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