Dreadnought Galaxy

The Dreadnought Galaxy is a galaxy in Super Mario Galaxy. The galaxy is a mechanical and technological battle station. Topmaniac, the leader of the Topman Tribe, is fought here again. The galaxy reuses several elements from the Battlerock Galaxy, such as Cannons, Mines, and other battle operations, as well as music, but is based in and around a massive spaceship known as "The Dreadnought".

Planets/Areas
NOTE: Unless otherwise noted, all names are unofficial.

The Dreadnought
The Dreadnought is the spaceship that makes up most of the Dreadnought Galaxy. It has cannons and spikes that can damage Mario, causing him to lose one Health Point. At the top of the Dreadnought, there is a pool of water. There are also Springs and Pull Stars littered all over.

Beam Planet
The Beam Planet is a planet shaped like an hourglass that is full of electric beams and other electrical hazards that spin around it. At the opposite end is a Launch Star that Mario must get to by jumping on a spring.

The Dreadnought (Inside)
The entrance has three Goombeetles and a Warp Pipe. The inside portion is a side-scrolling area with hazards such as Amps, Cannons, and moving walls. At the end is another Warp Pipe. The gravity of this area can be changed with Gravity Arrows, which are necessary to proceed through the area. In the purple coins mission, after collecting the last purple coin, they land here, while the Goombeetles and the entrance pipe (along with its case) were replaced by a Gearmo who awards the player a star if he/she collects all of the purple coins.

Tower Planet
The Tower Planet is a planet consisting of various cylinders that fall when Mario gets to a higher level. On the top parts are a pair of moving walls and a Launch Star.

Aqua Planet
The Aqua Planet is a medium-sized planet with a Bill Blaster and several Goombeetles. There is a vault that when broken, floods the planet, which is necessary to complete the level. There are also a lot of platforms with lasers that move across the water and a pair of Robot Turtles that take Mario from platform to platform. Above it is a small cubical planetoid. Some metallic structures are above the water, and one of them has a Power Star.

Chibi Wanwan Path
This area has three parts. In the first part is a screw that moves forward or backwards depending on how much weight is on it. Beneath it is a green platform with Bob-ombs. The second part has several Flipswitch Panels which Mario must press by avoiding the Chibi Wanwan that constantly fall from the dog shacks. If he presses them all, Mario can access the third part. In this part are two more screws and two Octopodes that must be defeated, causing a Launch Star to appear.

Cannon Fleet Path
This is a section on the side of the Dreadnought which consists of several platforms of different sizes that travel along a path. There are obstacles such as cannons and electric currents. At the end is a Power Star.

UFO
The upper part of this UFO has a Green Topman and the lower part has a Warp Pipe that leads to the Garbage Dump. The Topman is needed to reach a Sling Star above.

Ammo Depot
This is a planet shaped like half a sphere. It is inhabited by a Gearmo that cleans the garbage. There are also some Bob-ombs that Mario must use to blow up the garbage in order to obtain a Power Star from the Gearmo.

Sphere Planet
This planet has several cylinder structures sticking out. Mario must knock two Spiky Topmen into an electrical barrier to free a trapped Luma. After being freed, the Luma will transform into a Sling Star that will lead Mario to the Cube Planet.

Cube Planet
This is a small planet shaped like a cube. There is a Ground Pound switch that makes five blue Star Chips appear. A Spring Topman is also found here, as well as a Spiky Topman in the "Topman Tribe Speed Run" level. The player must use the Spring Topman to get one of the Star Chips here.

Artillery Walls
The Artillery Walls are two walls that face each other located in the Dreadnought. The cannons shoot Cannonballs, and there are Pull Stars in the middle. There are also Mines in the way that can be taken out with a Star Bit. Mario has to avoid the cannonballs while traveling by them.

Landing Platform
This is a long, zigzagging landing platform with Montys, Treasure Chests and Spiked Sentry Beams that shoot electric waves at Mario. White circles around the Sentry Beams indicate how far out from the center the electric waves can go. Near the end of the platform is a Launch Star. There is also a Koopa Troopa whose shell can be used to break open the treasure chests to collect their contents.

Topmaniac's Saucer
This saucer is similar to the one in Battlerock Galaxy. There are a lot of Spiky Topmen in it, and there are also many electric currents that block Mario's path. At the top is Topmaniac, waiting to be fought.

Trivia

 * This is the only galaxy in the game to have different starting planets for every mission. In fact, all of the starting planets seem to be in the same location, as those for other missions are never visible in a mission and they replace one another.
 * The UFO in this galaxy resembles the one Bowser uses to remove Peach's castle from its foundation and into outer space in the opening cutscene.