Neptune (Planet) - November 24, 2012

Eighth planet in distance from the Sun, fourth largest planet in diameter, and third largest in mass in the solar system. Neptune’s gravity has a major influence on the Kuiper Belt, a region of icy bodies in the outer solar system that is a source of comets and includes the dwarf planet Pluto, formerly counted as the ninth planet.

Because of its great size and mass, scientists classify Neptune as one of the giant or Jovian (Jupiter-like) planets—along with Jupiter, Saturn, and Uranus. Like Uranus, Neptune is also classified as an ice giant planet, mainly made of the ice-forming molecules water, ammonia, and methane as a liquid mixture above what is thought to be a rocky core. Its atmosphere is mainly hydrogen and helium, along with methane gas that gives the planet a blue-green color.

Neptune orbits the Sun at an average distance of about 4,490 million km (about 2,790 million mi) in a period of 165 Earth years and only receives about 1/900th the amount of sunlight that Earth does. Neptune’s diameter at the equator is about 49,520 km (about

 30,767 mi). Even though Neptune’s volume is 72 times Earth’s volume, its mass is only 17.15 times Earth’s mass.

Neptune has four rings and 13 known moons. The planet is named after the sea god Neptune in Roman mythology.

Neptune - the eighth planet.