Lodewijk Woltjer (born 1930) studied at the University of Leiden under Jan Oort earning a PhD in astronomy in 1957 with a thesis on the Crab Nebula. This was followed by post-doctoral research appointments to various American universities and the subsequent appointment of professor of theoretical astrophysics and plasma physics in the University of Leiden. From 1964 to 1974 he was Rutherford Professor of Astronomy and Chair of the Astronomy Department at Columbia University in New York.