NGC7538 HSO

NGC 7538 is an emission-reflection nebula in the constellation Cepheus. It is located approximately 9,100 light-years from Earth. It is part of a vast complex known as the Cassiopeia OB2 association, named for the cluster of young, hot O and B class stars, which also includes emission nebulae (formed by the ionization of hydrogen by the radiation of hot stars), dark clouds, star clusters, and reflection nebulae.

NGC 7538 is sometimes called the Northern Lagoon Nebula or the Little Lagoon Nebula. Its distinctive feature is that it contains the largest known protostar to date, known as NGC 7538S — a stellar embryo whose mass already exceeds 100 solar masses and which is surrounded by a huge accretion disk, about 300 times the size of our Solar System.

The image was obtained by combining stars captured with RGB filters and the nebula captured with Ha, OIII, and SII filters.
During processing of the nebula, the Ha filter image was used in the red channel, SII in the green, and OIII in the blue.