His combination of the spectroscope with photography for the study of the solar system resulted in proving that the sun contains hydrogen. He published his extensive research on the solar spectrum in Recherches sur le spectre solaire (1868), including detailed measurements of more than 1000 spectral lines.
In a paper presented to the Stockholm Academy in 1853, he not only pointed out that the electric spark yields two superimposed spectra, one from the metal of the electrode and the other from the gas in which it passes, but deduced from Leonhard Euler's theory of resonance that an incandescent gas emits luminous rays of the same refractive capacity as those which it can absorb. This statement, as Sir Edward Sabine remarked when awarding him the Rumford medal of the Royal Society in 1872, contains a fundamental principle of spectrum analysis, and though for a number of years it was overlooked it entitles him to rank as one of the founders of spectroscopy.
His son, Knut Johan Ångström (1857-1910) was known for his research at Uppsala University on solar radiation, the radiation of heat from the sun and its absorption by the earth's atmosphere. For his research, he devised various delicate methods and instruments, including his electric compensation pyrheliometer, invented in 1893, and apparatus for obtaining a photographic representation of the infrared spectrum in 1895.