Ghostly Galaxy

"We detected signs of Luigi in this galaxy! I hope he hasn't been eaten by ghosts!"

- Captain Toad

Ghostly Galaxy is a galaxy in Super Mario Galaxy. Many elements of this area are of a haunted theme, and Mario can find Boo Mushrooms that turn him into a Boo. This galaxy also has the first appearance of Luigi in the game, who is rescued in the process of obtaining the galaxy's first Power Star. After being rescued, Luigi will later discover a few more Power Stars for Mario to collect in other galaxies. Bouldergeist is the boss of this galaxy.

Boo Mansion Gate Planet
The starting point is a Green Starshroom, which has a Launch Star leading to the Boo Mansion Gate Planet. The starting planet has three bats and three Pumpkinhead Goombas. There is a spike that spawns a Rainbow Star when spun, which can be used for destroying the Chomps in the first mission. In the third mission, there are three Spranglers. Each mission has a different Launch Star to get to the planets. There is a big gap in the middle of the planet that contains a black hole.

Haunted Mansion
The Haunted Mansion is visited in two levels: Luigi and the Haunted Mansion and Beware of Bouldergeist, though Beware of Bouldergeist only has part of the mansion. In Luigi and the Haunted Mansion, a ray of light can be turned on by hitting a Lever Switch near the door to defeat a Boo. Also, there are some boxes near the edges of the room. Some of them contain Toads that give Mario information, while others give him Coins and Star Bits. There are also some Bowser statues near the crates.

There is a painting of a Boo on top of the stairs and when Mario goes near it, a Boo spouts out. A Launch Star leads to the upper floor of the mansion. Luigi is trapped in a prison and must be rescued. Jill Board teaches Mario how to use the Boo Mushroom in one of the rooms. In Luigi and the Haunted Mansion, there is a hidden room containing a large amount of coins. To enter this room, Mario needs to enter a Star Chip room containing Pumpkinhead Goombas. Then, Mario must go to the ceiling and he must ground pound a white circle full of cracks, where the hidden room gets revealed. The room consists of a Lever Switch that activates coins appearing temporarily and eight Sling Stars. The Sling Stars lead Mario to each other and they help him collect the coins.

In Beware of Bouldergeist, only the first part of the mansion with the Bowser statues is seen. Instead of a Boo painting however, there is a Bomb Boo painting. It is used to destroy the statues to get coins, or to destroy the statue in the fireplace to proceed onwards. There are also the boxes from the first mission. The fireplace contains a Launch Star.

Phantom Tower Planets
When Mario gets to the second Launch Star in Beware of Bouldergeist, he arrives at the first Phantom Tower Planet. This planet contains some Scuttlebugs, Pumpkinhead Goombas, Bomb Boos, and a few Sling Pods. At the top, there is a Sling Star that takes Mario to the second Phantom Tower Planet. Here, Mario must collect five blue Star Chips to create Pull Stars leading to a Launch Star. This takes Mario to the Phantom Hole Planet with a bouncy ball, then to the Bouldergeist Battle Planet.

Bouldergeist Battle Planet
The Bouldergeist Battle Planet is where Mario encounters Bouldergeist, a boss. This planet is shaped like a circle with platforms leading up to it. There is also Lumalee here. When Mario fights Bouldergeist, Bomb Boos appear. Besides them and a few coins, the planet is empty. When Bouldergeist is beaten, Mario earns a Power Star.

Boo Race Zone
The Boo Race Zone is where Mario races the Spooky Speedster using Pull Stars. It is ringed by bones and there are multiple obstacles made of bones all around it along with a cluster of mines at the end. This zone is also where Mario collects 100 Purple Coins in under one minute. This version of the Boo Race Zone is made up of Pull Stars and bones so the player does not get out of the boundaries. There is also some meat that bounces Mario in a different direction.

Phantom Hole Planets
The Phantom Hole Planets are just the hollowed out rims of a planet, one of them has a pink bouncy ball in its center and mines around it. Most of them do not have gravity barring the planet with the bouncy ball.

Darkness Room Planet
The Darkness Room Planet is an area very similar to the Matter Splatter Galaxy. It is apparently a crumbling mansion where Mario must follow spotlights of shifting matter to navigate through the mansion and get the Power Star.

Star Peace Spouting Planets
These are six small Star Peace Spouting Planets that shoot from three to five Star Bits each. Mario only passes by them and can only reach one of them by doing the Pull Star movement exploit glitch. They seem to be made of metal by close examination and are covered by a purple covering. If looked at closely, the player can see small red stars on them.

Planet Rocket
The Planet Rocket appears only in the Luigi and the Haunted Mansion level and the levels with Bouldergeist, and appears to be an exact replica of the planets of the same name from the Space Junk Galaxy. It has a similar appearance to Olimar and Louie's ship from Pikmin 2. Though it cannot actually be visited by Mario, the player can look to the left just after landing on the Haunted Mansion in order to see it floating in space in the Luigi and the Haunted Mansion level, and above and to the left of the Bouldergeist Battle Planet in the Bouldergeist levels. A large amount of debris circles the ship.

The player can only reach the ship via hacking. The ship has little gravity that can be escaped with a single jump.

Boo Race Start Planet
The Boo Race Start Planet is where the Spooky Speedster is found. It has multiple trees and all of the members of the Toad Brigade are there. There are several Star Bits in the trees, and the player starts the race with the Spooky Speedster here.

Boo Race Goal Planet
The Boo Race Goal Planet is a ringed planet where the race with the Spooky Speedster ends. The ring acts as a wall which does not let Mario get across. However, if Mario does a backflip, wall jump and spin backwards, he can make it over. Another way back to the starting line is to take the Warp Pipe at the top of the planet.

Blue Star Cupsule Planets
The Blue Star Cupsule Planets are two capsule-like planets in the middle of the Boo Race Zone. Their only feature is that they have Pull Stars in the middle of them that will let Mario go across.

Trivia

 * A remix of the music heard inside the mansion is used for Ghost Houses in Super Mario 3D Land. Additionally, in Paper Mario: Sticker Star, a small portion of the music was rearranged and is heard in The Enigmansion, and a faster version plays once all Boos are encountered in the dining room.
 * The first four notes of the music that plays in this galaxy spells D-E-A-D.
 * Ghostly Galaxy's background, along with a couple others is actually a slightly edited version of that of the Ghost Ship from The Legend of Zelda: The Wind Waker.