Saturn's ring names

Updated October 19, 2026 · 5 min read

Saturn's rings are named with letters in the order they were discovered: A, B, C, D, E, F and G. Moving outward from the planet, the actual sequence is D, C, B, A, F, G and then E. The A, B and C rings are visible from Earth; the fainter ones were mostly found between 1966 and 1980 through edge-on observations or by spacecraft.

Table of Saturn's rings

Distances are measured from Saturn's center (equatorial radius 60,268 km). Boundaries are rounded: some ring edges shift by a few to tens of kilometers.

The rings one by one

D ring

The innermost ring is so faint it cannot be seen from Earth. French astronomer Pierre Guérin reported a ring inside the C ring from Pic du Midi Observatory in 1969; that signal was never confirmed, but Voyager did find a real D ring in 1980. Cassini later saw corrugations in it, probably left by a cloud of comet debris striking it in 1983.

C ring

Nicknamed the "crepe ring" for its gauzy look, the C ring was discovered in 1850 by William Cranch Bond and his son George at Harvard and almost simultaneously by William Rutter Dawes in England. It is dark and translucent enough to see Saturn's globe through. Waves in it, excited by oscillations inside the planet, have been used to probe Saturn's interior and measure its rotation period.

B ring

The giant of the system: the widest of the main rings, the most massive and the brightest. Parts of it are so dense they block almost all the light of a star passing behind. This is where the spokes appear. Its outer edge is locked by a resonance with the moon Mimas.

Cassini Division

This dark, 4,600 km band separates the B and A rings. It is not empty: it holds low-density ringlets. See Cassini Division and other gaps.

A ring

The outermost bright ring contains two clean gaps: the Encke Gap, held open by Pan, and the Keeler Gap, maintained by Daphnis. It also carries hundreds of density waves raised by nearby moons.

F ring

Discovered by Pioneer 11 in 1979, this narrow ring is probably the most dynamic in the system. It shows twists, knots and streamers that change within hours under the influence of the shepherd moons Prometheus and Pandora.

G ring

Lying well outside the main rings, the G ring is mostly dust. Cassini found a bright arc in it, trapped by a resonance with the tiny moon Aegaeon, which probably feeds the ring.

E ring

The broadest classic ring encloses the orbits of Mimas, Enceladus, Tethys and Dione. Walter Feibelman spotted it in 1966 on images taken while the rings were edge-on. Its material comes from the geysers of Enceladus: its density peaks right at that moon's orbit, about 238,000 km from Saturn.

Arcs, ringlets and minor rings

Cassini added several faint rings tied to small moons: a dusty ring along the orbits of Janus and Epimetheus, a ring along Pallene's orbit, and partial arcs accompanying Methone and Anthe, the Alkyonides. Far beyond, the Phoebe ring dwarfs everything else but shows up only in infrared light.

Inside the main rings, the International Astronomical Union has named gaps and ringlets after astronomers connected with Saturn: the Colombo Gap and Titan Ringlet in the C ring, the Maxwell Gap, the Huygens Gap at the inner edge of the Cassini Division, the Laplace and Herschel gaps, and the Encke and Keeler gaps in the A ring. For the people behind these names, see the history of Saturn observation.

Why such a confusing order?

The letters record history, not geometry. A and B were the two bright parts on either side of the Cassini Division; C was added inside them in 1850. Later discoveries simply took the next free letter: D for the ring proposed inside in 1969, E for the diffuse outer ring, then F and G from spacecraft. Rather than rename everything, astronomers kept the system, hence D, C, B, A, F, G, E.

Sources

• NASA Science, Saturn
• IAU, Gazetteer of Planetary Nomenclature (USGS)
• L. W. Esposito, Planetary Rings, Cambridge University Press, 2014
• M. M. Hedman et al., "The source of Saturn's G ring," Science, 2007