Sense Sphere

The Sense Sphere was the homeworld of the Sensorites.

Geography
The Tenth Doctor confirmed that the Sense Sphere was located in the same star system as the Ood Sphere. (TV: Planet of the Ood) It had two suns, which meant the planet never had natural night-time. Its atmosphere was thick, which meant sound waves on the planet were increased in volume. The planet was also riddled with caves, which is where the Zilgans lived. (PROSE: The Monsters from Earth) It was also rich in molybdenum. (TV: The Sensorites)

History
Early in its history, the First Doctor, Tony Barker and Amy Barker visited the Sense Sphere, where they angered the native Sensorites when the Doctor killed a Zilgan. However, they scared them off by shouting and escaped. (PROSE: The Monsters from Earth)

In the 28th century, the Sense Sphere was visited by two separate Earth expeditions desperate to harvest the planet of its precious molybdenum. The first expedition left for reinforcements in mining the planet but crash-landed, bringing a disease to the Sensorites which wiped out thousands of their number for years to come. The second expedition was kept prisoner by the Sensorites to ensure their planet's future. The First Doctor ensured that the Sense Sphere would not end up exploited by humans, as the native Sensorites would rather they left them alone. (TV: The Sensorites)

The Sense Sphere finally capitulated to the Earth Empire in the 30th century. (PROSE: Original Sin)