The Iris Nebula is so named because of its resemblance to the iris flower (
Iris germanica). It is a reflection nebula; the dramatic appearance of the glowing “petals” is due to extremely bright light from the central star cluster, NGC 7023, reflecting off the surrounding dust clouds. (One of the main culprits is the very hot and bright star, HD 200775, which so obviously dominates the cluster.)
Most of the reflected photoluminescence is blue, but there are some faint reddish and orange filaments, suggesting the presence of complex chemical compounds. The surrounding fields of interstellar dust are much cooler, hence brown, and some parts are so dense as to block out any background stars altogether and so appear black.
The Iris Nebula is about 1,400 light-years away, and the bluish petals are about 6 light years across. It is located in the constellation of Cepheus, which is one of the
49 classical constellations described by Ptolemy.
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