Complex sentence: Jan Hendrik Oort ForMemRS (28 April 1900--5 November 1992) was a Dutch astronomerwho made significant contributions to the understanding of the Milky Wayand and pioneer in the field of radio astronomy.
Split into simpler sentences: Jan Hendrik Oort ForMemRS (28 April 1900--5 November 1992) was a prolific Dutch astronomer. He made many important contributions in the field of astronomy and was a pioneer in the field of radio astronomy.