The Horsehead Nebula was a nebula located within the galaxy of Mutter's Spiral. It was located in the constellation of Orion about 1500 light-years from Earth.
The planet Dramos was located in the Horsehead Nebula, (PROSE: The Mary-Sue Extrusion) as were the Ood Sphere (TV: Planet of the Ood) and the Sense Sphere.
During the Millennium War, the Mad Mind of Bophemeral attempted to create a wormhole in the Horsehead Nebula which would have killed quintillions had his plan not been stopped by the Osirans. (PROSE: The Quantum Archangel)
The Uvodni fought the Ghost Wars against the Malakh Empire within the nebula. (TV: Warriors of Kudlak)
In 2006, a plasma storm was occurring in the Horsehead Nebula. The Ninth Doctor planned to ride it with the TARDIS and invited Rose Tyler to come along. (TV: World War Three)
The Tenth Doctor took Grayla to either the Horsehead Nebula or the Crab Nebula. (COMIC: The Whispering Gallery)
In the 1890s, the Sixth Doctor told Henry Gordon Jago and Professor George Litefoot that he had an appointment in the Horsehead Nebula in the 29th century. (AUDIO: The Hourglass Killers)
According to the Third Doctor, the Nurazh came from the Horsehead Nebula. (PROSE: The Touch of the Nurazh)
The Eleventh Doctor and Amy Pond discovered Mr Jones SOS around the Horsehead Nebula. The Jones family was attacked by a Dalek scientist. (GAME: The Mazes of Time)
Other references Edit
Ian Chesterton showed the Horsehead Nebula to Vicki Pallister in the Earth sky. He described it as globular cluster of stars resembling "a boy scout's badge". (PROSE: Byzantium!)