SOLAR SYSTEM

Detailed explanation-1: -Dust clumps become pebbles, pebbles become larger rocks that grind together to expand. The presence of gas helps particles of solid material stick together. Some break apart, but others hold on. These are the building blocks of planets, sometimes called “planetesimals."

Detailed explanation-2: -Planetesimals are the building blocks of planets. Asteroids and comets are leftover planetesimals from the time of formation of our own solar system. The formation of km-sized or larger planetesimals remains an open problem in planet formation theories.

Detailed explanation-3: -Accretion theory explains how cosmic dust was drawn together to form planetesimals by gravitational forces. These planetesimals would form protoplanets which would accumulate more matter to build the planets in the solar system.

Detailed explanation-4: -Within the solar nebula, scientists believe that dust and ice particles embedded in the gas moved, occasionally colliding and clumping together. Through this process, called “accretion, ‘’ these microscopic particles formed larger bodies that eventually became planetesimals with sizes up to a few kilometers across.

Detailed explanation-5: -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.