Scientists have spotted a huge ring around Saturn -- the largest planetary ring seen yet in the solar system.

The faint ring, made of tiny particles, partly marks the orbit of Saturn's distant moon Phoebe, Anne Verbiscer of the University of Virginia and colleagues reported on Wednesday in the journal Nature.

Phoebe, orbits the giant planet at a radius of about 8 million miles (13 million kilometres) and, evidently, objects colliding with Phoebe and kicking up dust keep the ring supplied with material.

"The closest analogs to the Phoebe ring are the two gossamer rings associated with Jupiter's inner satellites, Thebe and Amalthea," they wrote. These moons, too, are the source of dust kicked up by collisions.

"Similar structures should also adorn the other gas giant planets," the researchers added.