Sh 2-154 is ionised by the B0 III giant LS III +60 28
, according to Avedisova. She places the nebula in the star formation region SFR 108.96+1.59
along with a molecular cloud.
According to a 2000 paper, radiation from stars associated with Sh 2-154 may be accelerating a giant molecular cloud that appears to contain 700 solar masses of carbon monoxide and perhaps 10 thousand solar masses in total viral mass.
The molecular cloud mentioned by Avedisova in association with Sh 2-154 appears to be [YDM97] CO 45
from the position and bibliographic reference she provides. However this cloud, which contains 200 solar masses of radioactive 13
CO, has an estimated distance of 730 parsecs. [1
] This may be a case where the photometric distance to the ionising star is larger than the kinematic distance of the surrounding gas.
Sh 2-154 is associated with a giant molecular cloud that appears to contain 700 solar masses of carbon monoxide and perhaps 10 thousand solar masses in total (viral mass). It is possible that this cloud is found within the Cepheus molecular clouds and only appears to be further away because the gas has been accelerated by star formation within the cloud.[2
1. ^ Yonekura, Yoshinori, Dobashi, Kazuhito, Mizuno, Akira, et al. (1997).
"Molecular Clouds in Cepheus and Cassiopeia", The Astrophysical Journal
Supplement Series, Vol. 110, 21. [1997ApJS..110...21Y]
2. ^ Ungerechts, H., Umbanhowar, P., & Thaddeus, P. (2000). "A CO Survey of
Giant Molecular Clouds near Cassiopeia A and NGC 7538", The Astrophysical
Journal, Vol. 537, 221-235. [2000ApJ...537..221U]