NGC 7635 The Bubble Nebula
NGC 7635, also called the Bubble Nebula, Sharpless 162, or Caldwell 11, is a H II star forming region emission nebula in the constellation Cassiopeia. It lies close to the direction of the open cluster Messier 52. The "bubble" is created by the stellar wind from a massive hot, 8.7 magnitude young central star, the 15 ± 5 M☉ SAO 20575 (BD+60 2522). The nebula is near a giant molecular cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow. It was discovered in 1787 by William Herschel. The star SAO 20575 or BD+602522 is thought to have a mass of 10-40 Solar masses.
This Hubble palette image was taken with a William Optics FLT132 at F5.6; QSI683-wsg ccd; 10 Micron GM1000HPS mount and Astrodon 5nm NB filters. The image comprises 3 x 1200s each of Ha, OIII & SII giving a total integration of 9 hrs. October 2016.