Portal

"Through space and time to an unknown world we go! I'm jiggling just thinking about it! Ready, Captain?"

- Lubba

A portal is a powerful cosmic gateway found solely in Super Mario Galaxy 2. Portals are greenish-white in color and round in shape, and they allow Starship Mario to transcend the boundaries between all seven worlds found in the game. A portal is created via the power of a Grand Star. When Mario returns to Starship Mario after having defeated Bowser, Bowser Jr., or one of Bowser Jr.'s henchmen or machines in one of the six boss galaxies in the game, the Grand Star that he returns with will immediately shoot out into space directly in front of Starship Mario and explode into a portal. Access to the next sequential world in the game will then be granted.

Originally, the first time a new portal appears in the game, a short cutscene will play, in which Lubba talks to Mario before he pilots Starship Mario directly into the portal, thereby advancing to the next world. After each cutscene, the portals that are created will remain at the beginning and end of each world (with the exception of World 1 and World S, which have portals only at the end and the beginning, respectively), allowing the player to freely travel between all unlocked worlds whenever they want. Alternatively, the player could also use the Grand World Map, which, though the portals are not physically shown when the map is in use, also requires the physical presence of a portal to allow Starship Mario to travel between worlds quickly.

Trivia

 * If the players go to Starship Mario while they are in a space before the portal to the next world, they can see the portal floating in the sky. The same applies when Starship Mario is in a space after the portal to the last world, but this time the portal can be seen behind Starship Mario.