Largest ring in solar system found around Saturn

A colossal ring of debris found around Saturn is the largest in the solar system. The new ring could be the 'smoking gun' that explains the curious two-faced appearance of Saturn's moon Iapetus, whose leading hemisphere is much darker than its trailing side.

Until now, the biggest known rings in the solar system were Saturn's E ring and faint, gossamer sheets of dust orbiting Jupiter. Saturn's E ring, a diffuse disc of icy material fed by the moon Enceladus, extends from 3 to perhaps 20 times the radius of Saturn.

The newly discovered ring spans from 128 to 207 times the radius of Saturn – or farther – and is 2.4 million kilometres thick. It was found using NASA's Spitzer Space Telescope, which revealed an infrared glow thought to come from sun-warmed dust in a tenuous ring.

The discovery was announced on Tuesday at a meeting of the American Astronomical Society's Division of Planetary Sciences in Fajardo, Puerto Rico. "This is a unique planetary ring system, because it's the largest planetary ring in the solar system," team leader Anne Verbiscer of the University of Virginia in Charlottesville told the meeting.

The source of the ring's material seems to be Saturn's far-flung moon Phoebe, which orbits the planet at an average distance of 215 times the radius of Saturn. When Phoebe is hit by wayward space rocks, the impacts could generate debris that fills the rings.

source : NewScientist