Rigel XII, also known as the Rigel mining planet, was the sparsely inhabited twelfth planet of the Rigel system. Rigel XII was located in the Alpha Quadrant, and Earth was less than ninety light years away. An asteroid belt was located less then two days away at impulse speed. (TOS: "Mudd's Women", "I, Mudd"; ENT: "Two Days and Two Nights")
Conditions on the planet were harsh, and Human habitation was only possible in sealed pressure domes. The atmosphere was capable of supporting humanoid lifeforms. Grit and dust were everywhere, and sandstorms were a frequent occurrence. These storms were especially bad during a magnetic storm. Water was scarce, and plant life was twisted and sere.
In the mid-23rd century, Rigel XII was the site of a lithium mining operation run by Ben Childress with two partners. In 2266, con artist Harcourt Mudd, using the illegal Venus drug, attempted to sell Eve McHuron, Ruth Bonaventure and Magda Kovacs to the miners. (TOS: "Mudd's Women")