Sh2-308 surrounds the Wolf–Rayet star WR 6, also known as EZ Canis Majoris. The star’s extremely fast wind is colliding with material expelled during earlier stages of its life, sweeping that older gas into an enormous expanding shell.

The nebula is especially rich in emission from ionized oxygen, which often gives the shell a luminous blue-green appearance in narrowband images. Its faint, nearly circular structure spans a surprisingly large patch of sky even though the central star itself appears ordinary at a glance.

The shell is blown by WR 6, also known as EZ Canis Majoris, a Wolf–Rayet star shedding mass through an extraordinarily fast stellar wind. That wind sweeps surrounding material into a huge expanding bubble whose oxygen emission is especially strong along the thin outer rim. The nebula is therefore a snapshot of a massive star actively reshaping the interstellar medium shortly before the end of its life.

The Dolphin Head lies in Canis Major, the Great Dog. Greek traditions commonly place the constellation beside Orion as one of the hunter’s dogs, with brilliant Sirius marking the animal’s most prominent star.

The nebula’s dolphin nickname is modern and comes from its photographic outline rather than ancient lore. It creates a playful contrast: a sea creature hidden within a constellation long imagined as a celestial dog.

Canis Major is often identified as a hunting dog following Orion across the winter sky. Another later story associates the constellation with Laelaps, the unbeatable hound that could catch anything it pursued. The modern “Dolphin Head” nickname has no connection to that ancient canine imagery; it comes entirely from the bubble’s photographic shape, adding a new visual story inside an old constellation.