Anders Jonas Ångström (pronounced /ˈæŋstrəm/; Swedish: [ˈânːdɛʂ ˈjûːnas ˈɔ̂ŋːstrœm]; August 13, 1814 – June 21, 1874) was a Swedish scientist who helped create the field of spectroscopy, which studies how light interacts with matter.

Ångström is also known for his research on astrophysics, how heat moves, Earth's magnetic field, and the northern lights. In 1852, he wrote a book called Optiska undersökningar (Optical investigations), where he described a rule about how light is absorbed. This rule was later adjusted and became known as Kirchhoff's law of thermal radiation.

Biography

Anders Jonas Ångström was born in Medelpad to Johan Ångström and received his early education in Härnösand. In 1833, he moved to Uppsala and studied at Uppsala University, where he became a lecturer in physics in 1839. In 1842, he worked at the Stockholm Observatory to learn practical astronomy, and in 1843, he was named keeper of the Uppsala Astronomical Observatory.

He was interested in studying changes in Earth's magnetic field and collected data on magnetic intensity across Sweden. The Stockholm Academy of Sciences assigned him the task of analyzing magnetic data from the ship HSwMS Eugenie during its global voyage from 1851 to 1853. This work was not completed until near the end of his life.

In 1858, he took over the physics chair at Uppsala from Adolph Ferdinand Svanberg. His most important research focused on heat transfer and spectroscopy. In his 1853 work, Optiska Undersökningar, presented to the Royal Swedish Academy of Sciences, he explained that electric sparks produce two overlapping spectra: one from the metal in the electrode and another from the gas around it. He also used Leonhard Euler’s theory of resonance to conclude that glowing gas emits light with the same wavelength as it absorbs. This idea, noted by Sir Edward Sabine when awarding him the Rumford Medal in 1872, became a key principle in spectroscopy.

From 1861 onward, he studied the solar spectrum. By combining spectroscopy with photography, he proved that the Sun’s atmosphere contains hydrogen and other elements in 1862. In 1868, he published a detailed map of the solar spectrum in Recherches sur le spectre solaire, including measurements of over 1,000 spectral lines. These measurements were widely used but slightly inaccurate due to an imprecise standard meter.

In 1867, he studied the aurora borealis and identified a bright yellow-green line in its spectrum. However, he incorrectly believed this line also appeared in the zodiacal light.

He was elected to several learned societies, including the Royal Swedish Academy of Sciences in 1850, the Royal Society in 1870, and the Institut de France in 1873. He died in Uppsala on June 21, 1874.

In 1845, Ångström married Augusta Bedoire (1820–1906), daughter of Jean Henric Bedoire and Catharina Henrietta Littorin. The Bedoire family was a Stockholm merchant family of Huguenot origin.

His son, Knut (1857–1910), also became a physicist.

Honors

The Ångström unit (1 Å = 10 m), which is sometimes used to measure the wavelengths of light and the spaces between atoms in solid materials, is named after him. This unit is also used in crystallography and spectroscopy.

A crater on the Moon, called Ångström, is named in his honor.

One of the main buildings at Uppsala University, the Ångström Laboratory, is named in his honor. This building includes several departments, such as the Department of Physics and Astronomy, the Department of Mathematics, the Department of Engineering Sciences, the Institute of Space Physics, and the Department of Chemistry.