Sh 2-155 (also designatedCaldwell 9,Sharpless 155 orS155, orLBN529) is adiffuse nebula in the constellationCepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. It is widely known as theCave Nebula, though that name was applied earlier to Ced 201, a different nebula in Cepheus. Sh 2-155 is an ionizedH II region with ongoingstar formation activity,[1] at an estimated distance of 725 parsecs (2400 light-years) from Earth.[2][3]
Sh 2-155[4] was first noted as a galactic emission nebula in 1959 in the extended second edition of theSharpless catalogue,[5] being a part of the much larger Cep OB3Association.[5] Although Sh 2-155 is relatively faint for amateur observation, some of its structure may be seen visually through a moderately sized telescope under dark skies.[6][7]
Amateur photograph of the Cave Nebula in theHubble palette
The name "Cave Nebula" was coined for this object byPatrick Moore, presumably derived from photographic images showing a curved arc of emission nebulosity corresponding to a cave mouth.[12] The name was also used earlier to refer to another brighter but unrelated reflection nebula in Cepheus known as Ced 201[13] or VdB 152,[14][15] positioned atR.A.: 22h 13m 27sDec.: +70° 15′ 18″ (2000). The name's application to Sh 2-155 has come into vogue through the nebula's inclusion in Moore'sCaldwell catalogue[16] as object Caldwell 9. (SIMBAD lists the name for Ced 201, but not for Sh 2-155.)[4][13]
^Getman, Konstantin V.; Feigelson, Eric D.; Townsley, Leisa; Broos, Patrick; Garmire, Gordon; Tsujimoto, Masahiro (2006). "ChandraStudy of the Cepheus B Star-forming Region: Stellar Populations and the Initial Mass Function".The Astrophysical Journal Supplement Series.163 (2):306–334.arXiv:astro-ph/0601405.Bibcode:2006ApJS..163..306G.doi:10.1086/501453.ISSN0067-0049.S2CID16305023.
^Panagia, N.; Thum, C. (1981). "A study of the S 155A – CEP B cloud and its relation to Cepheus OB3 association".Astronomy and Astrophysics.92 (2):295–299.Bibcode:1981A&A....98..295P.
^Minchin, Nigel R.; Ward-Thompson, Derek; White, Glenn J. (1992). "Carbon monoxide and far-infrared observations of the S 155-Cepheus B region".Astronomy and Astrophysics.265 (2):733–742.Bibcode:1992A&A...265..733M.
