Luma

Lumas are star-like creatures that appear in Super Mario Galaxy. Unlike most Stars, they have a tear drop-like shape, and come in many colors. They are much like Power Stars, but they are more circular in shape and able to talk. Lumas boast the ability to transform, from minor objects to entire galaxies. They seem to acknowledge Rosalina as their "mama". Most of them make their home in the Comet Observatory.

Only one cream-colored Luma is seen; he is known as Luma, although the Luma that transformed into the comet that Rosalina and the Lumas travel on appears to be cream-coloured in Rosalina's storybook's illustration. He is the Luma that Rosalina gives Mario in the beginning of the game. Luma grants Mario the power to do Spins. Yellow Lumas transform into Sling Stars and are the most common variety. A few yellow Lumas can transform into Launch Stars as well. Red Lumas guard Red Stars. Green Lumas are the guardians of the Trial Galaxies and transform into green Launch Stars. Blue Lumas transform into Pull Stars, and a large Light Blue Luma hosts the Luma Shop. There is also another type of Luma that are pink in color, known as Hungry Lumas. The last type of Luma is a purple Luma that holds the power to move Prankster Comets.

In the end, all the Lumas (including "the" Luma) are sucked into the massive black hole created by Bowser's dying sun. However, Luma is reborn and living on a small planet while it is hinted that the other Lumas will be reborn later.

In Mario Kart Wii, a Yellow Luma revolves around Rosalina at all times. It has no effect on gameplay.

In the Super Mario Galaxy 2 trailer, when Mario performs a Spin, Luma comes out of his hat to participate, like he did in the original Super Mario Galaxy. As of yet, it is still unknown is more Lumas will appear in Super Mario Galaxy 2.

Trivia

 * Paper Mario featured a similar species, called Star Kids. Like the Lumas, the Star Kids were young stars, who were raised on a special place to become real stars someday. They also possessed magical abilities, like the Lumas, and a very similar, childish behavior.
 * The name Luma comes from the Latin lumin, which means "light." It is a reference to their similarity to the Power Stars and their future as stars. A Luma was spotted on Mario and Sonic at the Olyimpic Winter Games which means Rosalina might be in the game. (nope)
 * Although the Luma that appears next to Rosalina in Mario Kart Wii is a Yellow Luma, Polari was usually the Luma at her side in Super Mario Galaxy.