Abell 39 is a spherical planetary nebula about 7000 light years from us in the constellation Hercules. It represents the fate of stars like our Sun, which are not massive enough to supernova in their old age, so instead eject much of their mass into space. The bright edge of the nebula is about 5.2 light-years in diameter, but an
image using a 0.5 m telescope with 111 hrs of exposure actually shows the faint outer halo extends to at least 9.7 light-years. The nebula has been expanding for an estimated 22,000 years. Interestingly, the central star (a subdwarf O star with surface temperature over 8800K) is about 0.1 light-year left of center, thought to be due to an asymmetrical ejection of mass from the star. Note the east edge is brighter than the west, and details within the nebula are not symmetric either.
I saw Adam Block's amazing
image earlier this year with the 0.8 m Schulman Telescope, which made me think this would be a wonderful, but difficult target, for me to attempt. Even the brighter parts are very faint, visible only in my imagination in a 20 second sub with my L-eNhance duo narrow band filter, so this project took more time than I had planned--and indeed, could have used more integration. In the end, I am very pleased with the result, though my plate scale doesn't come close to a 0.8 m telescope, so the small galaxies in and around the nebula are not resolved as they were for Adam. However, I was very pleased with the nebula, I did capture the details, which are quite large (just of low contrast), and I even captured at least some of that very faint halo, which is not apparent in Adam's image. I hope you like it.
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