Sh 2-308 Dolphin in Canis Major

The Dolphin Nebula is the remnant of shells "blown out" by a Wolf-Rayet star, that is, a hot, young, massive blue star. It is located 4,500 light-years from Earth. It shines primarily in the lines of ionized oxygen OIII and hydrogen Ha. It took a long time to capture it in these lines so that the silhouette of the nebula would appear against the RGB background.