This Sharpless HII emission nebula is located 15,000 light years away in the constellation of Scutum at a declination of -13 degrees. It spans 15 arc-minutes in our apparent view, which corresponds to a width of 70 light years. It is a rarely imaged target - the only other image of it that I have seen is by
Jerry.
This region is located only 1 degree northeast of M16 and lies just outside of the extent of the nebulosity of the M16 area.
Sh2-53 appears to be comprised of numerous HII regions – perhaps 5 or 6. I find it interesting that so many HII emission nebulae appear to be comprised of multiple, closely spaced, mostly spherical objects, the most famous example being
NGC 6334. I don’t know if such closely related objects are interdependent, or if the sources are simply clustered, or if it is just visual superposition.
Stewart Sharpless created the Sharpless catalog of HII regions (emission nebulae) in 1959. The list is intended to be comprehensive north of declination −27°. Almost every object on the list begins with the prefix Sh2, perhaps because the final list of 313 objects is his second catalog. There are two Sh1 objects which were not included in the updated Sh2 catalog because they were discovered not to be emission regions by that time. My collection of Sharpless objects is shown
here.
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