physicist and astrophysicist who developed a theory of expansion and compression of gas spheres and applied it to stellar structure.

In 1889 Emden was appointed to the Technical University of Munich, where he became professor of physics and meteorology in 1907. His famous book Gaskugeln (1907; “Gas Spheres”) was a very important early work on the theory of stellar structure; it develops the physical theory of a gas sphere acted upon by its own gravity. He also devised a hypothesis, no longer taken seriously, to explain sunspots.

In 1924 Emden became honorary professor of astrophysics at the University of Munich, where he remained until his retirement in 1934. He took a leading role in founding the Zeitschrift für Astrophysik (“Journal of Astrophysics”) in 1930 and edited it for six years.