NGC 7635 (Caldwell 11), the Bubble Nebula, is an emission nebula in the constellation Cassiopeia located at a distance of approximately 7800 light years. The relatively bright star at about the 11 o’clock position within the prominent bubble is known as BD +60°2522 or SAO 20575 and is the source of the bubble shape. The star is known as a Wolf-Rayet star, which is an O-type star that is nearing supernova stage. These stars blow off significant portions of their mass while in this stage. It has an enormous energy output and a powerful stellar wind which is impacting the molecular cloud surrounding the star.
