Spitzer, Lyman (1914–1997)

US astrophysicist whose contributions included work on the interstellar medium, which concerns the gas and dust between stars from which new stars form. Early on, Spitzer suggested that the brightest stars in spiral galaxies have formed recently from the gas and dust there. He also noted the presence and importance of interstellar magnetic fields, the likelihood of a multiphase medium – with hot, warm and cool components – and the significance of dust grains.

Spitzer also made major advances in stellar dynamics, contributing to the understanding of ‘relaxation’ and how this process caused a dense stellar system to inexorably approach a singular state, the approach accelerated by the existence of a spectrum of stellar masses but retarded by the presence of binaries.

Spitzer was born in Toledo, Ohio, and studied at Yale. He received his bachelor's degree from Yale in 1935. He spent a year at St John's College, Cambridge University, before earning his PhD at Princeton in 1938. He served on the Yale faculty from 1939 to 1942 before his wartime service at Columbia, then returned briefly to Yale. Later, at Princeton, he was both chair of the Department of Astrophysical Sciences and director of the Princeton Observatory 1947–1979.

In 1946, he proposed the development of large space telescopes that would overcome astronomical ‘seeing’ problems, increase the wavelength coverage available, and function better in the stability of a low-gravity environment. Under Spitzer's direction, a group of Princeton scientists developed the 81-cm/32-in Copernicus ultraviolet satellite, which made several important discoveries after its launch in 1972. He later worked on the development and subsequent refurbishment of the Hubble Space Telescope.

Spitzer proposed that only a magnetic field could contain gases at temperatures as high as 100 million degrees, by which point hydrogen gas fuses to form helium, and he devised a figure-of-eight design to describe this field. His model was important to later attempts to bring about the controlled fusion of hydrogen.

Spitzer criticized the theory that our planetary system is the result of a gas cloud or gaseous filaments breaking off from the Sun to become planetary fragments. He showed that a gas would be dispersed into interstellar space long before it had cooled sufficiently to condense into planets.