A solar system is a single star and all the planets, asteroids and other astronomical features that orbit it or are within a reasonable distance. However, since the gap between each star is so huge, features are simply grouped with the closest star, so there is no set distance.
In Spore, you cannot traverse your own solar system until you have built a UFO. Will Wright has suggested that most solar systems have between four and five planets or other celestial bodies, although more may be possible. It is uncertain whether there will be any solar systems with multiple stars, although there is confirmation that there will be different types of stars (such as red giants).
Galvopa system is a solar system. Known planets are Lamstus, Bilzac and Cattor.
Galna system is a solar system. Known planets are Galarid and Galta.