This object, the 7th in the
Abell catalog, is a very faint ancient planetary nebula located 1,700 light-years away in the southern constellation of Lepus at a declination of -16 degrees. The nebula width in our apparent view is 13 arc-minutes, which corresponds to a diameter of 7 light years. Such a diameter is huge for a PN.
The central progenitor star (WD 0500-156) is the faint bluish star in the center of the nebula.
Although the magnitude of this PN, at 15, may seem fairly bright, that brightness is spread over a large area, making the surface brightness of this PN very dim.
While the cyan OIII signal is stronger overall here, especially in the central region, the reddish HII signal is more interesting. These two HII regions appear to me to be ansae, the result of polar outflows, since they lie on opposite sides of the nebula equidistant from the progenitor star. My collection of similar
PNe ansae is here.
If you scan through my
collection of ancient PNe, you will see that most of them have develop deformed edges or rim features from their long encounter with the surrounding ISM. Abell 7 is the largest planetary nebula which does not show signs of interaction with the surrounding interstellar medium, still having an almost perfectly spherical extent.
The background contains many colorful stars and a few distant galaxies.
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