SOLAR SYSTEM

Detailed explanation-1: -Over time the planetesimals continued to collide and join together, attracted by gravity. These larger objects, about the size and mass of our Moon, are called protoplanets. The accumulation of material to form planets in this way is called accretion.

Detailed explanation-2: -Planets, including those like our own Earth, form from epic collisions between asteroids and even bigger bodies, called proto-planets. Sometimes the colliding bodies are ground to dust, and sometimes they stick together to ultimately form larger, mature planets.

Detailed explanation-3: -In the solar nebula, dust and ice particles occasionally collided and merged. Through this accretion, these tiny particles formed larger bodies that eventually became planetesimals up to a few kilometers across. In the inner, hotter part of the nebula, planetesimals were composed of silicates and metals.