Bowser Jr.'s Lava Reactor

Bowser Jr.'s Lava Reactor is a galaxy in Super Mario Galaxy. This is where Mario battles King Kaliente once again and receives a Grand Star. The galaxy is one extremely large planet made completely out of lava with very few rocks.

King Kaliente's Spicy Return
Mario lands on a small planet with a few Goombas, a Bullet Bill cannon, a caged Launch Star and a black hole at its center. Lure the black hole to the cage to smash it and free the Launch Star. Use it to zoom to the surface of the Lava Reactor, which is entirely lava, sans a few platforms. Mario will encounter two enemies that fire fireballs and rocks at him, which Mario will have to defeat to get another Launch Star. From there, Mario will go on to fight a very strong version of King Kaliente. Upon defeating him for the second time, he will recieve the fifth Grand Star.