(1814-1874) Swedish Spectroscopist, Astronomer
Anders Angstrom is known as the father of spectroscopy, the branch of physics that studies light by using a prism or diffraction grating to spread out the light into its range of individual colors or spectrum.
Angstrom was born in Logdo, Sweden, on August 13, 1814, the son of a chaplain. He attended the University of Uppsala, where he obtained his doctorate in physics in 1839. That same year, he became a lecturer at the university and, four years later, an observer at the Uppsala Observatory. His first significant research project involved the development of a method of measuring heat conductivity, which enabled him to demonstrate that it was proportional to electrical conductivity.
He published Optical Investigations, his most important work, in 1853; in it he presented his principle of spectral analysis. He had studied electric arcs and discovered that they yield two spectra, one superimposed on the other. The first was emitted from the metal of the electrode itself, the second from the gas through which the spark passed. He was also able to demonstrate that a hot gas emits light at the same frequency as it absorbs it when it is cooled. Angstrom had established his reputation and was elected to the chair of physics at the University of Uppsala in 1958.
Angstrom’s early work provided the basis for the spectrum analysis that would occupy him for the rest of his life. In 1862 he announced his hypothesis—which would later be confirmed—that the Sun’s atmosphere contains hydrogen. The solar spectrum was his primary interest, but in 1867 he also became the first person to study the spectrum of the aurora borealis, the spectacular display of blue, pink, red, orange, and yellow light seen in the night sky in the Northern Hemisphere during the fall and winter. He used a spectroscope consisting of a simple triangular prism, which broke up the white light passing through it into a rainbowlike band of colors known as a spectrum. Looking through this prism with the aid of a telescope, he showed that the light of the aurora borealis differed from that of the Sun. He thus reached the momentous conclusion that no two substances have the same spectrum and, therefore, that any substance can be identified by its spectrum.
In 1868 he published his famous Researches on the Solar Spectrum, which contained measurements of the wavelengths of more than 1,000 lines in the Sun’s spectrum, known as Fraunhoferlines, measured to six significant figures in units of 100 millionths of a centimeter (10-8 cm).
Another of his important achievements was his atlas of the normal solar spectrum, published in 1869, which became a standard reference tool. He remained at the University of Uppsala until his death on June 21, 1874.
Angstrom’s legacy is visible in the work of contemporary astronomers and astrophysicists, who still identify elements found in stars through the use of spectroscopy.
The unit of measure for the wavelength of light, officially adopted in 1907, is called the angstrom in his honor. Signified by A and equal to one hundred millionth of a centimeter (10 -8 cm), the angstrom serves as a convenient unit that can be used to specify radiation wavelengths, which enables physicists to avoid writing large numbers of zeroes, when discussing the wavelength of light.
