Abell 43 (or PK36+17.1) is a planetary nebula about 8500 light years away in Ophiuchus. I have not seen any name for this nebula, but to me it looks like a knobby string-filled
Ball of Twine. From expansion rate data, the Ball of Twine is about 25,00 years old and is currently about 20 light years across, to us about 1.3 minutes in angular extent.
The most scientific interest in this planetary nebula is that the very hot (117,000 K) progenitor star has six low amplitude pulsations with periods between 2380 s and 6075 s, see:
Abell 43: Longest period Planetary Nebula Nucleus variablehttps://arxiv.org/abs/0705.2115. It is known as a PG 1159 star, generally found in planetary nebula. Fair warning, I’m not an expert on these hydrogen-deficient pulsating stars, but my understanding is the pulsations are driven by the odd property that the star gets increasingly opaque when their temperature rises, so heat has a harder time escaping, thus heating it further. This makes the star somewhat unstable. This is known as the kappa-mechanism, and in these stars is caused by partial ionization of carbon and oxygen.
For this image, I started with my L-eNhance filter, but when I got my new L-eXtreme I switched to that filter. My stacking used 2X drizzle, but then the final raw image was binned 2X—I find this improves resolution somewhat while still retaining the original S/N. The stars and nebula were processed separately—the nebular twine was brought out with AFP-R (used by NASA as a multi-scale unsharp masking tool), followed by the very gentle noise reduction of NoiseXterminator.
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