Transcript: Isaac Newton was the first to take a prism and disperse the Sun’s light and show that it was composed of a smooth spectrum of radiation from blue to red wavelengths. We also know that the Sun emits invisible electromagnetic waves at infrared and ultraviolet wavelengths. The smooth, continuous radiation of the Sun is a thermal spectrum with a peak wavelength that Wien’s law tells is associated with a temperature of about 5,700 Kelvin. In the early nineteenth century the German physicist Joseph Fraunhofer used higher dispersion to show that the Sun’s spectrum was crossed by a series of dark absorption lines. He compared the positions of wavelengths of these absorption lines to the spectrum of hydrogen measured in the laboratory. The wavelengths matched exactly showing a chemical fingerprint in the Sun of the element hydrogen and that the Sun was mostly made of hydrogen.