The Ferrous Aurora Nebula, a region filled with thick, reddish gas, existed within the Thesme sector. Because of the Ni'lyahin Smugglers operating there, traversing the nebula was hazardous throughout the time of the Galactic Civil War.
The Star Wars: The Essential Atlas Online Companion situated the nebula in the Thesme sector, even though it was initially associated with the Yavin system.