This object, known as the Dolphin’s Head Nebula and the Gourd Nebula, is a Wolf-Rayet emission nebula located 5000 light years away in the constellation of Canis Major at a declination of -24 degrees. The nebula spans 45 arc-minutes in our apparent view and is 60 light years in diameter.  Wolf-Rayet emission nebulae are some of the most beautiful objects in the universe, as shown by my poster of them.

The nebula is being blown out by fast winds from a hot huge 6.8 magnitude Wolf-Rayet star (HD 50896), the bright blue star near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of our Sun and are thought to be in a brief, pre-supernova phase. The gas in this nebula is primarily OIII gas.  

So many things grab my attention here:

- Although the nebula is roughly spherical, it is elongated along an axis that runs from bottom left to top right of the image. This is likely due to bi-polar gas expulsion from the opposite stellar poles.  The bulge at top right appears to be on the verge of breaking out.  Several other minor axes of gas expulsion are also seen here, particularly the small bumps at left and right.

- My favorite part of this object, aside from the overall shape, is how the OIII nebula is slightly larger in diameter than the HII nebula. This is seen in the image where the outer portion of the white nebula surface sits slightly inside the outer portion of the cyan oxygen surface. This is most obvious on the right side of the nebula.

- The red pattern of HII towards the top of the nebula is tough to understand.  Is it part of the nebula, or simply part of the background HII in the sky?  It seems like it is part of the background to me.

- The bright 3.9 magnitude orange supergiant star towards the bottom of the nebula is Omicron Canis Majoris (HD 50877). It is about 2500 light years away, about halfway between us and the nebula.  This cool (4000 K) star is about 8 times as massive as our Sun, 280 times its diameter, and shines with 16,000 times its luminosity.

- The small dim whitish perfectly circular object at the left edge of the nebula (9 o’clock) is the planetary nebula PN G234.9-09.7.  Little information is available for this PN. If it is the typical PN diameter of 2 light years, this PN would be about 2500 light years away, about the same distance away as the bright orange star.