The Collaborative International Dictionary
Fraunhofer lines
Fraunhofer lines \Fraun"ho*fer lines`\prop. n. pl.. (Physics.) The lines of the spectrum; especially and properly, the dark lines of the solar spectrum, so called because first accurately observed and interpreted by Fraunhofer, a German physicist.
Wikipedia
Fraunhofer lines
In physics and optics, the Fraunhofer lines are a set of spectral lines named after the German physicist Joseph von Fraunhofer (1787–1826). The lines were originally observed as dark features ( absorption lines) in the optical spectrum of the Sun.
Usage examples of "fraunhofer lines".
They looked exactly like what the astronomers called Fraunhofer lines, when the only way they had to know what a star or planet was made of was to study it through a spectroscope.