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Neptune Rings

Neptune has a faint planetary ring system of unknown composition. The rings have a odd "clumpy" structure, the cause of which is not currently understood but which may be due to the gravitational interaction with small moons in orbit near them.

Indication that the rings are incomplete first arose in the mid-1980s, when stellar occultation experiments were found to occasionally show an extra "blink" just before or after the planet occulted the star. Images by Voyager 2 in 1989 settled the issue, when the ring system was found to contain several faint rings, the outermost of which, Adams, contains three major arcs now named Liberté, Egalité, and Fraternité (Liberty, Equality, and Fraternity). The subsistence of arcs is very difficult to recognize because the laws of motion would forecast that arcs spread out into a uniform ring over very short timescales. The gravitational effects of Galatea, a moon just inward from the ring, are now believed to confine the arcs.

Several other rings were detected by the Voyager cameras. Besides to the narrow Adams Ring 63,000 km from the centre of Neptune, the Leverrier Ring is at 53,000 km and the broader, fainter Galle Ring is at 42,000 km. A faint apparent extension to the Leverrier Ring has been named Lassell; it is bordered at its outer edge by the Arago Ring at 57,000 kmNew Earth-based observations announced in 2005 appeared to show that Neptune's rings are much more unstable than previously thought. In selective, it seems that the Liberté ring might disappear in as little as one century. The new observations appear to throw our understanding of Neptune's rings into considerable confusion.