SOLAR SYSTEM

Detailed explanation-1: -shockwave, that can create the smallest little sections of the nebula to contract. the extra little squeezing of the gas can be enough to start the process.

Detailed explanation-2: -Answer. As gravity causes the cloud to contract, the particles of gas and dust move faster and collide often. These collisions generate heat and light. At the same time, the pressure and temperature of the cloud increases.

Detailed explanation-3: -The young solar nebula begins to collapse because of gravity. As the solar nebula rotates, it flattens and becomes warmer near its center. Planetesimals begin to form within the swirling disk. Four other protoplanets became Jupiter, Saturn, Uranus, and Neptune.

Detailed explanation-4: -I. Contraction of insterstellar cloud. Solar system formed about 4.6 billion year ago, when gravity pulled together low-density cloud of interstellar gas and dust (called a nebula)(movie).