SOLAR SYSTEM

Detailed explanation-1: -The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas. As these clumps get bigger and bigger, their gravity gets stronger and stronger. Eventually, the clump of dust and gas gets so big that it collapses from its own gravity.

Detailed explanation-2: -Intergalactic space is filled with clouds of gas (mostly H + He) and dust known as molecular clouds. These clouds are supported against gravitational collapse by their thermal pressure, but if the clouds get too big massive, gravity wins and they can start to collapse.

Detailed explanation-3: -As enormous clouds of cool gas collapse under the force of gravity, matter is compressed into swirling clouds that force particles to collide at a faster and faster rate, generating heat.