Orion

Orion was the name of a constellation. To observers on Earth, it was often likened to a human figure wearing a belt. (AUDIO: Autumn) According to Greek mythology, Orion was Artemis' lover and was placed in the sky after she accidentally killed him after being tricked by her brother, Apollo. (PROSE: Byzantium!)

Astronomical data
From southern England, it was possible to use Orion as a way to locate Traken. Nyssa told Andrew Harper that Traken was about halfway between Orion's belt and his left shoulder. (AUDIO: Autumn)

Stars in the constellation included Betelgeuse and Rigel, while the belt was formed by the stars Orionis Zeta, Orionis Epsilon, and Orionis Delta. The Horsehead Nebula, a cluster of stars, was also located near the centre of the constellation when viewed from Earth. (PROSE: Byzantium!)

History
The Osiran race placed great importance on the constellation. (PROSE: The Sands of Time)

While pointing out the constellation in the 1st century Earth sky, Ian Chesterton told Vicki Pallister about the mythological figure from the Greek mythology after which the constellation was named. (PROSE: Byzantium!)

In the 26th century, Orion was settled by androids fleeing from persecution in the Earth Empire. They set up an independent society that demanded any humans in their territory must accept android rule or get out. The Earth Empire could not abide the restriction, and waged the Orion War in retaliation. (AUDIO: Sword of Orion, Scorpius, et. al)

Parallel world
In a parallel world, the stars in the Orion constellation burnt out as a result of "the Darkness", (TV: Turn Left) also known as the reality bomb, which was detonated on the Crucible in the Doctor's world. (TV: Journey's End) This event was observed by Wilfred Mott through his telescope. (TV: Turn Left)