Gustav Kirchoff, Robert Bunsen

Kirchoff’s Rules of Spectroscopy A hot solid or liquid body produces a rainbow or continuous spectrum. A hot but low-density gas emits a spectrum of lines that is characteristic of the gas. This emission spectrum or bright-line spectrum can be used to identify the gas, since it’s unique, like a fingerprint. If a continuous spectrum or rainbow of colors passes through a cooler low-density gas, the gas will absorb the very same colors that it would have emitted if it were hot. This absorption spectrum appears as a series of dark lines on top of a rainbow. The spectrum of a star is an absorption or dark line spectrum.

This is the spectrum of the sun. It is a dark-line or absorption spectrum.