfound ring-moon system - but data that reveal its erratic and evolving behavior, showing that not all is serene in our solar system, the team said at a Thursday press briefing.

"It is more evidence that our solar system is a dynamic place, somewhere very active," said Mark Showalter of the Center for Search for Extraterrestrial Intelligence Research, who teamed up with Jack Lissauer of NASA-Ames Research on the project. "By watching the processes while they are occurring" on Uranus, "we can better understand the growth rate of planets."

Over the years, Uranus has gained a reputation as one of the less interesting planets in the solar system. That is because astronomers' last good look in 1986, from Voyager 2, was during its 21-year-long winter, when it resembled a bland ball.

New higher-resolution photographs shot in 2003 from the Hubble telescope, recently upgraded with better equipment, tell a different and more detailed story.

The moons and rings create a chaotic and densely packed place, with lots of gravitational jiggling, altered orbits and spinning dust, the photographs reveal.

For instance, scientists know that its moon orbits have changed measurably in the past two decades - a blink of an eye in the 4.5 billion-year life span of the solar system.

The composition of the rings is also telling. One of the rings is thought to have originated from a ruptured moon; the other ring is likely to be constantly replenished by loose dust, probably resulting from a moon's collisions with asteroids.

"Uranus is one of the most chaotic and disruptive systems in the solar system," Showalter said.

The new moons, named Cupid and Mab after Shakespearean characters, bring the number of moons circling Uranus to 27 - the most of any planet.

Uranus now has a total of 13 rings.

Source: Record, The; Bergen County, N.J.

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