Bertil Lindblad (1895-1965), Swedish astronomer and proposer of the theory of galactic rotation. In 1926, after studying Kapteyn's work on the movements of groups of stars, he postulated that the Sun was revolving around the centre of the galaxy, which was later confirmed by Jan Oort. The Sun is now known to be orbiting the galactic centre at around 22 kilometres per second. Lindblad also worked on the dynamics of spiral galaxies, suggesting methods by which their spiral nature could form and be maintained.