A Launch Star is an object in Super Mario Galaxy and Super Mario Galaxy 2. It is very common. As the name suggests, it is used to launch Mario across great distances through space. In order to use it, Mario must use his Star Spin while within its boundaries. Launch Stars return as items in Super Smash Bros. Ultimate as throwing items. Their victim will be launched in the direction the user threw them. Unlike most throwing items, Launch Stars can affect their summoner. Rosalina also summons this item for her Up Special Move, where she launches out of it immediately. However, it sports a rainbow pattern as opposed to being orange like it was.
There is also a similar but weaker variant, the Sling Star.