Super Mario Galaxy/Space Junk Galaxy

Space Junk Galaxy is accessible from the Fountain observation dome. You need 9 Stars to enter.

Star 1: Pull Star Path
In this mission, there are pull stars everywhere. Use them by pointing at them and pressing. Shake the Wii Remote or press to release yourself. Follow a path to a set of three glass planets. Collect the five yellow star chips for a launch star, but watch out for the Amps circling the planets. Now you are on a rocket. Use the pull stars inside the planets, then follow an even longer path of pull stars. At the T-shaped planet, avoid or defeat the spiders and save all the Toads by breaking the crystals. The captain appears on the Starshroom and tells you to use the Sling Star. Do so to land on a platform. More platforms will appear when you walk forward, and the path will be revealed. Find the five Silver Stars, but try not to fall, as there is a black hole below you. The Power Star appears where you started.

Star 2: Kamella's Airship Attack
You start on the green Starshroom. Take the Launch Star to an airship. Break the crates if you want, then spin the lever to lower the bridge. The bunnies tell you to jump and spin to reach higher places. Jump and spin to break the crate on the high pillar, then take the sling star to another airship. Free the Toad if you want, who tells you to use shells to break open treasure chests. Take the shell and throw it at the chest behind the Magikoopa to reveal a Launch Star. Take it to a tilting platform with a Goomba. Fall off the platform onto a third ship, then use shells to defeat the octopuses. A red shell is in a chest for better aim. Defeating the octopuses lowers the bridge, which you can use to get to a Sling Star that takes you to the boss fight.

Boss Fight: Kamella
At the start of the fight Kamella uses Fireball and Shell, so chuck a shell at her for the first hit. Note she is behind the ship and the shell can hit the railings so jumping and throwing the shell makes it easier. Next she hovers over the ship and the fireball splits into two, so repeat the strategy. Now Kamella realizes she needs back-up and uses Summon Magikoopas, so take them out then hit Kamella for the star.
 * Attacks
 * Fireball: Kamella throws red energy at Mario which eventually turns into a fireball. After you inflict more hits then the red energy splits up into more fireballs.
 * Shell: Kamella throws green energy at Mario which eventually turns into a shell. The shell doesn't actually hurt you but the green energy does. You need to spin near it to catch it when it is moving.
 * Summon Magikoopas: Kamella summons two Magikoopas to help her. The easiest way to defeat them is to throw shells at them, but you can also spin or stomp them.
 * Strategy

Star 3: Tarantox's Tangled Web
For the time being, ignore the Hungry Luma you meet on this level.

Boss fight. Jump into a 'sling pod' (a sticky part of the web), pull yourself back using the pointer, and launch yourself at the Tarantox's backside. Tarantox will turn upside down, and you should then launch yourself at the three weak points on its underbelly. Repeat. If you are having trouble getting behind Tarantox, run along with the acid until Tarantox stops. Using a sling pod, shoot yourself into one of the pods on Tarantox's side. This will stun Tarantox, allowing you to get behind it.

Star 4 (Speedy Comet): Pull Star Path Speed Run
Available when a Prankster Comet is in this Galaxy. Do the same as for Star 1, only within a 4 minute time limit. There are more coins to collect on this level than during Star 1. The time limit shouldn't be a problem on this level, but be careful not to die, as there are no mid-level checkpoints.

Star 5 (Purple Comet): Purple Coin Spacewalk
Available when a Purple Comet is in this Galaxy. Collect 100 Purple Coins within a 2 minute time limit. This purple comet mission is one of the easier levels, as the coins are in bunches of 10, making it very easy to get them. Just be careful to not fall on the way back to the start, where the Power Star appears.

Star 6 (Hidden): Yoshi's Unexpected Appearance
Enter Star 3. Proceed through the level as for Star 3. When you meet the Hungry Luma, feed it 50 Star Bits to create a new planet in the shape of Yoshi's head. Defeat all the Goombas on this planet to gain the Star.

If you are able to lead all the Goombas to you, and jump onto all of them without touching the ground in between, the seventh and subsequent Goombas will give you a 1-Up.