Gateway Galaxy

The Gateway Galaxy is one of the many galaxies from Super Mario Galaxy for the Wii. Princess Rosalina calls this galaxy the "Gateway to the Starry Sky". It serves as the opening level for the game. This is the first Galaxy in the game, and after Mario clears the first level in the Galaxy, he won't be able to return until he unlocks the Garden, later on in the game. Although, you will only be able to visit the planet with the rabbits, that you started on.

Grand Star Rescue
When Mario awakens on this planet, a Space Bunny will challenge him to a game of hide-and-seek. The player will have to follow the bunny until he reaches his two friends, who will run and hide. One is found in a crater near the tree stump and a small lake, another in the grass near the Warp Pipe, and the last in a Warp Pipe. The player will have to catch them all, and a new structure on the planet will appear. Mario will meet with Princess Rosalina and gain the Star Spin ability. Mario needs to Star Spin the nearby Launch Star to reach the next planet, which has five Star Chips scattered about. To go to the next planet, Mario will have to grab the Star Chips to make a Launch Star and blast Mario to the next planet. Here, a Luma in a cage tells Mario that one of the Goombas on the planet has the key. The player will have to defeat the Goombas on the planet until one gives up a key. The Luma then transforms into a Sling Star, which slings Mario to the next planet. On this planet, Mario must defeat the Giant Goomba near the top of the planet to free the other Luma and enter the Warp Pipe. The inside of the planet is filled with yellow switches and moving electrical walls. A big machine stands in the middle of the room; a Grand Star is inside it. Mario needs to step on all the yellow switches to turn them blue, which will shut the machine down and reveal the Grand Star.

Gateway's Purple Coins
This Power Star is only accessible after the Garden has been opened. When Mario enters the galaxy, Rosalina will meet. A Red Luma notices how much Rosalina trusts Mario, so he gives Mario the challenge of collecting 100 Purple Coins scattered around the planet to earn his trust as well. There are seventy coins on the planet and thirty in the air. Mario must use the new Red Star power-up that gives him the ability of flight to reach the thirty in the air. Completion of this mission will award Mario with the game's sole Red Power Star. One collected, it allows for use of the Red Star power-up in the Comet Observatory.

Trivia

 * A planet in the Deep Dark Galaxy resembles the first planet of the Gateway Galaxy. It can be seen from a planet full of Electrogoombas. The planet is also reachable, but is much smaller. There are three Goombas, and a cork can be unscrewed using the star spin to shrink the planet and disappear, also revealing many coins.