ANGSTROM, ANDERS JONAS Swedish physicist, was born on Aug. 13, 1814, at Logdo, Medelpad, Sweden. He was educated at Uppsala university, where in 1839 he became Privatdozent in physics. In 1843 he became observer at Uppsala Observatory. In 1858 he succeeded Adolph Ferdinand Svanberg (1806-1857) in the chair of physics at Uppsala, and there he died on June 21, 1874. His most important work was concerned with the conduction of heat and with spectroscopy. In his optical research Optiska Undersokningar, presented to the Stockholm Academy in 1853, he not only pointed out that the electric spark yields two superposed spectra, one from the metal of the electrode and the other from the gas in which it passes, but deduced from Euler's theory of resonance that an incandescent gas emits lumi nous rays of the same refrangibility as those which it can absorb. This statement entitles him to rank as one of the founders of spectroscopy. The Angstrom unit was named in his honour.
From 1861 onwards he paid special attention to the solar spec trum. He announced in 1862 the existence of hydrogen, among other elements, in the sun's atmosphere, and in 1868 published his great map of the normal solar spectrum, which long remained authoritative in questions of wave-length although his measure ments were inexact to the extent of one part in 7,000 or 8,000, the metre which he used as his standard having been slightly too short. He was the first, in 1867, to examine the spectrum of the aurora borealis and to detect and measure the characteristic bright line in its yellow green region; but he was mistaken in supposing that this same line, which is often called by his name. is also to be seen in the zodiacal light.
His son KNUT JOHAN ANGSTROM (1857-191o) became pro fessor of physics at Uppsala in 1896. He investigated the radia tion of heat from the sun and its absorption by the earth's atmos phere and devised various delicate methods and instruments, including his electric compensation pyrheliometer, invented in 1893, and apparatus for obtaining a photographic representation of the infra-red spectrum (1895).