Dutch astronomer Jacobus Kapteyn was born #OTD in 1851.
Kapteyn spent much of his life counting stars and measuring their magnitudes and proper motions, with a goal of determining the shape and size of the Galaxy. He concluded after decades of work that the Galaxy was about 30,000 light-years across and perhaps 10,000 light-years thick, with the Sun not too far from the center. His model of the universe came to be called the Kapteyn universe. via @LindaHall_org
