Solar System: Neptune

Neptune is the eighth and farthest known planet from the Sun in the Solar System. It is the fourth largest planet by diameter, and the third largest by mass; Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 14 Earth masses, but Neptune is slightly smaller in volume due to its higher density. The planet is named after the Roman god of the sea. Its astronomical symbol is Astronomical symbol for Neptune. The symbol is a stylised version of Poseidon's Trident, as well as the alchemical symbol for Quicklime (Calcium oxide).