Got him.
I'm newly returned to the game and rusty in lots of ways. One of the things I've been sloppy about is no passive sensors. I just run around with actives on and, consequently, anyone can see me coming long before I see them.
So I put some 100-ton thermal and EM passives on my fleet leaders and started running a bit quieter. Then I sent 1st fleet in to shadow a geo survey ship. Spotted badguy lurking at Ross A-II, unmoving and occasionally strobing his actives. I was able to approach to around 30m before he spotted me and started running, at which point I launched 20 Mk4 Sparrows at him--9 warhead, ~36000kps, range of about 100m. He fled at his top speed of 12,500 but that's still well within my reach.
So, whats going on:
The Solari Empire has settled about half a dozen systems, and has explored about a hundred. The game was created, I think, with one NPR, and at around 2065 I hit the button that created another. It's 2073, and still no sign of either. All known infestations of the race known to us only as the "Assholes," with whom our diplomats are utterly unable to communicate, have been cleared, though we expect to find more as we search ever further. Those guys are everywhere.
We're stepping up the survey program, in hopes of finding some lifeform somewhere that we can communicate with, and then conquer.