Cave Nebula
NGC 3626
Properties
Position & Identifiers
Visibility
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About Cave Nebula
Description
The Cave Nebula (Sh2-155) is an emission nebula and dim HII region in Cepheus, about 2,400 light-years away. It lies at the edge of the Cepheus B molecular cloud and contains active star formation.
Observing Tips
A challenging visual target requiring dark skies and at least an 8-inch telescope. An OIII or UHC nebula filter is essential. The nebula appears as a faint, irregular glow with a dark intrusion. Best observed in autumn evenings when Cepheus is near the zenith.
History
Cataloged by Stewart Sharpless in his 1959 catalog of HII regions as Sh2-155. The name "Cave Nebula" comes from the dark lane that appears to cut into the bright emission region.
Fun Facts
The Cave Nebula sits at the boundary between a hot ionized bubble blown by massive stars and a dense molecular cloud. This interface triggers new star formation.
Community Photos (1)
Credit: Hewholooks. License: CC BY-SA 3.0. (Wikimedia Commons)
Skybred Mar 2, 2026