What is the role of accretion disks in the formation of the solar system?

The role of accretion disks in the formation of the solar system is a critical one. Accretion disks are rotating disks of gas and dust that surround young stars, including the protosun, which eventually form planets. The formation of planets from accretion disks is a multi-step process, involving the gravitational attraction and collision of small particles, which clump together to form larger objects, which then collide and coalesce into planetesimals, and eventually planets. Accretion disks are the source of the material that forms these planetesimals and planets.

The initial stage of the process involves the growth of dust grains in the protoplanetary disk through the sticking together of tiny grains by van der Waals forces. As the grains grow larger, the force of gravity begins to play a role in their evolution, leading to the formation of larger planetesimals.

The material in the accretion disk is distributed non-uniformly, with the majority of the mass concentrated in the central region, closer to the star. This concentration of mass leads to the formation of density waves, which can cause particles to collide and stick together, leading to further growth.

As the planetesimals grow larger, their gravitational pull increases, allowing them to attract smaller objects in their vicinity. The final stage of planetary formation involves the collision and merging of planetesimals to form planets.