Final answer:
Accretion is the process of slow particle accumulation by gravity and collision, leading to the formation of larger solid bodies like planetesimals, which are essential for planet formation.
Step-by-step explanation:
The process described is known as accretion, which refers to the slow accumulation of solid particles by gravity and collision into larger, solid objects. This is an important mechanism in the formation of celestial bodies, such as planets and stars, from the initial dust and gas in a solar nebula. The process begins with tiny dust particles colliding and sticking together to form larger clumps. As these clumps grow, they can attract more particles due to their increased gravitational influence. However, they must quickly grow to a size larger than about 100 meters in diameter to avoid the effects of drag forces from gas in the disk, which can cause them to lose their orbits and potentially crash into the host star. Eventually, through continued accretion, these bodies can grow to become planetesimals, the building blocks of planets.