The Bubble Blast Galaxy is a galaxy in Super Mario Galaxy. It is one of the Trial Galaxies. The stage is similar to Bubble Breeze Galaxy (where the player puts Mario into a bubble, and then gets across the stage by blowing the bubble around until it gets to the other side; aka Bubble Blowing), but much harder, mainly because of the many more hazardous objects that can get in the way if not controlled correctly.
The whole stage takes place in the middle of space, with a Black Hole right below it. Therefore, if the player hits a hazardous object which will pop the bubble Mario (or Luigi) is in, Mario will immediately fall into the Black Hole, resulting in starting over the stage.