M13
NGC 7635, The Bubble Nebula
The very interesting object NGC 7635 also known as the "Bubble Nebula", for its resemblance to its namesake, is actually an emission nebula, not a planetary nebula as some may think.  It is an emission nebula in that it generates its own light from a nearby star that excites hydrogen atoms to emit light.  In contrast, planetary nebula, named because they sometimes resemble planets, are expanding shells of gas given off by a dying star.  The Bubble Nebula's central star is not dying, on the contrary it is a young vibrant star.  Emission nebula are often known as HII regions and associated with the birth of new stars.  In this case the central whitish star SAO20575, clearly visible, is producing a significant amount of stellar wind pushing against the interstellar material to form a bubble in space.  The star is also causing the material to glow as well as reflect its own light.  The nearby surrounding red region is also an HII region being excited by the same young star.  The nebula is about 7000 light years away toward the constellation Cassiopeia, the vain, mythological Greek queen, who boasted about her unrivaled beauty.   Certainly, the Bubble Nebula is a beauty.
Optics: RC Optical System 20" F/8.2 (4165.6 mm Focal Length) Date: July - Oct 2015
Camera: SBIG STXL-11000 with Adaptive Optics Location: Columbus, Texas
Exposure: LRGB = 300:80:60:80 minutes Imager: Kent E. Biggs