Defenses will always be hostile toward the players. Since a player does not know what is in any hex until he enters it, he is likely to encounter a star in the course of any long move. However, a ship does not have to stop for a star, even if the star is owned by another player. If you pass through a star hex owned by another player, but do not stop, you will learn that there is a star there, and that the system is owned by another player. You will not know what its BP value is or who owns it.
Movement is sequential.
The referee determines the movement sequence randomly each turn. He moves all the ships belonging to one player before he moves any ships belonging to the next player. A player is said to own a star hex if he can keep a ship on that hex for one full turn without having any enemy ships present. If the star was previously owned by another player, he must destroy or drive off all defending ships and then keep a ship there for one full turn without combat. When a player takes possession of a star, he controls its BPs.