System J-25 was a planetary system that had at least six planets. The nearest Federation starbase to this system, in 2365, was Starbase 185.
The sixth planet was class M and previously inhabited by an intelligent species.
In the 24th century, the Borg had a presence in the system. A Borg cube scout detected the Federation starship USS Enterprise-D when it was transported to this system by Q in 2365. Shortly after, the Enterprise-D made first contact.
Guinan was familiar with the area of space in which System J-25 was located. (TNG: "Q Who")
According to Star Trek: Star Charts (p. 13) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), System J-25 (FGC-J25) was located in the Beta Quadrant. The system's primary was an A-class star. This system was located near the Borg transwarp network.
