Sharpless 157, also known as the Lobster Claw Nebula, is a bright emission nebula in the constellation Cassiopeia. It lies just south of the better-known Bubble Nebula (NGC 7635). The predominantly yellow part of the nebula is a very large H II region that is ring-shaped by the stellar wind of several giant stars, including the bright and very young Wolf-Rayed star WR 57. The blue colored regions at the right part of the image mainly consist of highly ionized oxygen (OIII) and other gases.
NGC 7635, also known as the Bubble Nebula, Sharpless 162, or Caldwell 11, is an H II region emission nebula in the constellation Cassiopeia located about 7,100 light-years away. Its star burns a million times brighter than our sun and produces powerful gaseous outflows called stellar winds that howl at more than four million miles per hour. Over time, the winds have pushed nearby gas and dust outward, forming a layer around the star that’s denser in some areas than others. It was discovered in 1787 by William Herschel.