How were planetesimals formed?

Planetesimals formed through the process of accretion in the early solar system, when dust and ice particles in the protoplanetary disk began to stick together due to electrostatic forces and later gravitational attraction. Over time, these small aggregates collided and merged, gradually growing larger as they accrued more material. As planetesimals reached sizes of about a kilometer or more, their gravity became strong enough to attract additional matter, leading to the formation of protoplanets. This process ultimately contributed to the development of planets in our solar system.