Neptune is the eight planet and was discovered by astronomers John Couch Adams and Urbain Jean LeVerrier. It is slightly smaller than Uranus, and spin once every 19.2 hours. Neptune is about 2,799 million miles from the Sun. It takes about 165 Earth years to complete a single orbit. Neptune can be seen with the naked eyes and better yet, through a telescope. It appears in the form of a blueish circle. This image was taken by Voyager 2 in 1989.
Neptune’s Atmosphere is made up of Methane gas on its surface which helps to give it its blueish appearance. It also contains ammonia and helium. Beneath its dense blanket of gases, the planet is thought to have an outer layer of liquid hydrogen.
Voyager 2 observed long, swirling clouds swirling around Neptune blown by winds of up to 1,243 miles per hour. It also saw dark spots with the largest named the Great Dark Spot which looks like the size of the earth. Voyager 2 scientists named the little cloud below it the Scooter because it raced around the planet every 16 hours.
Neptune has eight moons with the largest of them named Triton and Nereid. Triton is bigger than the planet Pluto. Most moons orbit their planets the same direction as the planet spins. Triton, however travels in the opposite direction as shown below. Triton’s surface is bright and smooth. It has some dark streaks over it and pink ice around its south pole. Triton has a thin atmosphere of Nitrogen and Methane as similar to Saturn.
Despite its great distance from the sun and lower energy input, Neptune's winds are three times stronger than Jupiter's and nine times stronger than Earth's.
In 1989, Voyager 2 tracked a large, oval, dark storm in Neptune's southern hemisphere. This hurricane-like Great Dark Spot was observed to be large enough to contain the entire Earth. It spun counterclockwise and moved westward at almost 750 miles (1,200 kilometers) per hour. (Subsequent images from the Hubble Space Telescope showed no sign of the Great Dark Spot photographed by Voyager. A comparable spot appeared in 1994 in Neptune's northern hemisphere but had disappeared by 1997.) Voyager 2 also photographed clouds casting shadows on a lower cloud deck, enabling scientists to visually measure the altitude differences between the upper and lower cloud decks.
The planet has six rings of varying thicknesses, confirmed by Voyager 2's observations in 1989. Neptune's rings are believed to be relatively young and relatively short-lived.