In this and other similar emission nebulae , energetic ultraviolet light from an embedded hot young star strips electrons from the surrounding hydrogen atoms . As the electrons and atoms recombine they emit longer wavelength, lower energy light in a well known characteristic pattern of bright spectral lines . This image of the nebula was taken using a filter to select only light near the H-alpha wavelength. It shows those regions with substantial emission from atomic hydrogen . The relative strength of this emission can trace the densities of atoms within the gas cloud.
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