Hi
I used to love Stars! years ago, and still have it via Dosbox.
However, IMHO, Stars is quite a different game.
Aurora4x is primarily a single player 4x game, with emphasis on the whole exploring, logistics in addition to the combat.
Stars! is actually more of a multiplayer PBEM military turnbased strategy wargame. All aspects of the game (exploring, terraforming, colonising) has to do with making your war economy stronger in the most efficient time, to eventually kill off all the other players and be the last one standing. There is a single player option, but the AI is pretty limited. Pity there's hardly any Stars! players anymore. The game is simple to play, but has enormous depth & complexity.
Nonetheless, Stars! was a fantastic game, and 20+ years on, there still isn't anything close to the briliance that Stars! had. VGA planets tried to copy it, but its just not as good.
The only game i've come across that has that similar PBEM wargame with high depth is the Dominions series, albeit with a fantasy setting.