Cave Nebula in SHO (SH2-155) - also known as Caldwell 9, is a diffuse nebula found in the constellation Cepheus. It is actually a part of a much larger complex of nebulae n the region which includes the emission, reflection, and dark nebulae. The designation indicates that this part of the Sharpless Catalog of emission nebulae which are located north of the declination -27 degrees. Sh2-155 is located 2400 light-years away and is an ionized HII region with evidence of star formation activity. The top edge of the cloud is illuminated by several hot, massive (OB) stars that are part of the Cepheus OB3 association. Sh2-155 lies at the edge of the Cepheus B cloud (part of the Cepheus
molecular cloud), and is
ionized by young stars from the Cep OB3 association. It has been suggested that radiation from the hot
O-type star HD 217086 is compressing the region, triggering the formation of a new generation of stars. A study of the region's
young stellar objects by the
Chandra X-ray Observatory and
Spitzer Space Telescope shows a progression of stellar ages in front of the cloud, supporting the hypothesis of
triggered star-formation.
This image was taken with my trusty 115mm Orion EON APO and QHY268M/Astrodon 3nm Narrowband filters in the Hubble palette.
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