I just pretend the map of planets is like the "Alderson points" used by Larry Niven and Jerry Pournelle from Mote in God's Eye.
Basically these points are distributed around a galaxy "randomly" (meaning there is mathetical relationships involved beyond my ability to explain). Not every star system has one, but each system theoretically has only one. So pretend that your game map is all of the known Alderson points. Some lead to useful places, some to dead systems. As for the star on your game map, just pretend it's a another useless system that doesn't even have gas giants, asteroid fields, space junk or anything...
From the book MiGE, there's a great quote where an amateur noted that the "Empire of Man" was a vast interstellar empire. In reality, man's control of the galaxy was limited to what amounted to a few hundred interspaced tiny bubbles in an ocean. And in between those bubbles, in the void not explored or linked by Alderson points, who knows what lay out there...
