news and views Obituary numerical algorithms and even new Mar tin Schwarzschild (1912–97) methods of computation. As a result, Schwarzschild worked with John von Astrophysicist instrumental in Neumann in the 1940s at Princeton to develop the first digital electronic developing the modern computers used for scientific research. theory of stars and galaxies A second example is taken from the dynamics of galaxies, to which field Astrophysics, as a theoretical discipline Schwarzschild returned after his formal designed to provide an understanding of retirement in 1979. He had realized that the observable Universe, was born, came the usual assumption concerning the of age and flourished in the twentieth symmetry of galaxies — that they are century. Although it is perhaps the oldest essentially symmetrical around an axis of quantitative science, before 1900 it rotation — was just that: an untested was almost exclusively assumption. He then began a series of concerned with the positions studies to examine the issue and motions of planets and observationally and to see whether self- stars. For dynamical purposes, consistent models could be constructed planets and stars could be that would deviate from this assumption, treated as point objects. Only in the yet agree with observations. The work twentieth century did we begin seriously again involved massive numerical to inquire into the interior structure, computations, and it revolutionized our origin and evolution of these ‘points’. despite a few remaining puzzles (the understanding of ‘elliptical’ galaxies. They Martin Schwarzschild, who died on 10 nature of type-II supernovae, and the low are now known to be triaxial systems in April, was at the centre of this scientific level of neutrino emission from the Sun, general, for which rotation is not the transformation. He was born and educated for example), there is an extraordinarily principal dynamical force. in pre-war Germany, arriving in the United good match between theoretical models of Schwarzschild’s capacity to strip all States (via Norway) in 1937. After a decade stars — singly, in pairs and in clusters — problems to their essential elements, of military service and junior positions at and the bulk of the astronomical evidence. combined with his vivacious personality, Harvard and Columbia, he moved to Schwarzschild’s style as a scientist produced one of the great teachers and Princeton as a professor. There he joined combined traits rarely found together in a expositors of his discipline. He was equally Lyman Spitzer Jr, the two of them single person: a broad and imaginative famous for large public lectures and for his establishing Princeton University creativity based on a thorough intimate ties to and guidance of his Observatory as a centre of excellence in understanding of physical principles; a students. A person of enormous modesty theoretical astrophysics, often working passion for detailed and precise numerical and charm, he was as well loved by peers together, until they both died within weeks work to determine the consequences of and colleagues as by students and others in of each other almost exactly half a century physical models; and an enormous respect all occupations whom he met in daily life. from their initial appointments in the for observations — the facts of nature as The recipient of essentially every major spring of 1947. the ultimate arbiters of truth. honour available to a theoretical Nature and nurture conspired to A few examples make these points astrophysicist, he was awarded the US provide an ideal environment for vividly. Most early work on stellar National Medal of Science, unfortunately Schwarzschild. His uncle, Robert Emden (a structure had treated stars as being of posthumously on 30 April 1997, with the professor of physics and meteorology), uniform composition. Schwarzschild citation: “For his seminal contributions to published the famous book Gaskugeln realized that, through the expected the theory of the evolution of stars, and his (Gas Spheres) in 1907, establishing the processes of nuclear burning, stars would creative insights into galactic dynamics treatment of stars as gaseous bodies within develop discontinuities in chemical which form the basis of much of the which the forces of Newton’s gravity and composition, smoothed out only by contemporary astrophysics; and his gas pressure are in equilibrium. His father, relatively inefficient diffusion. In a series lifetime of dedication to students. His Karl Schwarzschild, was the author of the of papers with many associates (including influence on US astronomy in the second famous Schwarzschild (spherical) solution Alan Sandage and Fred Hoyle) that began half of this century is unsurpassed.” A to Einstein’s equations. Martin became in the late 1940s and continued through thoroughly cosmopolitan scientist, he was probably the leading developer of the the early 1970s, he showed that these as honoured in the United Kingdom as in theory of stellar evolution. discontinuities have powerful effects on the United States. He won the gold medal Largely because of his contributions to stellar structure, producing surprising of the Royal Astronomical Society in 1969 this field, we can now follow the progress internal effects such as burning in unstable and was elected a foreign member of the of a typical star after it contracts out of the shells, or externally observed effects such Royal Society in 1996. interstellar medium and begins to burn its as extended red-giant envelopes. It seems unlikely that history will nuclear fuel through a sequence of phases: Approximate analytic theory, or provide another such moment, when one main sequence (like the Sun) to red giant perturbation theory applied to existing individual can have such a large effect on (like Antares) to degenerate dwarf (like exact analytic solutions, could not begin to our view of the essential elements of the Sirius B). By now there are innumerable address this problem even qualitatively, Universe. quantitative tests of the theory of stellar because the equations of stellar structure Jeremiah P. Ostriker evolution. And it works! One must are highly nonlinear and have two Jeremiah P. Ostriker is at the Office of the Provost, consider it the greatest triumph of boundary conditions, at the centre and the 3 Nassau Hall, Princeton University, Princeton, astrophysical theory in this century that surface. So it was necessary to develop new New Jersey 08544, USA. NATURE VOL 388 31 JULY 1997 430 Nature © Macmillan Publishers Ltd 1997 | |.