Neptune is the farthest planet observed by binoculars. By the 19th Century, Neptune was discovered. Its discovery was the prediction of French scientist, Le Verrier, based on the calculation of Uranus orbit. Le Verrier predicted there might be another planet beside Uranus and informed Berlin Observatory to look for the trace. In the end, this planet was discovered and its position only has less than 1 degree difference as the predicted position as Le Verrier proposed. The discovery of Neptune once again proves the Principle of Gravitation.

Neptune has the Atmosphere composed by hydrogen, nitrogen, methane and other hydride. Because methane absorbs red light, Neptune appears to be blue color.

Like "Great Red Spot" on Jupiter and "Great White Spot" of Saturn, Neptune has "Great Dark Spot." There are white clouds floating above "Great Dark Spot" and they may be the frozen methane. "Great Dark Spot" revolve in anti-clock direction and the cycle lasts for 16 days and it also revolve a circle on Neptune every 18 hours.