Image: Saturn's giant ring
NASA / JPL-Caltech / Keck
This artist's conception simulates an infrared view of the giant ring surrounding Saturn. The planet itself is just a tiny speck that is enlarged in the inset image. staff and news service reports
updated 10/6/2009 9:51:57 PM ET 2009-10-07T01:51:57

NASA's Spitzer Space Telescope has discovered the biggest but never-before-seen ring around the planet Saturn.

The Jet Propulsion Laboratory said Tuesday that the ring lies at the far reaches of the Saturnian system, and its orbit is tilted 27 degrees from the planet's main ring plane.

The ring is made of a tenuous array of ice and dust particles.

JPL spokeswoman Whitney Clavin said the ring is very diffuse and doesn't give off much visible light, but the infrared Spitzer telescope was able to detect it. Infrared observations are well-suited to detect the dusty, cold material in interplanetary space.

Although the ring dust is very cold — 316 degrees below zero Fahrenheit, or 80 Kelvin — it still gives off enough thermal radiation to register on Spitzer's sensors.

The bulk of the ring material starts about 3.7 million miles from the planet and extends outward about another 7.4 million miles. The ring is so huge it would take a billion Earths to fill it, JPL said.

"This is one supersized ring," said Anne Verbiscer, an astronomer at the University of Virginia at Charlottesville. "If you could see the ring, it would span the width of two full moons' worth of sky, one on either side of Saturn."

Verbiscer is one of the authors of a paper about the discovery being published online this week by the journal Nature. The other authors include Douglas Hamilton of the University of Maryland at College Park and Michael Skrutskie of the University of Virginia at Charlottesville.

Before the discovery, Saturn was known to have seven main rings named A through E and several faint unnamed rings.

Scientists said the wide ring could help solve one of the longstanding riddles of the Saturnian system. One of the planet's more than 60 moons, Iapetus, has a strange two-tone, black-and-white appearance. Hamilton noted that the newly discovered ring was circling in the same direction as another moon called Phoebe, but opposite to Iapetus and most of Saturn's other moons.

Some of the dark and dusty material from the outer ring appears to be moving inward, slamming into Iapetus like bugs on a windshield.

"Astronomers have long suspected that there is a connection between Saturn's outer moon and the dark material on Iapetus," Hamilton said in a NASA news release. "This new ring provides convincing evidence of that relationship."

The Spitzer mission, launched in 2003, is managed by JPL in Pasadena. Spitzer is 66 million miles from Earth in orbit around the sun.

More on Saturn | Spitzer Space Telescope

This report includes information from The Associated Press and NASA.

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