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Spectral Lines

History, Spectrographs, Doppler Shift

A spectral line is light of a single frequency, or wavelength, which is emitted by an atom when an electron changes its energy level. Because the energy levels of the electron vary from element to element, scientists can determine the chemical composition of an object from a distance by examining its spectrum. In addition, the shift of a spectral line from its predicted position can show the speed at which an astronomical object is moving away from Earth. The measurement of spectral lines is the basis of much of modern astronomy.

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Science EncyclopediaScience & Philosophy: Adam Smith Biography to Spectroscopic binary