Neptune Planet

 The planet Neptune gets its name from the ancient Roman god of the sea. Along with Jupiter, Saturn, and Uranus, it is one of the immense, gaseous outer planets called Jovian, meaning “Jupiter-like.” Unlike the inner, Earth-like planets, these gas giants have no solid surfaces.  Neptune is normally the eighth planet from the sun.  However, about every 248 years, Pluto's highly eccentric orbit crosses paths with Neptune's.  At that time, Neptune becomes the ninth and farthest planet in the solar system for a period of 20 years, as it was in 1979–99. Neptune travels around the sun in a nearly circular orbit at an average distance of about 4.5 billion kilometers. 

 Like the other gaseous planets, Neptune spins quickly on its axis, once every 16.1 hours, and has a somewhat larger diameter at the equator than at the poles. Its equatorial diameter of about

Although the planet is less than 30 percent as dense as the Earth, it is the densest of the gas giants. This higher density suggests that Neptune's interior contains a greater percentage of molten rocky material and melted ices of methane, ammonia, and water than do the other Jovian planets. However, astronomers doubt that Neptune has distinct layers, as do Jupiter and Saturn. Surrounding the heavier interior is a massive atmosphere of about 83 percent hydrogen and 15 percent helium, a composition similar to that of the sun and the other gas giants. Methane, which accounts for about 2 percent of the atmospheric gases, gives Neptune its bluish color. Hydrogen and helium are almost invisible, but methane absorbs most of the red wavelengths of light. The light reflected off the planet's clouds thus lacks red and appears bluer. Some researchers speculate that the heat and high pressures of Neptune's atmosphere may crush the methane, causing it to decompose into carbon compounds and diamonds that fall like hail toward the planet's