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.

Colors
There are many Lumas of many colors
 * Yellow: Yellow Lumas transform into Sling Stars and are the most common variety. A few yellow Lumas can transform into Launch Stars as well
 * Blue: Blue Lumas transform into Pull Stars, and a large Light Blue Luma hosts the Luma Shop.
 * Pink: Pink Lumas known as Hungry Lumas transform into planets or galaxies, and create pink Launch Stars. Others transform into pink Launch Stars on the Observatory Grounds.
 * Green: Green Lumas are the guardians of the Trial Galaxies and transform into green Launch Stars
 * Red: Red Lumas guard Red Stars, which transform Mario into Flying Mario.
 * Purple: Lubba (The king of all Lumas) is the owner of Starship Mario. Another is a Luma that holds the power to move Prankster Comets.
 * Cream: Luma (The only cream Luma) gives Mario the power to Star Spin.
 * Black: Polari (The only black Luma) is seen in each of the observatories, and shows Mario the map.
 * Orange: Co-Star Luma is P2 once the second Wii remote is turned on. There's also another Luma who tells you about Co-Star Luma.

Super Mario Galaxy
The Lumas appear in ''Super Mario Galaxy, living on the Comet Observatory with Rosalina, and supporting Mario with his journey to save Peach.

In the end, all the Lumas sacrifice themselves to destroy the massive black hole created by Bowser's dying sun. However, Luma is reborn and lives on a small planet, while it is hinted that all of the other Lumas will be reborn later.

Mario Kart Wii
In Mario Kart Wii, a Yellow Luma is around Rosalina at all times, but it has no effect on gameplay.

Super Mario Galaxy 2
In Super Mario Galaxy 2, the Lumas serve a similar role as to the prequel. However, the purple Luma is absent, there are now Giant Lumas which are simply overgrown Yellow Lumas, there is an orange Co-Star Luma which acts as Player 2, and the Green Lumas just simply look forward to seeing the Green Power Stars.

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.
 * Luma's name may be derived from the first two letters of Mario and Luigi's names, Luigi and Mario.