Anders Jonas Ångström and the foundation of spectroscopy — Commemorative article on the second centenary of his birth

• Ångström's work on solar spectroscopy highlights his relevant role in the evolution of this discipline.
• Ångström's contributions to different scientific disciplines in physics are detailed.
• Ångström's work was pioneer in the determination of precise lines' wave-lengths for some chemical substances.
• Ångström's and Kirchhoff's achievements are complementary in the evolution of concepts related with light absorption.
• Using of appropriate instruments were decisive for Ångström's success in spectral studies.

The Swedish astronomer Anders Jonas Ångström, born two centuries ago and professor of physics at Uppsala University, was one of the founders of optical spectroscopy. By using diffraction gratings out of glass plates with fine scorings across the face, he was able to observe the spectrum of the Sun, announcing in 1862 that he had discovered the lines of hydrogen in the solar spectrum. His most important work, “Recherches sur la Spectre Solaire”, including an atlas of close to a thousand spectral lines, became the standard of spectroscopy for at least a quarter of a century. This article deals with his life as well as his main contributions to the development of several areas of physical science, stressing his pioneer activities in spectroscopy.