Galaxy

From the Super Mario Wiki

Mario approaching a Galaxy with the use of a Launch Star.

A Galaxy is an enormous system consisting of gases, stars, Planets, and Comets. Mario visits many galaxies in his adventures through Super Mario Galaxy. The galaxy named Grand Finale Galaxy is home to Mario's planet (Mushroom World), while the Milky Way Galaxy is home to Earth ^[1]. The galaxies in Super Mario Galaxy are notably much smaller than real galaxies, often being comprised of nothing more than a few small planetoids.

[edit] Comets

Comets are a major feature of galaxies. Essentially, they are small clusters of matter floating through space, with a glowing tail created by solar radiation. In the Mario series, a comet can have an effect over the whole galaxy such as making cosmic clones of a person. These are special comets known as Prankster Comets. In the Super Mario Bros. Movie it was mentioned that an asteroid (a comet lacking a tail) killed off all the dinosaurs on Earth.