As captured planets would have initially eccentric orbits, Dormand and Woolfson proposed the possibility of a collision. They hypothesized that a filament was thrown out by a passing protostar and was captured by the Sun, resulting in the formation of planets. In this idea, there were 6 original planets, corresponding to 6 point-masses in the filament, with planets A and B, the two innermost, colliding. A, at twice the mass of Neptune, was ejected out of the Solar System, while B, estimated to be one-third the mass of Uranus, shattered to form Earth, Venus, possibly Mercury, the asteroid belt, and Oort Cloud.