Ångström, Anders Jonas (1814-1874)

Swedish astrophysicist who worked in spectroscopy and solar physics. In 1861 he identified the presence of hydrogen in the Sun. His outstanding Recherches sur le spectre solaire (1868) presented an atlas of the solar spectrum with measurements of 1,000 spectral lines expressed in units of one-ten-millionth of a millimetre, the unit which later became the angstrom.

Ångström was educated at Uppsala and spent his entire academic career there. His main work was in spectroscopy, but he also investigated the conduction of heat and devised a method of determining thermal conductivity (1863). His ‘Optical investigations’ (1853) contains his principle of spectrum analysis, demonstrating that a hot gas emits light at the same frequency as it absorbs it when it is cooled. In 1867 he investigated the spectrum of the aurora borealis, the first person to do so.