|Diameter||49532 km, 3.89 x Earth's|
|Mean Density||1.76 g/cm3|
|Mean Distance from Sun||4497 x 106km = 30.058 AU|
|Eccentricity of Orbit||0.009|
|Inclination of Equator to Orbit||28°|
|Inclination of Orbit to Ecliptic||2°|
|Atmosphere||Hydrogen, helium and methane|
|Length of Day||16.1 hours|
|Length of Year||165 years|
|No. of Moons||8|
|Gravity||1.194 x Earth's|
|Escape Velocity||24.6 km/s|
Neptune is the eighth planet in the Solar System, and the last of the gas giants. It was discovered in 1846 after observations of Uranusí orbit showed that wasnít moving in quite the way it should. Scientists concluded that another planet must be pulling on Uranus, and so started the search for Neptune.
Neptune looks blue because, like on Uranus, the methane in the atmosphere absorbs all of the red light. Therefore the blue light from the Sun is reflected, but the red light is absorbed, causing the planet to appear blue. The planet also has a dark spot, which is a huge storm in the atmosphere, similar to Jupiter's Great Red Spot.
Neptune was actually the furthest planet from the Sun between 1979 and February 1999 because Plutoís orbit is so elliptical that it sometimes passes within Neptune's.
Neptune has rings like those of Saturn made of dust and small pieces of rock. They are much harder to see than Saturnís because they are made of a much darker material that doesnít reflect the Sunís light so well.
Neptune has the fastest winds in the Solar System, reaching speeds of 2000 kph.
Authors: Carolyn Brinkworth and Claire Thomas
Last updated: July 2001