Neptune

The presence of Neptune was suspected before it was discovered based on deviations in Uranus' orbit that didn't follow Newton's laws. J.C. Adams and U.J. Leverrier independently used Newtonian celestial mechanics to predict the mass and orbit of this suspected planet. It was then found in 1846 by Johann G. Galle and Heinrich Louise d'Arrest at the Berlin Observatory very near the predicted position. Normally, Neptune is the second farthest planet from the sun. However, Pluto has such an eccentric orbit that for part of its orbit Neptune is the farthest planet from the sun. From January 1979 through February 11, 1999, Neptune was the farthest planet from the sun.

Neptune is very similar to Uranus. It too appears blue in color due to the absorption of red light and the reflection of green light. their internal compositions are probably similar as they have similar bulk densities and masses. The atmosphere of Neptune has faint cloud bands that are probably made of water ice and ammonia ice with gaseous methane, hydrogen and helium. Two differences are that ethane has been found in Neptune's atmosphere but not in Uranus' and Neptune has internal heat. Voyager 2 discovered markings in Neptune's upper atmosphere such as the Great Dark spot, which is seen in the above picture of Neptune. However, this dark spot has since disappeared. Neptune, like the other gaseous planets has high speed winds. However, Neptune's winds are the fastest among the planets. These things are evidence indicating that Neptune's atmosphere changes rapidly.

moons: 8; Triton is the largest, the seven smaller moons are Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, and Nereid