The location of Luyten 789-6 on a star chart
Luyten 789-6 was a star that was located approximately eleven light years from Sol.
In 2364, the location of Luyten 789-6 was labeled in a star chart of a stellar neighborhood with Sol at the center. This chart was stored in the USS Enterprise-D library computer. Later that year, the chart was scanned by Outpost 63. (TNG: "The Naked Now", production art; TNG: "The Last Outpost")
This star chart naming stars within twenty light years of Sol was drawn by Rick Sternbach for the Star Trek Spaceflight Chronology in the late 1970s. Found on page 77, this chart showed Earth commercial and exploration routes after the use of warp drive began. There were no commercial or exploration routes to this star. This is probably because it is in fact a three-star system, and two of the stars are closer to one another than Mercury to Sol, with none further from another than the distance between Mars and Sol. A stable, habitable planetary body in such a system would be very unlikely.