Complex sentence: Jacobus Cornelius Kapteyn, (January 19,1851, Barneveld, Gelderland--June 18,1922) was a Dutch astronomer, best known for his extensive studies of the Milky Way and as the first discoverer of evidence for galactic rotation.
Split into simpler sentences: Jacobus Cornelius Kapteyn, (January 19,1851, Barneveld, Gelderland--June 18,1922) was a Dutch astronomer. He carried out extensive studies of the Milky Way and was the discoverer of evidence for galactic rotation.