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 7 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 phase. 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. This impact results in the bubble shape in this image. This is an 18 hour exposure through narrowband filters taken November 8-17, 2015. Click on the image for a larger view.