NGC 7023 - Iris Nebula

NGC 7023 is a wonderful example of an open star cluster associated with a reflection nebula. It is located in Cepheus, about 3.5 degrees southwest of β Cep (Alfirk).

Visually, NGC 7023 is a fairly bright, irregularly-shaped reflection nebula surrounding a 7th magnitude star (HD 200775) that interferes with observations. Very dark lanes within the nebular glow may be discerned with careful viewing. The surrounding field has a dim glow from outlying sections of the nebula. NGC 7023 lies in a region of the Milky Way darkened by dust, within which the nebula is embedded.

Sometimes called the Iris Nebula, NGC 7023 is about 6 light-years across, and 1,300 light-years away. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative years. Central filaments of cosmic dust glow with a reddish photo-luminesence, as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Yet the dominant color of the nebula is blue, characteristic of dust grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted and fantastic shapes. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs.

There is also an open cluster of stars associated with NGC 7023, known as Collinder 427. This loose open cluster is located on the west side of the reflection nebula, within the dark region above the "petal" structure of the Iris.