Rings of Neptune - Adams Ring

Adams Ring

The outer Adams ring, with an orbital radius of about 63,930 km, is the best studied of Neptune's rings. It is named after John Couch Adams, who predicted the position of Neptune independently of Le Verrier. This ring is narrow, slightly eccentric and inclined, with total width of about 35 km (15–50 km), and its normal optical depth is around 0.011 ± 0.003 outside the arcs, which corresponds to the equivalent depth of about 0.4 km. The fraction of dust in this ring is from 20% to 40%—lower than in other narrow rings. Neptune's small moon Galatea, which orbits just inside of the Adams ring at 61,953 km, acts like a shepherd, keeping ring particles inside a narrow range of orbital radii through a 42:43 outer Lindblad resonance. Galatea's gravitational influence creates 42 radial wiggles in the Adams ring with an amplitude of about 30 km, which have been used to infer Galatea's mass.