Bubble Nebula (NGC 7635) in Cassiopeia
About 1/2° southwest of the open cluster M52 in the constellation of Cassiopeia, one can find the emission nebula NGC 7635 known as Bubble Nebula and Caldwell 11. Like Thor’s Helmet (NGC 2359) or Crescent Nebula (NGC 6888), a Wolf-Rayet star is reponsible for the shape of this object. This star, BD 65 2522, the brightest star (8.5mag) within the bubble, is blowing away the interstellar material by its radiation power. The HII region itself is cataloged as Sharpless 162.
In this image, the Ha data was blended to the luminance channel only to preserve the natural colors as good as possible. North is about upper left of the image.