Schwarzschild, Martin (1912–1997)

German-born US astronomer whose most important work was in the field of stellar structure and evolution. He greatly narrowed the estimated range of mass that stars can have.

Schwarzschild was born in Potsdam, the son of astronomer Karl Schwarzschild. After studying at Göttingen, he emigrated to the USA in 1935. He was professor at Columbia 1947–51 and at Princeton from 1951.

Schwarzschild worked out a quantity (ZHe) for the total mass density of the elements heavier than helium, using the density of hydrogen as one unit. The values of ZHe are smallest for old stars (0.003) and largest for young stars (0.04), implying that the most recently formed stellar objects were formed out of a medium of interstellar gas and dust that was already enriched with heavy elements. These elements were probably produced in stellar interiors and expelled by the oldest stars.

In 1938, Schwarzschild suggested that the star's deepest interior pulsates, but that in the outermost regions the elements of gas do not all vibrate in unison, causing a lag in the light curve by the observed amount. In 1959, he obtained structural details of the surface of the Sun and photographs of sunspot penumbrae by using a balloon-supported solar telescope at 24,385 m/80,032 ft.

Schwarzschild died in 1997.