Wolf-Rayet bubbles are some of the most interesting subjects in the sky. Wolf-Rayet stars are very hot stars that are well advanced through their stages of life. When they enter this Wolf-Rayet stage, the stellar wind speeds up and eventually runs into the slower stellar wind from earlier in its life. The resulting shockwave can be spectacular!

In this case, for the Dolphin Head, that bubble appears to be mostly O-III. There is hydrogen alpha there but it is much fainter. You can see the faint read within the gaps of the O-III. But, it’s important to remember the levels they look in the image are indicative of their relative levels in reality. I’ve boosted the hydrogen (red) to help it stand out. In reality, it’s even fainter than it appears here.

This nebula has been on my bucket list for imaging ever since I learned of it but it’s taken a while to get to it, but it was worth the wait!

The nebula is about 4,500 light years away in the constellation of Canis Major.

This is 42h 24m of HOO data. For all the technical details, see astrobin.