Sharpless 2-308 or RCW 11 is a large, faint ring nebula surrounding a Wolf-Rayet star (WR 6) in Canis Major.
WR6 is the bright, blue star near the center of the image and has been the subject of considerable research.
The large yellow star is Omicron 1 CM. The nebula has an age of 70,000 years and an expansion velocity of 60 km/s.
It is one of the closest WR stars to our solar system.
The bubble is large, taking up nearly 3/4 deg in this image, and is the result of fast WR winds sweeping through slower red supergiant winds.
The [OIII] signal dominates this structure (Seen in Greenish Blue - see next image for O3 only), whereas the H-a signal is comparably much weaker (Seen in Red).(APOD)
Imaged with the 16" f3.75 Dream Astrograph.
Apogee Alta U-16M camera.
O3 for 4 hrs (BIN 2)
Ha 60 min (BIN 2)
RGB 10 min per channel
Total of 5.5 hrs
Imaged from Tivoli farm in Namibia May 2015.