NGC7635 Bubble Nebula

The Bubble Nebula is a fascinating object and is justifiably famous.  The nebula resides about 7100 light years from Earth in the constellation Cassiopeia, and was discovered in 1787 by William Herschel.

The oval “bubble” in the center of the image is formed by the powerful stellar wind from the gigantic young O-type star SAO 20575 (BD+60°2522), which is seen within the bubble in the upper right quadrant in this image.  This star is only about two to four million years old (sources vary), a tiny fraction of the age of our Sun at about 4.5 billion years.  But this “baby star” is a monster, with 44 times the mass, 15 times the radius, and 398,000 times the luminosity of our Sun.

The bubble, which is about 10 light years across, is formed as a shock front, as the extremely hot gas at the surface of the star escapes as a stellar wind (traveling at 1800-2500 km/s), which pushes cooler interstellar gas against the giant molecular cloud of hydrogen gas and dust in the vicinity.  The denser material of the cloud forms a barrier to cause the edge of the bubble shape to form.  Meanwhile, radiation from the star is exciting the hydrogen gas in the molecular cloud so that it emits radiation, mostly in the H-alpha region of the spectrum.

About this image:  This is the first image with my new ZWO ASI6200M camera and Chroma filters, and I am very pleased with the data I was able to acquire with this setup.  I faced fewer image processing challenges than with the old SBIG 11000M CCD camera and filters I used for several years.  The image was composed of data from Red, Green, Blue, and H-alpha filters.  The H-alpha data, which was quite prominent, was mapped to the red channel in image processing, which resulted in the dominating red color throughout the nebula.  I avoided mixing H-alpha data into the star colors, so those are just RGB.  I chose to crop the image to enlarge the bubble, but have also uploaded the full frame version of the image.