Nasa says they have discovered an enormous ring around Saturn, which they say is "by far the largest of the planet’s many rings".

The new halo is about twenty times the diameter of the planet in height, and it would take about one billion Earths stacked together to fill the ring.

Nasa say the new belt lies at the far reaches of the Saturnian system, with an orbit tilted 27 degrees from the main ring plane. One of Saturn’s farthest moons, Phoebe, circles within the newfound ring, and is likely the source of its material.

"This is one supersized ring," said Anne Verbiscer, an astronomer at the University of Virginia, 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."

The ring was spotted using the telescope Spitzer’s infrared eyes were able to spot the glow of the band’s cool dust. The telescope, launched in 2003, is currently 107 million kilometers (66 million miles) from Earth in orbit around the sun.

Ms Verbiscer, Douglas Hamilton of the University of Maryland, College Park and Michael Skrutskie, of the University of Virginia, Charlottesville, are authors of a paper about the discovery to be published online tomorrow by the journal Nature.

Nasa said the discovery could help to solve an age-old riddle of one of Saturn’s moons, lapetus, which has one bright side and one dark, called Cassini Regoio. The new ring could explain how Cassini Regio came to be,

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

Ms Verbiscer and her colleagues used Spitzer’s longer-wavelength infrared camera, called the multiband imaging photometer, to scan through a patch of sky far from Saturn and a bit inside Phoebe’s orbit.

Nasa said: "The astronomers had a hunch that Phoebe might be circling around in a belt of dust kicked up from its minor collisions with comets — a process similar to that around stars with dusty disks of planetary debris.

"Sure enough, when the scientists took a first look at their Spitzer data, a band of dust jumped out."

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