LBN 251, also known as The Longhorn, is an emission nebula in Cygnus. The nebula is dimmer than other nebulae in Cygnus, and is therefore observed primarily through long-exposure photography. It is part of the Cygnus molecular cloud. The nebula is ionized by nearby stars, however it is not itself a star-forming region. The nebula is internally divided into two clouds, divided by cold dust.
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