How to find all alien species?

Had a good run so I made a long trek out there and visited all 182 systems, but met just 6 alien species. the achievements suggests there are up to 15. Where can I find the rest? Random encounters while travelling?

There was some discussion about this in the past, but I can't find the thread anymore. Bear with me here, because it was a while ago and I don't remember everything clearly.

(Spoiler Alerts, btw, for readers who care.)

6 alien races sounds about right, in terms of the ones you can actually talk to. Maybe 9 if you count Judges/Architects, People Death and Star Iron (which I'm not sure the game does count.) I don't think species observed in random encounters count for the purpose of the achievement.

I'm pretty sure the past discussion established that it's not possible to meet enough aliens right now to make that one achievement, but I believe the upcoming Omega Edition will be adding more to correct that issue.