by Rod Pommier
Telescope: Celestron Compustar C14 with 0.75x focal reducer (f/8.3). Camera: SBIG STL 11000M with Baader Planetarium H-alpha, L, R, G, and B filters. Location: Pommier Observatory, Portland, OR, USA. Dates: Various between 2011-10-25 and 2012.-08-14. Exposures: HaLRGB=240:335:60:60:60 = 12 hours: 35 minutes total exposure.
The Bubble Nebula lies not far from the open cluster M52 in Cassiopeia. The bubble is formed by stellar winds from the hot magnitude 8.7 central star pushing out material in the large molecular cloud within which the star formed. The star appears off center within the bubble because the nebula is denser on one side than the other, resulting in asymmetric expansion. Intense UV radiation from the star causes the surrounding nebula to glow, particularly at the hydrogen-alpha wavelength.