Jacobus Kapteyn
Jacobus Cornelius Kapteyn was a Dutch astronomer. He carried out extensive studies of the Milky Way and was the discoverer of evidence for galactic rotation.
Kapteyn was born in Barneveld to Gerrit J. and Elisabeth C. Kapteyn, and went to the University of Utrecht to study mathematics and physics in 1868. In 1875, after having finished his thesis, he worked for three years at the Leiden Observatory, before becoming the first Professor of Astronomy and Theoretical Mechanics at the University of Groningen, where he remained until his retirement in 1921. In 1888 he became a member of the Royal Netherlands Academy of Arts and Sciences.
Source: Wikipedia