Jacobus Kapteyn. Portrait of Jacobus Cornelius Kapteyn (1851-1922), Dutch astronomer. He published a catalogue in 1900 which took 12 years to produce and which contained the positions of 455,000 southern hemisphere stars. He also investigated the stars' motions and discovered in 1904 that they moved in preferred directions. This star streaming was later found to be due to the differential rotation of our galaxy around a distant point. He devised a cosmological model in which the universe had an ellipsoid shape (axes ratio of 5:1), flattened in the plane of our galaxy.