Is there any difference between matter and antimatter other than the charge? Could we (theoretically of course) find in space a civilization made of antimatter?
The operator $C$ replaces every particle with its antiparticle. If $C$ is a symmetry of the universe, then there is no difference between matter and antimatter. However $C$ is not a symmetry. This can be seen in that all neutrinos are left-handed, but antineutrinos are right-handed. There is also evidence that kaons and antikaons have different rates of decay. This suggests that $CP$, which includes also a mirror transformation, is a candidate symmetry. Experiments show that $CP$ is not an exact symmetry, but the violation is very small. So an antimatter star or galaxy is not ruled out.
If you can convincingly explain why we don't see any antimatter galaxies, you would have good reason to plan a trip to Stockholm.