The Trial Galaxies are 3 galaxies in Super Mario Galaxy on the Wii that are meant to be more challenging then the other galaxies. To access them, the player must collect all 3 Green Stars in the game. Then back at the Comet Observatory, a green Launch Star will appear. This will lead the player to an oddly shaped planet. On that planet, the player can talk to 3 green Lumas and each one of them will send Mario to a trial galaxy. The planet where Mario can access the trial galaxies is also the planet where Mario can access the Grand Finale Galaxy.
Rolling Gizmo Galaxy
Gizmos, Gears, and Gadgets: The player must complete the ball rolling challenge on a harder path.
The Galaxy's Greatest Wave: The player must ray surf across a dangerous surf.
Bubble Blast Galaxy
The Electric Labyrinth: The player must go inside a bubble and blow it around an electric maze.