This area lies just on the border between the constellations Cassiopeia and Cepheus. M52 (upper left corner) is a fine open cluster located in a rich Milky Way field. The distance of this cluster is not very well known, measurements indicate something between 3.000 and 5.000 light years.
Situated about 35 arcminutes southwest of M52 is the Bubble Nebula NGC 7635 around the 7th-mag star HD 220057. Within the diffuse emission nebula lies a dark inclusion which appears as a faint and diffuse oval, about 3.5 x 3 arcminutes in size, hence the name "Bubble Nebula". The bubble was probably formed when the nebulous material inside it was blown out by stellar wind of the bright OB star HD 220057. It is difficult to see because of its low surface brightness.
Scattered around M52 and NGC 7635 are several other patches of nebulosity. Near the right edge NGC 7538 is located, another small and quite bright emission nebula. The large nebula near the lower right edge is Sh2-157, a faint emission nebula looking somewhat like a claw. The brightest part of it is designated Sh2-157a (the slightly brighter knot embedded within the nebulosity).
M52 and NGC 7635 - Bubble Nebula Region, Wright-Newtonian photograph.
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