Red Power Star
From the Super Mario Wiki
The Red Power Star is a power star in Super Mario Galaxy. It can be located in the Gateway Galaxy after Mario passes through the Gate in the Comet Observatory. There Mario can find Rosalina, as well as a Red Luma, who allows him to use Red Stars to become Flying Mario, so that he is able to collect one-hundred Purple Coins. Upon doing so, the Red Power Star appears for Mario to collect.
After collecting the Red Power Star, Mario has access to Red Stars in the Comet Observatory, and is able to fly around the place at his leisure. Other than those mentioned, the Red Power Star has no other special attributes.