This huge almost circular nebula is very prominent in hydrogen-alpha as can be seen in this SuperCOSMOS image
Avedisova concludes that it is ionised by the O6 V star HD 167633
. Humphreys places this star in the Ser OB1
association in the Sagittarius arm.
However, several other sources give larger distance estimates, placing this nebula in the Centaurus arm, where it may be part of the Scutum supershell
SIMBAD associates Gum 79 with HD 167633, and this star is in the Scutum supershell region.[1
A 2010 paper associates Sh 2-44 with the infrared bubble [CPA2006] N14
The star cluster NGC 6596
appears in the direction of Sh 2-44. Kharchenko gives a distance of 1100 pc for this cluster, so it may be a foreground object. [3
1. ^ Callaway, Matthew B., Savage, Blair D., Benjamin, Robert A., et al.
(2000). "Observational Evidence of Supershell Blowout in GS 018-04+44: The
Scutum Supershell", The Astrophysical Journal, Vol. 532, 943-969.
2. ^ Deharveng, L., Schuller, F., Anderson, L. D., et al. (2010). "A gallery of
bubbles. The nature of the bubbles observed by Spitzer and what ATLASGAL
tells us about the surrounding neutral material", Astronomy and
Astrophysics, Vol. 523, A6. [2010A&A...523A...6D]
3. ^ Kharchenko, N. V., Piskunov, A. E., Röser, S., et al. (2005).
"Astrophysical parameters of Galactic open clusters", Astronomy and
Astrophysics, Vol. 438, 1163-1173. [2005A&A...438.1163K]