Sharpless 154 & 155 (Sh2-154 & Sh2-155)

Common Name: Cave Nebula (Sh2-155)

Also Known as: Caldwell 9 (Sh2-155)

Object Type: Diffuse Nebula

Constellation: Cepheus

Distance from Earth: 3,260 Light Years (Sh2-154) .... 2,400 Light years (Sh2-155)

Apparent Magnitude: 7.7 (Sh2-155)

Coordinates: RA 22H 51M 51.97S DEC 61 deg 13 min 29.5 sec (Sh2-154) ....RA 22H 57M 17.14S DEC 62 deg 28 min 33.4 sec (Sh2-155)

Actual Size: 70 light years in diameter (Sh2-155)

Apparent Dimensions: 50 arc-minutes x 30 arc-minutes (Sh2-155)

Discovered by: Sh2-155 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: Sh2-154 and Sh2-155 are diffuse nebulae in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity.
Sh2-155 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.
Sh2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs (2400 light-years) from Earth.
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.
The open cluster NGC 1470 is closeby.

Click Below Image(s) for Full Size:

Although Sh2-154 and Sh2-155 are relatively faint for amateur observation, some of its structure may be seen visually through a moderately sized telescope under dark skies.

Plate Solved Image

Sharpless 154 & 155 (Sh2-154 & Sh2-155)

Imaging Details
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