Tarkin's Gambit: The Vader Contingency
Penumbra is the name given to the planet Grand Moff Wilhuff Tarkin has selected for his hand picked group of scouts to set up a passive sensor post to observe hyperspace traffic in the area. It is surrounded by a large asteroid field making it difficult to find and harder to get to. It also has an unusually high concentration of Iodine in the water, giving the water an orange tinge but the atmosphere and flora purple hues.
The native sentient species on the world are the Kumumgah.