The HII region RCW 51 surrounds the massive young (8-9 million years) star cluster NGC 3293 and both in turn appear to be located in a similar distance and direction as the giant molecular cloud
Sodroski 62.
Kharchenko lists 16 ionising B-class stars as probable members, the hottest of which is the B0 Ia supergiant
HD 91969. She gives a distance of 2471 parsecs and an age of 8.7 million years. The entire complex lies near the
Car OB1 association.
I've sometimes referred to this striking cluster/nebula combination as the Eye of Horus. You can view a
more detailed image of the cluster here.
The cluster is NGC 3293, distance is d = 2750 +/- 250 pc, nuclear age is 8 +/- 1 Myr[
1]
Kharchenko catalog. [
2]
Notes
1. ^ Baume, G., Vázquez, R. A., Carraro, G., et al. (2003). "Photometric study
of the young open cluster NGC 3293", Astronomy and Astrophysics, Vol. 402,
549-564. [2003A&A...402..549B]
2. ^ 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]