Super Mario Galaxy 2/Bowser's Galaxy Generator

Star 1: Bowser's Fortified Fortress
You start off on a planet with lumas on it. Avoid the fire wheel and use the launch star. In the second area, defeat the Hammer Bros. to reveal a flower type object. Jump up to grab onto this object and slowly float down to a cylindrical platform. Grab the spin drill to drill down into the third area. Avoid the Banzai Bills and drill into the soft earthy spots on the ground. Keep doing this until you reach the launch star. In the fourth area jump onto the moving platforms and make cloud platforms where neccessary. In area five, walk across the bridge and free Yoshi from the egg. Use Yoshi's tongue to grab onto the flowers. Continue on using Yoshi's tongue and land on a platform with two Boomerang Bros. Defeat them to unlock a trench for Yoshi to run through with the dash pepper. Use the launch star at the end of the trench to blast off to the sixth area. Keep up with the pink moving platform until you reach a platform with a large painting of Bowser. Leaving Yoshi behind, climb the lone pole up to where a yellow meteor is floating in midair. Like in previous levels, ground pound the meteors so that they fly into the circular stones.

Boss Battle: Bowser will work hard to defeat you by using his fist attack and fire breath. When the meteors land, they will release harmful purple shockwaves. Avoid the shockwaves and wait for bowser to punch near the fallen meteors. Jump on top of the meteor and smash it into Bowser. Do this four times to defeat Bowser. The fight is not over yet. Right when you are about to grab the grand star, Bowser returns and swallows it. In this fight good aim with meteors can save your life. As bowser comes closer to you, shoot meteors at him until he is gone for good.

Return Visit
You have defeated Bowser in the last world, but you are only partially done with the game. Come back to this mission with 120 power stars and defeat Bowser again. The level is no different from the first visit. After you defeat Bowser you will unlock the green stars.

Items
There are many red life mushrooms in this level. The first one is located in the first area on top of the pole to the way left. A second one can be found in area four on the low right side of the platform with the Dry Bones on it. A third can be found near the begging of the pink platform ride. A fourth and final one can be found in the area before the boss fight lying on the ground to the left. A 1-up mushroom can be found in area five. Near the lone Boomerang Bro. use Yoshi's tongue to grab the flowers to reach the 1-up mushroom. The Comet Medal is very easy to see. Near the end of the pink platform ride, quickly use Yoshi to flip on the flowers to reach the comet medal.

Star 2 (Prankster Comet): Bowser's Big Bad Speed Run
A slightly easier version of Star 1. You start with a time limit of 30 seconds, but you can pick up time extensions. You will not need to fight Bowser in the end.