Oort cloud

The Oort cloud, also known as the cometary cloud, was a region on the edge of the Solar system filled with asteroids in constant orbit around Sol. It was the point of origin of many of the solar system's comets. Counting this cloud, the solar system extended to a distance of about 1 and a half light-years or 40 billion miles from the Sun. (PROSE: To the Slaughter, AUDIO: Origins of the Cybermen)

An alien probe searching for signs of life used it as a base of operations. (AUDIO: Murmurs of Earth) By the 24th century, it had become a navigational hazard. To fix that and improve the system's feng shui, Robart Falsh and Aristotle Halcyon sold all the asteroids in the cloud to the Kilomons, Draconians and other alien races.. (PROSE: To the Slaughter)