This emission nebula in the constellation Swan has a central star (Walf-Rayet star) that is about 5 times brighter than our sun. It is at the end of its life and is already shedding its outer shells. This is the prelude to its end - a supernova.
The matter ejected from the star is strongly ionised by the star (the blue-grey veil in O3) and heated. This matter hits the matter in front of it and pushes it, causing it (red in the image, H alpha) to hit the interstellar medium at about 2,000 km/s and be heated further. This creates these shock waves with the characteristic structure.
|Object:||NGC6888 Crescent Nebula|
|Distance:||4,400 light years|
|Optics:||Askar 500, 500mm, f/7,5|
|Mount:||Skywatcher EQ8 on concrete pier|
Antlia ALP-T Dualband Filter
|Exposures:||65 x 300s, total 5h 25min|
|Guiding:||WO Uniguide 50, ASI290mini|
Editing in PixInsight only