NGC 7635
Emission Nebula in The Constellation Cassopeia

NGC 7635, also called the Bubble Nebula, Sharpless 162, or Caldwell 11, is a H II region emission nebula in the constellation Cassiopeia.  It lies 7,100 light years distant from our Sun, and close to the direction of the open cluster Messier 52.  The "bubble" is approximately 10 light years wide and is created by the stellar wind from a massive, hot, 8.7 magnitude young central star SAO 20575.  The nebula is near a giant molecular dust and gas cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow around the bubble.  The "bubble" portion of the nebula is colliding with this molecular cloud on one side, and unevenly.  This collision is slowing down the bubble's expansion and may eventually deform its appearance or make it go away completely in its current visual form as seen from here on Earth.   It was discovered in 1787 by Friedrich Wilhelm Herschel. The star SAO 20575 is thought to have a mass of at least 10 times our own Sun, and is approximately 4 times the diameter of our Sun.

Image Information  Courtesy of  Wikipedia

Image Details:

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  • Instrument:  TMB 152 triplet apo refractor @ f/8 (1200mm)
  • Mount:  Astro-Physics P1200GTOCP3
  • Image Scale:  1.58 arc-seconds per pixel after processing
    Camera: SBIG ST-2000XM with AO8 Adaptive Optics and CFW10 Color Filter Wheel using Custom Scientific LRGB filters 
    Filters & Exposure Times:
    • L:  24 x 5 minutes binned 1 x 1
    • R:  20 x 5 minutes binned 2 x 2
      G:    9 x 5 minutes binned 2 x 2
      B:  18 x 5 minutes binned 2 x 2
      Hydrogen-alpha:  6 x 20 minutes binned 1 x 1
    • Multiple Luminance Layering in Photoshop (technique as described by Rob Gendler)
    • Total equivalent unbinned exposure time of 11.8 hours
    Software: Maxim DL/CCD, CCDStack, Adobe Photoshop CS2, RC Astro Gradient X-Terminator
    Location:  C.A.A.S. East Observatory, Little Rock, AR., El. 650ft
    Date: October 3rd, 2011

Wade Van Arsdale
Little Rock, AR., USA
November 23rd, 2011