Astronomy in the Time of Pannekoek and Pannekoek as an Astronomer of his Times

The astronomical enterprise underwent enormous changes during Pannekoek’s lifetime, including, most importantly, in terms of the technical content and practices of the science, the rise of astrophysics. I suggest that the history of astrophysics between the 1860s and early 1950s can be divided roughly into three stages and that in his later career Pannekoek is best seen as a ‘third-stage’ astrophysicist. The institutional landscape of astronomy was also transformed during Pannekoek’s lifetime, most tellingly with the emergence of the United States as the leading nation for observational astrophysics. However, in the Netherlands, J.C. Kapteyn had shown that it was possible to be an active astronomer without a telescope and Pannekoek would do the same, and fashioned a successful career as an interpretive and theoretical astrophysicist.