Fraunhofer lines

Astron.

the dark lines of the solar spectrum.

[1830-40; named after J. von FRAUNHOFER]

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In astronomical spectroscopy, dark lines in a star's spectrum caused by selective absorption of its radiation at specific wavelengths by the various chemical elements in its atmosphere.

First observed in 1802, they are named for the German physicist Joseph von Fraunhofer (1787–1826), who from с 1814 plotted over 500 of them and designated the brightest with the first few letters of the alphabet. About 25,000 Fraunhofer lines are known to exist in the Sun's spectrum, between the wavelengths of 2,950 and 10,000 angstroms.

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▪ physics

      in astronomical spectroscopy, any of the dark (absorption) lines in the spectrum of the Sun or other star, caused by selective absorption of the Sun's or star's radiation at specific wavelengths by the various elements existing as gases in its atmosphere. The lines were first observed in 1802 by the English physicist William Hyde Wollaston but are named for the German physicist Joseph von Fraunhofer, who from about 1814 plotted more than 500 of them and designated the brightest by the letters A through G, a system of identification still in use. About 25,000 Fraunhofer lines are now known to exist in the solar spectrum, between the wavelengths of 2,950 and 10,000 angstroms. (One angstrom equals 10^-8 cm.)

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