Neptune is a blue planet like our own earth. Its inner two third is rocky and the outer one third is gaseous. The gases on Neptune are mainly hydrogen, helium and methane. From the outside it is, therefore, like Jupiter which is a gigantic gaseous ball. It is much smaller than Jupiter though and much further too.

It is, therefore, not visible to the naked eye and a telescope is required for the purpose. The mass of Neptune is only seven times that of Earth while its volume is 58 times that of Earth indicating its gaseous content. That is enough volume to accommodate sixty earths.

Neptune is so far from the sun that it receives very little sunlight. Naturally, it is a cold planet. But this gaseous mass is far from tranquil. The clouds in Neptune are highly turbulent. It is the windiest of all the planets and enjoys the reputation of having the most severe storms. While the storms on our planet earth are known to reach maximum speed of 300 to 400 kilometers per hour, in Neptune, storms with wind speed up to 2200 kilometers per hour have been recorded.

Much of the information we have about Neptune has come from Voyager2. This space probe made observation of an enormous dark spot, similar to the Great Red Spot of Jupiter. The size of the spot is so large that earth will fit into it. This spot is a gigantic anticyclone which circles the planet in 18 hours. Another smaller spot was also observed sweeping around Neptune in slightly lesser time.

An interesting fact about Neptune is that it was not discovered through observation as in the case of other planets. It was discovered after its existence was predicted through mathematical calculations. As early as 1613, Galileo observed Neptune through his telescope but concluded it was a star.

In 1845 Le Verrier started examining the irregularities in the orbit of Uranus and concluded that this must be due to the gravitational force of a nearby planet. Based on this hypothesis, Johann Galle of Berlin Observatory started looking for this nearly invisible planet and eventually found it in 1846 very close to its predicted position. It was a classic case of theoretical prediction in science borne out through experimental observation.

Neptune has thirteen satellites of which the largest one is called Triton. It is a sphere covered in ice which is falling towards Neptune. Five of these satellites were discovered only recently. Neptune also has rings which were observed in detail by Voyager. From the Earth the rings look very faint. These rings are not homogeneous and contain clumps of matter.

Neptune rotates around its axis in about 16 hours. Being very far from the Sun, it takes 165 Earth years to revolve around it. It has a highly tilted magnetic field. The tilt is thought to be account of flows inside the middle layers of Neptune, possibly water. If that is true, it will justify its name which is taken from the Roman God of the Sea.