Grand Star

The Grand Stars are seven very large and powerful Stars in Super Mario Galaxy. As Mario gets these Grand Stars back, he gains access to different parts of Princess Rosalina's observatory. When one is found, a path to the next dome is created. Bowser has taken all of the Grand Stars and is using them for his own evil intentions.

At the game's beginning, Princess Rosalina provides Mario with a young Luma who is going to assist him in his quest to save the Power Stars. Mario then sets out through the Gateway Galaxy, eventually finding a Grand Star inside a metal planet. A Luma tells him that the Bad Guys are using the Grand Star to power Something. Mario must then complete a simple puzzle to free it. Mario receives the second Grand Star after defeating Megaleg. The third one is being used as a power source for Bowser's Star Reactor; Mario will have to defeat Bowser to get it. The fourth is being held captive by Bowser Jr.. The fifth is found in Bowser's Dark Matter Plant. The sixth is obtained by defeating King Kaliente in Bowser Jr.'s Lava Reactor. When 60 Stars have been found, Mario will able to fly to the Center of the Universe to confront Bowser for the final battle, where the seventh and final Grand Star is obtained. The grand stars have the same goal as the Keys from Super Mario 64.

Trivia

 * Strangely, only 5 out of the 7 Grand Stars need to be collected to reach the final battle.