Which Neptune ring contains the bright arcs imaged by Voyager 2 in 1989?

The Neptune ring containing the bright arcs imaged by Voyager 2 in 1989 is the Adams ring.

Voyager 2’s Neptune flyby on August 25, 1989, settled a long-running mystery. Earth-based stellar-occultation observations had hinted that Neptune possessed incomplete rings, but the spacecraft photographed a system of faint, narrow rings and showed that the bright clumps were embedded in the outermost Adams ring.

The Adams ring contains five named arcs: Fraternité, Égalité 1, Égalité 2, Liberté, and Courage. Unlike a complete, evenly distributed ring, these arcs occupy only a limited range of orbital longitudes. Their persistence is unusual because ordinary orbital motion should gradually spread ring particles around Neptune.

The Adams ring is named for John Couch Adams, who independently predicted Neptune’s position. Its nearby shepherd moon Galatea probably helps shape the ring, although the precise mechanism that confines the arcs remains an active subject of study. The Le Verrier, Lassell, and Galle rings are separate parts of Neptune’s ring system and do not contain the famous bright arc complex.