Both Sharpless and Avedisova list the O9 class multiple star HD 24431
as the main ionising star for the large diffuse Sh 2-205, sometimes called the Peanut nebula. Avedisova also lists two cooler B-class ionising stars.
A recent series of papers divides the nebula into three distinct regions (although at similar distances), with the B-stars ionising a different region than HD 24431. They also suggest that CY Cam (HD 24094
) may be an O8.5 or O9 star instead of the usually suggested much cooler B8 and may be the main ionising star of LBN 148.11-0.45 (LBN 696
) in this direction.
A 2011 paper states that CY Cam is a B1 III giant.
Like Sh 2-202, this nebula lies at the edge of the Cam OB1
This false-colour hydrogen-alpha image
reveals that Sh 2-205 is the brightest region of an even larger nebula.
You can see an infrared image here
and a false colour visual frequency image here
Sh 2-205 was the subject of two recent papers, which divide the nebula into three distinct regions although at similar distances, with the B-stars ionising a different region than HD 24431 and adds CY Cam (HD 24094) as a potential ionising star. [1
CY Cam is a B1 III giant. [3
A 2001 paper lists the O8 star HD 24451
as the main ionising star for Sh 2-205 instead of HD 24431. This appears to be an error, however, as SIMBAD says that HD 24451 is a K-class star in quite a different direction. [4
1. ^ Romero, G. A. & Cappa, C. E. (2008). "Sh2-205 - I. The surrounding
interstellar medium", Monthly Notices of the Royal Astronomical Society,
Vol. 387, 1080-1092. [2008MNRAS.387.1080R]
2. ^ Romero, G. A. & Cappa, C. E. (2009). "Sh2-205 - II. Quiescent
star-formation activity", Monthly Notices of the Royal Astronomical
Society, Vol. 395, 2095-2102. [2009MNRAS.395.2095R]
3. ^ Tetzlaff, N., Neuhäuser, R., & Hohle, M. M. (2011). "A catalogue of young
runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the
Royal Astronomical Society, Vol. 410, 190-200. [2011MNRAS.410..190T]
4. ^ Zdanavicius, J., Cernis, K., Zdanavicius, K., et al. (2001). "Photometric
Classification of Stars and the Interstellar Extinction near the
Camelopardalis and Perseus Border", Baltic Astronomy, Vol. 10, 349-373.