In 1937 and 1940, Raymond Lyttleton postulated that a companion star to the Sun collided with a passing star. Such a scenario had already been suggested and rejected by Henry Russell in 1935, though it may have been more likely assuming the Sun was born in an open cluster, where stellar collisions are common. Lyttleton showed that terrestrial planets were too small to condense on their own and suggested that one very large proto-planet broke in two because of rotational instability, forming Jupiter and Saturn, with a connecting filament from which the other planets formed. A later model, from 1940 and 1941, involved a triple star system, a binary plus the Sun, in which the binary merged and later split because of rotational instability and escaped from the system, leaving a filament that formed between them to be captured by the Sun. Objections of Lyman Spitzer apply to this model also.