The Ghostly Galaxy is a galaxy in Super Mario Galaxy. It is located in the Kitchen and the second encountered. Its unlocking criterea is to get 20 Power Stars, including the Grand Stars in Bowser Jr.'s Robot Reactor and Bowser's Star Reactor. The galaxy is ghost themed and the boss is Bouldergeist. Luigi makes his first appearance in this galaxy.
Luigi and the Haunted Mansion
At first, Mario starts off on the Toad Brigade's Starshroom, but he has to use a Launch Star to reach the pathway into the mansion. Pumpkin Heads litter the pathway. Boos are inside the first room of the mansion, but a switch activates a swinging beam of light. Mario has to lure the Boos into the light to defeat them and get the items they hold. One of the Boos has a key which Mario can use to make his way deeper into the mansion. Further into the mansion, there are Star Chips to collect to rebuild a Launch Star, which appears in a window. Using the Launch Star, Mario is launched into another part of the mansion, where Luigi is calling for help. However, a window makes it impossible to help Luigi. Mario finds another way inside, where he discovers a new power-up, the Boo Mushroom. As Boo Mario, he needs to vanish to pass through the bars, but he must be careful of a beam of light which will make him turn back to normal. Mario needs to return to normal before he can speak with Luigi to get the Power Star.
A Very Spooky Sprint
In this level, Mario must blast to the edge of the galaxy and race the Spooky Speedster.
Beware of Bouldergeist
Mario is informed by a member of the Toad Brigade that Luigi has been kidnapped by "the monster that lives up ahead". Mario will have to find his way to a circular stone platform and then meets Bouldergeist, a ghost with the ability to control stone. Bouldergeist does not move, but can use his telekinetic powers to throw rocks. Mario will have to defeat Bouldergeist with Bomb Boos, exploding them on him three times in a row, then on the red part of his body, constituting the boss's weak point. The second "round" is even harder, because Bouldergeist will now create two stone hands for protecting him in case of Bomb Boos incoming, causing his hands to be hurt instead of the monster himself but even if they were destroyed, it will regenerate them. After his weak point is hit again, it explodes, leaving behind a Power Star.
Bouldergeist's Daredevil Run (Daredevil Comet in Orbit)
Very similar to Beware of Bouldergeist, however Mario starts on the boss planet with a maximum health of 1. This mission, until completed, is only available while a Daredevil Comet is in orbit.
Purple Coins in the Bone Pen (Purple Comet in Orbit)
Mario starts off on a small planet with the "Bone Pen" in front of it. The Bone Pen features bones as walls, meaty bones as bumpers, spiky balls as obstacles, and Pull Stars for getting around. There are more than 100 Purple Coins, but 100 have to be collected by Mario before the Power Star appears in the center of the pen. This mission has a one minute time limit. This mission, until completed, is only available while a Purple Comet is in orbit.
Matter Splatter Mansion
A hidden mission similar to the Matter Splatter Galaxy. While playing the level "A Very Spooky Sprint", the first planet, which contains Pumpkin Heads, also has two breakable stalagmites. One contains a Rainbow Star, and the other contains a Launch Star to the Matter Splatter Mansion. Platforms and rooms only exist when a sort of spotlight comes over them. Mario will need to go through, getting keys and unlocking doors, until he reaches a Power Star behind one of the doors.
This planet is the planet that is right after the Starting Planet. It is ringed shaped and contains Pumpkin Heads and Spiders (the amount depends on what mission it is). The starting planet has a creepy tree and two stalagmites (one containing a Rainbow Star and one hiding a Launch Star). The planet is connected to the Mansion Planet by bridge. In the second Mission, Mario needs to use Pull Stars, since he can no longer cross the bridge.
The mansion planet is the largest planet in the galaxy and Luigi is temporarily held there. It appears on the Galaxy Icon.
This area is visited in the third mission. Mario must make his way to the top to proceed.
This is where Bouldergeist lives. He appears when you get in his arena. When he materializes, the stairs leading to his battlefield collapse. This means you cannot backtrack when or after he is fought.
Phantom Hole Planets
These planets are hollow and are riddled with holes, hence their name. One has its own gravity because it has a small bouncy core at the centre. That one has Floating Mines, however.
Star Peace Spouting Planets
These planets are normally out of reach since they are not meant to be interacted with. However, they do spit out 5 Star Bits out of their top when they are passed.
Boo Race Zone
Mario and the Spooky Speedster race in this area. It is visited in Mission 2 and in the Purple Comet mission. At the endpoints are two round planets.
- Oddly, in the mission Purple Coins in the Bone Pen, there are only 149 Purple Coins, even though the Toads say that there are 150.