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| Most photographs of regions of the nebulae around star-forming regions show that the red nebulosity is associated with one or more very hot, bright stars; these same stars are responsible for the ultra-violet radiation which splits the hydrogen atoms apart. In addition to the deep red colour, other wavelengths contribute to the overall hue. Most prominent are lines in the blue part of the spectrum and blue light scattered by the dust particles which are almost always associated with gas clouds in the Galaxy. The normal colour of a star-forming region is therefore usually magenta, a bluish-red colour, the exact shade depending on the amount of blue light present. The star-forming nebulae NGC 6334 and 6357 pictured here straddle the Galactic plane and are seen through thick dust which absorbs blue light, giving them an unusually ruddy hue. |