This nebula is ionised by the O9V class Sherwood 182 (
[F89b] S74 1). It is either at the same distance as the powerful radio source
W 50, or sits in front of it, depending upon the authority.
Both W 50 and Sh 2-74 can be seen in this
radio image. This image suggests that W 50 is a distinct object but might be joined to Sh 2-74 by a spur visible at radio frequencies.
The microquasar
SS 433 is part of W 50. This bizarre object, also called
V1343 Aquilae, is spewing out two jets of material at more than one-quarter the speed of light.
Ionised by the O9V star Sherwood 182. [
1]
More on SS 433. [
2]
W 50 and Sh 2-74 are both located at about 3000 parsecs. [
3]
Notes
1. ^ Forbes, D. (1989). "Photometry and spectroscopy of stars in northern H II
regions", Astronomy and Astrophysics Supplement Series, Vol. 77, 439-445.
[1989A&AS...77..439F]
2. ^ Wang, Z.-R., McCray, R., Chen, Y., et al. (1990). "The infrared knots
around SS 433", Astronomy and Astrophysics, Vol. 240, 98-104.
[1990A&A...240...98W]
3. ^ Elston, R. & Baum, S. (1987). "High-resolution radio observations of W50,
the remnant associated with SS 433", The Astronomical Journal, Vol. 94,
1633-1640. [1987AJ.....94.1633E]