The Space Junk Galaxy is a galaxy in the game Super Mario Galaxy. It is the first galaxy in the Fountain and has a space/futuristic theme. Like its name implies, the Space Junk Galaxy contains lots of discarded space junk, including old rocket ships, floating debris, and various other objects and platforms. A lot of the objects are silver or blue, and there is a spaceship in it.
The Pull Star is used much more than in the other known galaxies. Also, Toads in the Toad Brigade are on a big platform covered in crystals; if Mario frees the Toads trapped in the crystals, the main Starshroom will appear with a Launch Star that he can use to go to the next location. There is also a wooden planet shaped like Yoshi's head.
The last unique feature of this galaxy is that it has a path that builds itself when Mario approaches it, but crumbles after he leaves. This is later re-used in Bowser's Galaxy Reactor, except the path crumbles after a few seconds automatically.
Pull Star Path
As the name suggests there are a lot of Pull Stars, which Mario must use to make his way through the Galaxy. At the end Mario has to get 5 Silver Stars on a place full of small bits of path, which join together to make a path for Mario to go across.
Kamella's Airship Attack
Tarantox's Tangled Web
Mario must traverse various planets until he finally break open Tarantox's planet and fight him. Sling Pods are first seen here.
Pull Star Path Speed Run (Speedy Comet in Orbit)
This mission is only accessible, unless already completed, if a Speedy Comet is in orbit. Mario must go through Pull Star Path under a time limit.
Purple Coin Spacewalk (Purple Comit in Orbit)
Mario must collect 100 Purple Coins in the area at the end of Pull Star Path. The coins come in bunches of 10 on several platforms. It is also timed. This mission is only accessible, unless already completed, if a Purple Comet is in orbit.
Yoshi's Unexpected Appearance
After Mario feeds a Hungry Luma, it turns into the Yoshi Head Planet. On this planet, Mario must defeat all the Goombas to get the Power Star to appear. A counter is kept for the number of times Mario jumps on Goombas consecutively and if the count goes over 8 Mario will get 1-Ups.
The Starting Planet is a square planet whose top surface Mario starts his trek through the galaxy on. It has all-around gravity and slightly resembles the landing planet in the Space Junk Area.
Hence their name, these Planets are three spherical glass planets. There are three Amps moving around them. These planets have a ring of metal around their surface and two metal plates on either side. There are five Star Chips moving about on these planets. After collecting the Star Chips, Mario can use a Launch Star to go to the Rocket Planet.
The Space Ship is a "planet" whose loot consists mostly of just coins. It is a big, long, red-and-tan space ship floating around in space. A similar (although more damaged) rocket is encountered on the route to Tarantox. At the end of it is a Sling Pod along with a few Spoings. The ship is similar to Olimar's ship, possibly referring to the Pikmin series, but this has not been confirmed.
This planet is a T-shaped planet that resembles a tower. It contains some Spoings. It is also where Mario finds the Toad Brigade, all of them trapped in a Crystal. After Mario frees them all, the Starshroom will appear. Various items and a Goomba are also trapped in crystals. On the top of the Starshroom is a Sling Star, which will take Mario to the Space Junk Area.
Assembly Block Planet And Space Junk Area
The Space Junk Area contains the final planet of the Pull Star Path mission. There is junk platforms everywhere, and after making his way here, Mario needs to collect all 5 Silver Stars in order to make a Power Star and complete the mission. You can complete the mission by collecting the Silver Stars while the junk lets Mario stand on it. There is a very massive Black Hole under the platforms, and if you fall you get sucked into it. No matter how far you get away from the area by jumping or long jumping, the Black Hole will suck Mario and he'll lose a life or he gets a Game Over if he had 1 life left. This area also takes place on 2 comets, the Purple Comet and the Speedy Comet. Both of those comets have the really massive Black Hole, and the latter's maze is altered.
Kamella's Airship Fleet Area
Although it is bare in most areas, this area is infested with Airships during Mission 2: Kamella's Airship Attack. In this Mission, Kamella invades. She and the others supposedly retreat after this mission is completed, which may explain why it is empty.
Small Maze Planet
This of the Unknown Planets is a planet that is encountered shortly before the battle with Tarantox. At first, Mario walks on top of it, which is practically a transparent crystal orb. Once he finds the passageway in, he can go under the crystal layer and explore underneath, where 1-Up Mushrooms and other treats are waiting. Mario can also backtrack if it is his wish by jumping back out of the passage's entrance. There are also a few Star Bunnies underneath the crystal layer, who guide Mario through to the Launch Star.
Phantom Boss Spider Zone
Grave Stone A Planet
This planet is a planet mostly made of maroon, dark red, brownish rock. It has a sort of arch, as seen in the picture. This planet is an entrance to Tarantox's lair. The pre-boss music begins when Mario lands on this planet, and the spider's Sticky Planet is nearby.
The Rock Planet is the first planet in the game to have a Sling Pod and is the beginning of a long path of them.
Abandoned Rocket Ship
Just like the one in the first mission, here drifts a lonely rocket whose riders apparently died or abandoned ship. It is infested with spiders, but behaves otherwise like the first one. See above for more details.
Tarantox's Planet is exceptionally large and looks like a giant version of the top of a Sling Pod. In fact, Mario uses a Sling Pod to get to the planet, breaking its shell open and revealing a giant sticky spider web, where he fights Tarantox, who is frozen inside. It has outward gravity on the inside.
The Yoshi Planet is a planet in the shape of a large, wooden Yoshi head that shoots red steam out of its nostrils. It only appears in Yoshi's Unexpected Appearance. This appears to be the third reference to the Yoshi clan in Super Mario Galaxy, the first being the Yoshi game file icon, and the second the Yoshi Egg Planet that was shown earlier.