Fraunhofer lines, (C) Wikipedia

Spectral absorption lines of the spectrum of the sun, named after the German physicist Joseph von Fraunhofer (1787–1826)
Such Lines are produced whenever a cold gas is between a broad spectrum photon source and the detector.
Photons are absorbed and then re-emitted in random new directions. Therefore the intensity in the original direction is lower and a dark line appears in the spectrum.