[Alneyan]

It seems rather random, though the side of the opened wormhole *may* be where the system is closest to the first system. Since my sentence makes no sense whatsoever... If you open a wormhole from a system X to the left of system Y, the wormhole seems likely to appear on the left side of system Y. Am I the only one with that feeling? Other than that, I think the location is random.

You can open wormholes to systems you haven't explored.