Still catching up on my processing queue from last season.
This narrowband image with RGB stars captures a series of deep sky objects in the constellation of Cassiopeia at a declination of +61 degrees.
The largest object in this image is Sh2-157, nicknamed the Lobster Claw nebula. This bright emission nebula is located 8000 light-years away and is over 200 light-years across. This nebula has been described as a ring nebula surrounding the Wolf-Rayet star WR 157. WR 157 is a member of the Markarian 50 star cluster. WR 157 is the brightest star at the center of this image:
Although I can see the emission fronts expanding from the WR 157 source star, the surrounding structures are very complex and it seems a bit simplistic to me to just describe this fascinating object as a ring nebula.
The most striking object in this image is NGC 7635, the Bubble Nebula, which is located about 7,000 light years away. Although it looks small in the image, the bubble diameter is about 7 light years across. A closeup image of the Bubble is shown here:
This object is caused by a stellar wind emitted from the source star (another Wolf-Rayet star). These WR stars expel a significant amount of mass, resulting in the expanding gas bubble which is contained by the molecular cloud which surrounds it.
Several additional deep sky objects are also seen in the image:
Open star cluster M52:
Open star cluster NGC 7510:
Planetary nebula KjPn 8:
Emission nebula NGC 7538:
Emission nebula Sh2-157:
Emission nebula Sh2-156 (IC 1470):
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