The nebula shines because of the energy provided by the cluster of hot blue and white stars. However, these O and B stars are considerably heavier than our Sun, since they contain some thirty times as much matter, and this extra weight shortens their lifetime to just a few million years in total. The cluster also contains a large number of faint red stars, which are probably reddened by absorption in the dust surrounding them. M16 is in a late stage of its evolution, where the hot stars have blown away the closer material and now shine in a cavity surrounded by an expanding complex of neutral lumps, which show bright edges due to shock waves created as the outwardly flowing material hits other gas. M16 also contains many small black globules, which are believed to be compact dust clouds on their way to collapsing into proto-stellar objects, and then later into new stars.
Current estimates suggest that several new stars are formed somewhere in our Galaxy every year.
In fact, the current glowing red appearance and the dark features are, respectively, the gas and dust out of which the existing stars originally condensed. The nebula also contains some neutral gas clouds, which have no electrical charge and are only detected by radio astronomers.