Named for the Roman god of the sea, the solar system's eighth planet was discovered in 1846 by France's Urbain J.J. Leverrier and England's John Couch Adams, although they were working independently. The astronomers had observed that something was disturbing the orbit of Uranus, and mathematical calculations as to its location soon unveiled Neptune. Intriguingly, the planet was almost identified as early as 1612 by Galileo, but he mistakenly classified it as just another star.
Neptune has 13 known moons, but Triton is perhaps the most unique due to its unusual backward orbit. This odd orbital pattern, the only one known to occur in our entire solar system, has caused some astronomers to speculate that the moon was actually captured by the planet sometime in the distant past from Triton's original location in the Kuiper Belt, a collection of icy objects clustered in a disk shape on the extreme edge of our planetary system.
Neptune's rings are also unique in that unlike those around other planets, the ones circling Neptune seem to defy the laws of motion. The planet has three arcs named Liberty, Equality and Fraternity. What has puzzled scientists for years, though, is why the arcs haven't spread out to form a uniform ring. Astronomers now theorize that the gravitational forces from Galatea, one of Neptune's moons that lies closest to the rings, keep them narrow.
If the data received from probes of Neptune is correct, there is no solid surface on the planet. Instead, the rocky and icy core is completely surrounded by a liquid layer that in turn is smothered by dense gases. The atmosphere around the planet contains thick clouds that are blown around the sky by winds up to 700 miles per hour. Areas of swirling gases create features resembling giant hurricanes that can last for years. One of these supposed storms, the Great Dark Spot, was discovered by Voyager 2 in 1989, seemed to dissipate in 1994 and then appeared to be reforming a year later.