The Bubble Nebula also known as NGC7635, is about 7,100 light years away. The nebula is about 6 light years wide. It is caused by a star 40 times more massive than the sun blowing material into space, and slamming into the nebula around the star, shaping it into a bubble. It is in the Cassiopeia constellation. The nebula is an emission nebula. Discovered in 1787 by William Herschel. Also known as Sharpless 162 or Caldwell 11.