Rosalina is a character who made her debut appearance in the game Super Mario Galaxy. Rosalina first appears in the Gateway Galaxy, and she is also the adopted mother of the Luma. Rosalina commands the Comet Observatory. She is a very powerful figure, as her duty is to watch over and protect the cosmos as well as the Luma.
Rosalina's back-story is chronicled in a storybook told by her in the Comet Observatory's Library in Super Mario Galaxy. Nine chapters are unlocked throughout the game, and the last is unlocked by completing the game. During the story, Rosalina mentions her home planet as "a blue planet"; Earth is also known by this name, so it is possible Rosalina comes from Earth.