NGC 6914 nebulae, optical image. The red parts of this mixed nebula are emission nebulae, clouds of hydrogen gas that glow red as the gas is ionised by radiation from the hot young stars within them. The blue parts are reflection nebulae, gas and dust clouds that do not emit their own light, but instead reflect the blue light from the stars in and around them. Dark areas are dark nebulae; gas and dust clouds that do not emit or reflect light and are seen only because they block the light from stars and nebulae behind them. The NGC 6914 complex lies around 4000 light years from Earth in the constellation Cygnus.