There are four major theories that are still considered as plausible for the formation of the solar system.
1. Proto-planet Theory: McCrea, in 1960, gave a monistic theory trying to explain simultaneously the formation of Sun and the planets. He started with a cloud of dust and gas in a state of hypersonic turbulence. Thus, rapid internal collisions took place. This resulted in aggregation of masses at various places. He experimented with parameters like mass and radius of cloud to explain the current state of the solar system. He gave a revised theory in 1988.
2. Capture Theory: The theory, given by Woolfson in 1964, considers an interaction between a condensed solar mass star (SUN) and a protostar of lesser mass. The protostar entered the Roche limit and was disintegrated to form bodies like planets. This would give a planar structure but highly elliptical orbits.
3. The Solar Nebula Theory: This theory, given by Cameron in 1973, begins with a slowly rotating nebula very similar to the Laplacian theory. The planet formation starts with a disc of 0.01 to 0.1 solar masses. This is also a monistic theory dealing with mass and angular momentum distribution.
4. The Modern Laplacian Theory: This theory is also derived from the Laplacian theory and was given by Prentice in 1974. He started with a cool gas cloud which condensed in such a way that the angular momentum of the central body was only 1 percent of the system. His contribution was mainly giving a mathematical explanation of the process of formation. The theory also explains formation of planets in concentric rings.