Astronomy Bio...Martin Schwarzschild
Martin Schwarzschild is an American astronomer born in Potsdam, Germany, on May 31,1912, the son of the astronomer and mathematician, Karl Schwarzschild. In 1935, Martin Schwarzschild received his PhD in astronomy from the University of Gottingen. He then immigrated to the United States and eventually became a naturalized American citizen. In 1937 he was a Nansen Fellow at the University of Oslo and from 1937 to 1940 he was a Littauer Fellow at Harvard University. In 1940 he was a Lecturer in Astronomy at Columbia University, in 1944 he became an assistant professor and in 1947 a professor. In 1951 Schwarzschild obtained the position of Huggins Professor of Astronomy at Princeton University. He is a member of the National Academy of Sciences and from 1970 to 1972 he was the President of the American Astronomical Society
Schwarzschild's primarily research involved the theory of stellar structure and evolution. He has contributed many articles on the internal constitution of stars and made astronomical observations using telescopes carried by balloons into the stratosphere. In 1959 he compiled structural details using photographs of the Sun's surface and sunspot penumbrae by using a balloon-supported solar telescope at 24,385 meters.
Arthur Eddington was interested in the fact that whereas stars differ greatly in brightness, density and in some physical properties, they differ relatively little in mass. By 1926 the range of known stellar masses ran from 1/6 to 100 times that of the Sun. Since 1926 the upper limit has been reduced and much of the work on assessing these limits was done by Schwarzschild. It is now thought that the upper limit is only 65 solar masses. The smallest stellar masses known are about 1/100 that of the Sun or about 10 times the mass of Jupiter.
Schwarzschild also worked out a quantity (ZHe) for the total mass density of elements that are heavier than helium, using the density of hydrogen as one unit. The values of (ZHe) are smallest for older stars (0.003) and largest for young stars (0.04), implying that the most recently formed stellar objects were formed from 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.
Schwarzschild has also been involved with what is known as pulsation theory. In 1879, even before variations in radial velocities was known, Arthur Ritter had considered the periodic expansions and contractions of a star, which are termed "radial pulsations". In 1938 Schwarzschild suggested that the star's deepest interior pulsate, 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.
Throughout his distinguished career, Schwarzschild has made an enormous contribution to our understanding of the dynamics and structure of stellar objects.