The Origin of Emission Lines
The spectra of the purely gaseous nebulae are completely different from the spectra of their central stars. The discrepancy is expressed in the structure of the spectra itself as well as in the intensities in certain of its parts. In the visual band the spectrum of the nebula consists of a number of very intense emission lines with a hardly noticeable continuum. The spectrum of the central star-nucleus, on the other hand, consists of a powerful continuous background with hardly noticeable absorption lines or no absorption lines at all. The energy emitted by a nebula in different emission lines considerably exceeds the energy of the corresponding regions in the spectrum of the star-nucleus. Nevertheless, the luminosity of a nebula is entirely due to the radiation of its central star-nucleus.
KeywordsMagnesium Recombination Helium Stratification Expense
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