Fraunhofer lines. Illustration of the Sun's spectrum, showing a set of dark absorption lines known as Fraunhofer lines. These are named after the German physicist Joseph von Fraunhofer (1787-1826), who discovered them in 1814. The spectrum is shown ranging from blue (left) to red (right), with the wavelength in nanometres across bottom. The absorption lines indicate the presence of certain elements in the Sun's atmosphere.