The Size of a Galaxy

The maximum is over 500 planets. However, in reality, anything more than 90 (some would say 70) planets will eventually lag the game to the point where it is nearly unplayable.

Also depends what the total fleet capacity is, as well.  Playing at a scaled fleet capacity of 1000 works wonders on lag.

It also depends on a few more factors.

Some maps with over 100 planets run better than some with only 80 planets.

The ammount of stars doesnt seem to be the cause for this performance difference, so the question of why remains unanswered, at least to me.

Numbers of planets aren't much of an issue, its mainly the fact that when every planet has its tactical/logistics slots filled and there are trade ships all over the place with multiple race that it gets super bogged down.

Adding more and more planets (when in a late game scenario) just amplifies the problems.  So really, you can make it as large as you want but will it take forever to finish a game? YES, will it eventually become super laggy at the end of a game? YES.

I could be wrong but I believe that the only 'real' limit outside of lag issues (as are described above) is 1000 phase lanes and then the game starts eating them ...

yarlen had told me that there is  hard limit of 512 planet names & 512 star names in the engine.

harpo

Can there be duplicate names on a map though?

I think so, there is no where close to 500 names defined in the string file, yet I've played (just briefly) maps of close to that size. Also if it's a custom map you can give them custom names.

All Star and planets name of Sins:

https://www.sinsofasolarempire.wikia.com/wiki/Star_And_Planet_Names