Jacobus Kapteyn
JAN 19, 2016
DOI: 10.1063/PT.5.031136
On this date in 1851 Jacobus Kapteyn, who discovered the first evidence of galactic rotation, was born in Barneveld, Netherlands. After earning his degree from the University of Utrecht, he worked at the Leiden Observatory then was appointed the first Professor of Astronomy and Theoretical Mechanics at the University of Groningen. In 1904, while studying the proper motion of stars, he determined that stars could be divided into two streams, moving in nearly opposite directions. Although it was not realized at the time, this was the first evidence that the Milky Way was rotating. (Paintings by Jan Pieter Veth)
Date in History: 19 January 1851
© 2016 American Institute of Physics
