Neptune

Symbol
Diameter	49532 km, 3.89 x Earth's
Mass	17.2 ME
Volume	54 VE
Average Density	1.76 g/cm3
Average 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°
Colour	Blue
Temperature	-180°C
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
Albedo	0.41

Neptune is the eighth planet in the Solar System, and the last of the gas giants. It was discovered in 1846 after observations of Uranus’ orbit showed that planet wasn’t moving in quite the way it should. Scientists suggested that another planet must be pulling on Uranus, and started the search for Neptune.

Neptune looks blue because, like on Uranus, the methane in the atmosphere absorbs all of the red light. The blue light from the Sun is reflected, but the red light is absorbed. This makes the planet 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 Pluto’s 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 Saturn’s because they are made of a much darker material that doesn’t reflect the Sun’s light so well.

Neptune has the fastest winds in the Solar System, reaching speeds of 2000 kph.

		Planets Introduction
		Mercury
		Venus
		Earth
		The Moon
		Mars
		Jupiter
		Saturn
		Uranus
		Pluto
		Asteroids
		Comets
		Meteorites
		Extra-Solar Planets

Authors: Carolyn Brinkworth and Claire Thomas

Last updated: July 2001