description Sh2-155 Overview
Sh2-155, also known as the Cave Nebula, is a dark emission nebula located within the Cepheus B cloud approximately 2,400 light-years from Earth. This Caldwell 9 H II region exhibits ongoing star formation and displays a distinctive cave-like structure due to dense dust clouds. Astronomers and researchers studying stellar nurseries and galactic structures find Sh2-155 particularly noteworthy for its complex morphology and active regions of creation.
help Sh2-155 FAQ
Why is Sh2-155 called the Cave Nebula?
A bright ionized rim beside a dark dust cloud creates the appearance of a cave mouth. The nickname refers to that visual boundary within a larger complex containing emission, reflection, and dark nebulosity.
Are Sh2-155 and Caldwell 9 the same object?
Yes, Sh2-155, Sharpless 155, and Caldwell 9 are catalog names for the same star-forming region in Cepheus. Stewart Sharpless included it as object 155 in the second edition of his H II-region catalog in 1959.
How far away is the Cave Nebula?
Published estimates commonly place it around 2,400 to 3,000 light-years from Earth. The difference reflects the difficulty of defining and measuring structures within the larger Cepheus B cloud complex.
Can the Cave Nebula be seen through an amateur telescope?
It is a difficult visual target because its light is diffuse and low in contrast, despite an integrated magnitude near 8. Astrophotographers can reveal much more structure using long exposures and narrowband filters sensitive to hydrogen emission.
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