The Enterprise-D approaches the McAllister C-5-Nebula.
The McAllister C-5 Nebula is a protostellar nebula located inside Cardassian space, approximately 7 lightyears from the Federation border and 11 lightyears from the Federation system Minos Korva.
The particle flux inside the McAllister Nebula prevents starships from staying in the nebula for more than 72 hours.
In 2369 the McAllister Nebula was used by Cardassian forces to hide their ships, in order to beginn a sneak attack on the nearby Federation system Minos Korva. However, this plan was blighted by Captain Edward Jellico, who commanded the USS Enterprise (NCC-1701-D) on a temporary assignment, and detected the Cardassian ships inside the nebula. (TNG "Chain of Command, Part II")