Neptune is a giant planet comprised largely of helium and hydrogen gases. It is the furthest of the eight planets from the sun, and it takes about 165 Earth years for Neptune to complete a full orbit. Neptune is also known for its six rings and 14 moons.
Neptune's mass is approximately 17 times that of Earth. Its small core is comprised of silicate and nickel-iron rocks, but most of the planet is a gaseous atmosphere. The rings that surround Neptune are thought to be made of ice particles coated with silicates or carbon.
Neptune's weather is thought to be characterized by huge storms, with winds gusting over 1,300 miles per hour. Two of these ongoing storms can be seen when looking at Neptune through a telescope: the Great Dark Spot and the Small Dark Spot. Much of what is known about Neptune has been gleaned from observations made by Voyager 2, a spacecraft that passed by the planet in 1989.
Of Neptune's 14 moons, the largest is Triton, a spherical moon that is thought to be the coldest body in the solar system, with an estimated temperature of minus 235 degrees Fahrenheit. Four of Neptune's moons, Naiad, Thalassa, Despina and Galatea, are so close to the planet that they are actually found within its rings.