NGC 7635, also known as Bubble Nebula, is an hydrogen structure surrounded by a vast and dense nebular region in the proximity of the constellation Casiopea. The name "Bubble" comes from its round shape created by the stellar wind emitted by the young star that lies at its core.
NGC 7635 is 11000 l.y. from the Solar System and extends "just" 5 l.y. across.