What is the name of the faint, outermost ring of Saturn?

The Phoebe ring is the faint, outermost ring of Saturn. Unlike Saturn's bright main rings, it is a vast, diffuse cloud of dust that is nearly invisible in ordinary photographs and was identified through infrared observations.

The ring was discovered in 2009 using NASA's Spitzer Space Telescope. It stretches across an enormous region, beginning near the orbit of Iapetus and extending far beyond Phoebe's orbit. Its particles follow a plane close to Saturn's orbital plane around the Sun, rather than the equatorial plane occupied by the main rings.

Scientists think impacts on Phoebe, a dark outer moon, continuously supply the ring with dust and debris. Because Phoebe travels in a retrograde orbit, the ring's particles move opposite to the direction of most of Saturn's inner moons. Radiation forces gradually push some of this material inward.

The Phoebe ring is easy to confuse with Saturn's F ring, which is the outermost discrete main ring. The F ring is much closer to Saturn and is narrow, bright, and dynamically active; the Phoebe ring is vastly larger but extremely faint.