Super Mario Galaxy/Green Stars and Trial Galaxies

To get to the three Trial Galaxies, you first have to find the green Power Stars. After you find the green stars, you play the Trial Galaxies by using the Green Launch Star in the Comet Observatory near the three green Lumas, which are the three green Power Stars of course.

Green Stars
Go to the Hungry Luma under the platform in the Dusty Dune Galaxy. Feed it some star bits to turn it into a new planet. Take the Pink Launch Star to the planet that looks like a pyramid. Find the five silver stars by controlling where the sand moves. Don't get crushed! Once you find all five stars, the sand disappears and at the very bottom is your first green Power Star.
 * Star 1

Go to Buoy Base Galaxy and swim underwater. Lure the Torpedo Ted into a glass cage that has a pipe in it. Once you go in the pipe, avoid the Bullet Bills and lure one into the glass cage that has the second green Power Star.
 * Star 2

You can get this star when you've received a message from Luigi. Go to Battlerock Galaxy. Go to the saucer with a glass cage with Luigi trapped in it. Lure the Bullet Bills into the cage that Luigi is inside. Once you set him free, he will give you the third and final green Power Star. Jump on Luigi's head to bounce into the star.
 * Star 3

These stars can be attained in any random order.

Star 1: Gizmos, Gears, and Gadgets
Get on top of the rolling ball and controll it to get across the zigzag path, then jump into the blocks to break them and receive coins. Jump into the bridge to make it fall down. Then stay in the hole (break the blocks first) until it lauched you, then keep going. Watch out for the bombs, and at the end jump on the moving dice to get up the ledges.

Star 1: The Galaxy's Greatest Wave
You start on one of three floating islands. The first one you see will have little penguins who remind you how to Ray surf. The one to the right of you will have another small penguin and a rock circle you can collect star bits from. The last island has a podium and the coach penguin

The coach penguin will tell you that you have 3:00.00 minutes to complete the course. You will need to navigate this difficult course carefully. There will be plenty of twists, jumps, and turns. The best way to navigate these is to tap the a button instead of holding it down. The faster you tap the faster Mario will go. The best way to take on jumps is to let go of a before you fly too far. You’ll need to stop and get your bearings before you keep going.

You will have plenty of time to finish before 3:00.00, but you will probably fall off a lot. Once you finish before 3:00.00 you are given a star by the coach penguin and he will tell you that he knows you can do better than that. If you finish before 1:30.00 then he will change his dialogue and he will say he’s amazed that you did it that fast.