Portrait of the British astrophysicist and mathematician Sir James Hopwood Jeans, 1877-1946. Jeans proposed the 'tidal' or 'passing star' theory for the formation of the solar system, whereby the gravitational pull of a star passing close to the sun extracted a filament of material from which the planets subsequently condensed. This theory was later abandonned for a modified version of the nebular theory of Laplace (1749- 1827), that the sun and the planets were formed from a rotating disc of gas.