German physicist · 1824–1887
Gustav Kirchhoff
Gustav Kirchhoff turned flame colours into a science. With Robert Bunsen he founded spectroscopy and discovered caesium and rubidium, and he explained what the dark lines in sunlight reveal about the Sun.
- Elements credited
- 2
- Discoveries
- 1860–1861
- Co-discoverers
- 1
- Where
- Germany
The work
Kirchhoff supplied the physics behind the spectroscope he and Bunsen built in Heidelberg. He established that each element gives a unique set of bright lines when hot and absorbs the same wavelengths when cool light passes through it.
That insight let the pair identify caesium and rubidium from lines no known element produced, and let Kirchhoff show that the dark Fraunhofer lines in sunlight come from sodium, iron and other elements in the Sun’s atmosphere. For the first time, scientists could tell what a star was made of.
Caesium and Rubidium side by side
Life and career
Kirchhoff was born in Königsberg, Prussia. While still a student in 1845 he formulated his laws for currents and voltages in electrical circuits, which are taught to every engineering student today.
He worked with Bunsen in Heidelberg and later moved to Berlin as professor of theoretical physics. His study of how hot objects emit light, black-body radiation, set the problem that Max Planck solved by inventing quantum theory.
Also known for
- Kirchhoff’s circuit laws
- Kirchhoff’s laws of thermal radiation
- Coined the term black body