Abell 7 is a very faint planetary nebula in the constellation Lepus. It also goes by the designations PNG 215.5-30.8 and PK215-30.1. It was discovered by George Abell in 1955. Abell 7 is very faint and is listed as visual magnitude 13.2. It's a bit oblong and I measured its size as 12.7 x 13.8 arc minutes. Abell 7 is estimated to be 20,000 yrs old and lies at a distance of 1800 light years. Abell 7 was formed as many planetary nebula when the central star met its end of life and shed its outer layers of gas into space. The central star,WD0500-156, is now a blue white dwarf with an estimated age of 10 billion years.
The image was taken with RGB and 5nm Ha and OIII narrow band filters. Abell 7 has a outer shell of red hydrogen emission and an inner shell of mainly blue-green OIII emission with a bit of very faint Ha emission. Although faint it's quite a striking and beautiful planetary nebula. There is also a very faint band of background Ha emission which goes from left to right across the field of view.
Also within the image field are many small and faint galaxies. In the high res or zoomed in views you can see PGC 16611, a mag 15 galaxy just to the upper right of Abell 7. Another interesting galaxy is the long and thin IC400 which is listed as mag 15.2 or 17.57 depending upon which reference you look at. It lies just below and to the left of Abell 7. Lastly a nice but small (1 arc min) spiral galaxy, mag 14.31 PGC 16581 is in the upper right. Can you find them in the high res view?
The image combines 44.6hrs of exposure time which lasted from 24 Jan 2023 thru 26 Feb 2024.
Above is a cropped view in high res that shows the beautiful Ha and OIII emission that makes up this planetary nebula. The glowing clouds of HII emission are quite striking.
Annotated image showing the many faint PGC galaxies near Abell 7.
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