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Neptune (or Sol VIII) was the eighth planet in the Sol system.

It was discovered in 1846 by Johann Galle. (PROSE: Neptune)

It was situated 4.5 billion kilometres from the Sun and 4.3 kilometres from Earth. Wind reached speeds of 2100 kilometre an hour, and surface temperature was -218 degrees centigrade. (COMIC: Terrorformer)

On 14 May 2007, Mary Barton teleported herself to Neptune after an argument with her father. She was returned home by the Seventh Doctor, narrowly averting an interplanetary war. (PROSE: There's Something About Mary)

A Hyperion ship that fled the Great Inferno, took refuge on Neptune and started reawakening in 2114. (COMIC: Terrorformer)

Methane-breathing octopuses lived in the atmosphere of Neptune in the 32nd century. (PROSE: The Eye of the Tyger)

Iris Wildthyme claimed to have saved the Doctor's life on Neptune during an encounter with the Ice Warriors. (PROSE: Verdigris)

By the 38th century, one of its moons, Triton, was inhabited by humans. The Le Verrier space station orbited Neptune during their golden period of prosperity, but the station eventually fell from orbit due to the malicious use of Morpheus sleep deprivation pods that accidentally created the Sandmen, which evolved into sentient carnivores and attempted to spread to the rest of the Solar System. The Twelfth Doctor tried destroy the Sandmen by instigating the Le Verrier's freefall into Neptune's atmosphere, but one Sandman survived and rode the crashing station down toward Neptune, plotting to release the infectious specimens of the Sandmen species on the unsuspecting world below and anyone else who learned of his fate. (TV: Sleep No More)