Planetary nebula PN G081.1-03.9 in NHO

[iansmith]

Also known as IPHASX J205527.2+390359 it canbe found in the constellation of Cygnus.

In this image north is to the right and east is to the bottom. The insert shows the PNe at x2 the original.

This little PNe appears as #141 in the 1st release of the IPHAS catalogue of new extended PNe published in Jul 2014 by L.Sabin, Q.A.Parker,R.L.M.Corradi, et al.
(https://academic.oup.com/mnras/article/443/4/3388/1019117) This paper publishes the results of a survey of new PNe extracted from the much larger IPHAS catalogue. IPHAS stands for the Isaac Newton Telescope  Photometric Ha survey of the Northern Galactic Plane. 

The image is composed of N2 for the red, Ha for the green and O3 for the blue channels for the nebulosity. The starts are LRGB, where the luminance was taken from a combination of the narrow band channels.

This PNe does not make many appearances in the professional literature with only 3 entries in SAMBA, one of which is the paper referenced above.
Another paper, https://academic.oup.com/mnras/article/470/3/3707/3869624, suggests that PNe such as PN G081.1-03.9 have a higher H2 molecular content than narrower waisted PNe, but the reasons for this are unknown. On the sky the PNe is only 23” across. This paper gives it a diameter of 2.74 light years at a distance of 28,050 light years, so it’s actually quite a large structure (compare to the Dumbbell nebula which has a diameter of 2.88 light years).

PN G081.1-03.9 is a bipolar PNe with an open barrel structure with the tips protruding slightly from the ends of the barrel. I have tried to bring out some of the inner structure inside the barrel. 

The bright pink arc at the bottom of the central ring structure, in my image, appears to be an N2 feature. The rest of that ring is, I think, Ha but covered by O3 emission, so it takes on a bluer appearance. The O3 forms a brighter central oval of material inside the barrel, that covers this ring and is also coincident with the central portion of the Ha.

The Ha extends below the N2 to the east (bottom) of my image and extends slightly to the west (top) as well but is generally quite diffuse. There also some knots of material in the arcs to the east and west in both the N2 and Ha.

The Ha is brighter in the central regions compared to the eastern and western arcs, which ties in nicely with the general observation that the broad ring PNe have brighter H2 emission in the central regions compared to their lobes. The H2 tends to be confined to the edges of this region, with more ionised material closer to the central star. This suggests that the ionised H is protecting the molecular H gas.