About 45 years later, Gustav Kirchhoff and Robert Bunsen noticed that several Fraunhofer lines coincide with characteristic emission lines identifies in the spectra of heated chemical elements. They inferred that dark lines in the solar spectrum are caused by absorption by chemical elements in the solar atmosphere. Their observations were in the visible range where the strongest lines come from metals such as Na, K, Fe. In the early work on the chemical composition of the sun the only elements that were detected in spectra were hydrogen and various metals, with the term metallic frequently used when describing them. In contemporary usage all the extra elements beyond just hydrogen and helium are termed metallic.