NGC7635 Bubble Nebula; Cassiopeia
Astro Systeme Austria N12 f/3.5 astrograph
STL-11000M
H-alpha 140 minutes
June 2007; Inkom, ID
Comments: Unlike many other circular nebula, which are called planetary nebulae, the Bubble Nebula was not formed by the death of a star, or nova. Rather, this amazing nebula is actually a cavity in the larger HII region. It was created when a hot blue star's radition sweeped away the surrounding gas and dust leaving a hollow cavity. The "wind" created by the central star sweeps the dust ahead of it at an astonishing 2000 km/sec creating a visible shock wave.
The Bubble Nebula is approximately 7,100 light-year distant.
