Why do dark Fraunhofer lines appear in the Sun’s spectrum?

Dark Fraunhofer lines appear in the Sun’s spectrum due to the selective absorption of radiation at specific wavelengths by various elements existing as gases in the solar atmosphere.1

These dark absorption lines are produced by transitions of electrons within atoms or ions. As electrons move between different energy levels, they absorb energy in the form of light at specific frequencies. In the Sun, as radiation travels from the interior toward the surface, these atoms in the cooler, outer layers of the solar atmosphere absorb specific wavelengths of the outgoing light, resulting in the characteristic dark lines observed in the solar spectrum.21

The identification and study of these lines, first plotted extensively by Joseph von Fraunhofer, laid the foundation for modern spectroscopy, allowing astronomers to determine the chemical composition of the Sun and other stars.13