Caldwell 9

Common Name: Cave Nebula

Also Known as: Sharpless 155 (Sh2-155)

Object Type: Diffuse Nebula

Constellation: Cepheus

Distance from Earth: 2,400 Light years

Apparent Magnitude: 7.7

Coordinates: RA 22H 57M 17.14S DEC 62 deg 28 min 33.4 sec

Actual Size: 70 light years in diameter

Apparent Dimensions: 50 arc-minutes x 30 arc-minutes

Discovered by: Sh 2-155 was first noted as a galactic emission nebula in 1959 in the extended second edition of the Sharpless catalogue, being a part of the much larger Cep OB3 Association.

Description: Sh 2-155 is a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity.
It is widely known as the Cave Nebula, though that name was applied earlier to Ced 201, a different nebula in Cepheus.
The name "Cave Nebula" was coined for this object by Patrick Moore, presumably derived from photographic images showing a curved arc of emission nebulosity corresponding to a cave mouth. The name was also used earlier to refer to another brighter but unrelated reflection nebula in Cepheus known as Ced 201.
Sh 2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs (2400 light-years) from Earth.
Sh 2-155 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.

Click Below Image(s) for Full Size:

Although Sh2-155 is relatively faint for amateur observation, some of its structure may be seen visually through a moderately sized telescope under dark skies.

Sharpless 155 (Sh2-155) Cave Nebula Nebula

Imaging Details
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