Wikipedia:Today's featured article/May 19, 2010

The rings of Neptune were first detected in 1980, but only identified in 1989 by the Voyager 2 spacecraft. The rings are tenuous, faint and dusty, and resemble the rings of Jupiter more closely than those of Saturn or Uranus. Neptune possesses five known rings, each named for an astronomer who contributed important work on the planet: the Galle, Le Verrier, Lassell, Arago and Adams rings. Neptune also has a faint unnamed ring coincident with the orbit of Neptunian moon Galatea. The rings of Neptune are made of extremely dark material, likely organic compounds processed by radiation similar to that found in the rings of Uranus. The proportion of dust in the rings (between 20 and 70%) is high, while their optical depth is low, at less than 0.1. Uniquely, the Adams ring is divided into five discrete arcs, named Fraternité, Égalité 1 and 2, Liberté, and Courage. The arcs occupy a narrow range of orbital longitudes and are remarkably stable, having changed only slightly since their initial detection in 1980. How the arcs maintain stability is still under debate. However, their stability is probably related to the resonant interaction between the Adams ring and its inner shepherd moon, Galatea. (more...)

Recently featured: David A. Johnston – Marwari horse – Ratanakiri Province