Definition
Jan Oort was a Dutch astronomer who revolutionized our understanding of the structure and dynamics of galaxies. The 'Oort cloud' is a vast, spherical region of icy debris far beyond Pluto, thought to be the source of many comets. Think of it as the solar system's distant storage unit. Oort also contributed significantly to understanding galactic rotation and the distribution of mass in galaxies. He figured out how stars move around the center of the Milky Way. His work helped map the unseen universe.