Located in the constellation of Cassiopeia, it is a vast star-forming region approximately 300 light-years across, composed mainly of ionized hydrogen, which emits its characteristic red light, mixed with oxygen, sulphur and cosmic dust.

At its centre lies the open cluster Melotte 15, formed by young (1.5 million years old), massive stars whose radiation and stellar winds shape the gas and dust into pillars and cavities, while also triggering the birth of new stars.