The Grand Star is a very big and powerful star that will help Mario
during their adventure in Super Mario Galaxy
. There are 7 in all for them to collect during the game and it can be earned by defeating bosses like King Kaliente and Bowser
. It is also the Comet Observatory
's power source. In order to reach Bowser's Galaxy Reactor
, you need at least 5 out of 7 to gain access. The Grand Stars return in Super Mario Galaxy 2
, where you can earn them at the end of each world by defeating Bowser Jr.'s inventions, and Bowser himself. Altogether, there are 13 Grand Stars in both games.