The First Five Years of Jan Oort at Leiden, 1924 to 1929

Abstract

Gerard P. Kuiper, Pieter Th. Oosterhoff and myself, Bart J. Bok, descended on Leiden University and the Leidse Sterrewacht in late September, 1924. Willem de Sitter was then its Director and Ejnar Hertzsprung his chief associate. Jan Oort had recently been appointed a conservator (senior scientist) at Leiden. Oosterhoff had planned to study celestial mechanics under De Sitter and Jan Woltjer, but he was promptly taken in hand by Hertzsprung, who booked him permanently for work on variable stars. Kuiper turned to Hertzsprung and planned his own work on binary stars, the field of his ultimate doctoral thesis. During my high-school years in the Hague, I had developed an interest in our Milky May system, inspired by the controversies of the early 1920’s, which involved Harlow Shapley (whom I admired) and Heber D. Curtis - controversies in which Kapteyn and Easton figured prominently. Kapteyn had died two years before I arrived at Leiden. Small wonder that right at the start I turned to Jan Oort as my mentor. Jan and I share the same birthday, 28 April, but Jan is precisely six years ahead of me - a fact he never permits me to forget! Jan had come to Leiden as the former student of J.C. Kapteyn and Piet van Rhijn. To the new arrival Bart Bok, he was the man who had learned his trade from one of the great names of the recent past and from the man who had inherited Kapteyn’s throne. It was a great thing to have come to Leiden, direct from a city high-school in the Hague.