Bubble Nebula NGC 7635
NGC 7635 is also called the Bubble Nebula, Sharpless 162, or Caldwell 11. It is a H II 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, 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.
The central star BD+60°2522 is thought to have a mass of about 44 M☉, that is 44 times the mass of our sun.
The nebula was discovered in 1787 by William Herschel.
Source: en.wikipedia.org/wiki/NGC_7635 - 18.11.2017