In this image north is to the bottom and east is to the left.

For the nebula, the narrow band channels had the stars removed, then masked stretched to the same b/g value and independently processed before being combined according to the following PixelMath formula:

• Red = N2, Green = Ha, Blue = O3.

The background stars are broadband only and processed separately. The broadband images were combined to create n RGB image, from which the nebula was removed. They were then processed separately before being combined with the narrowband only image to create the picture you see above.

This is quite a bright nebula and I could probably have gotten away with 5 minute exposures, but since I have calibration files for 10 minute ones, I stuck with that.

Assuming a distance of 2,200 light years, the PNe is approximately 0.5ly across (not including the halo) and only ~1000 years old. On the sky, the brighter part is about 26” x 24”.

This nebula has two points of interest. Firstly, it is a nice example of a triple shelled PNe, and it also has a large outer spherical halo. Secondly, there are the two bright spots lying either side of the central star. These are examples of FLIERS: Fast Low Ionisation Emission Regions. They appear to be relatively young and moving outward at supersonic speeds. However, their shape would suggest that they are stationary, relative to the expanding nebula gasses that flow around them.

Inside the giant halo is a three shelled structure, that contains approx. 0.5 solar mass of material. The multiple shells suggest multiple events during the relatively short life of this PNe. In my image we see the central star, surrounded by a bright, elliptical shell of material. Around this is a much fainter shell, who’s edge I have emphasised to make it a little more obvious and to highlight its apparent connection to the FLIERS. Surrounding both of these is another shell, dimmer than the first shell, but brighter than the second shell.

It is though that this central star had (still has?) a companion that influence the shape of the PNe. A companion is a common way to create these sorts of elliptical PNe. However, its mass and separation are constrained by a curious feature of the large halo. If you look at the north-eastern edge of the halo, there is a bright knot of material with a small amount of flattening of the halo’s sphere. There is a similar flattening on the opposite side. These two deviations from a true sphere put constraints of the companion stars size and separation. The companion star may have been a brown dwarf which then accumulated some of the material from the central star and went on to influence the shape of the nebula. Or it could have been a larger star that was partially or completely destroyed by the expulsion of material from the progenitor star. It’s also possible that this interaction gave rise to the two FLIERS either side of the central star.

The edge of the halo provides us with another mystery. Why is it bright? The PNe lies high above the plane of the Milky Way, so the interstellar medium here should not be very thick, which would allow the gas from the star to just fade away. If ISM could is thin, then the bright edge could be due to ionisation of the halo gas, brought about by a shock wave from faster material compressing the gas. Or it could be that the ISM is dense in this part of the Milky Way, causing the halo gasses to pile up.

All in all, quite a mysterious object.