The formation of the solar system

5. formation of the solar system : (8.8 billion year after big bang)

A huge cloud of gas (H,He and other ionised gases) combine with space dust and they form an interstellar cloud known as Nebula.
This giant cloud begin to collapse under its own mass.
Gravity then causes this dust & gase to be continuously dragged into the centre of the cloud,making core very hot and dense.
This form an object called Protostar - which eventually transformed into new star like our sun was formed in this same manner around 4.5 billion year ago.

Around the protostar the collapsing cloud form a rotating disc of material and form a disc called protoplanetary disc new planets are born.
protoplanetary disc is nothing but a huge flat ring comprising hundred of lump of rock and ice called planetesimals.
before our star has born another one had died in supernova filling cloud with gas and dust.this debris gradually form protoplanetary disc :- a huge flat ring comprising hundred of lump of rock and ice called Planetesimals.
this planetesimal is building block of the our solar system.
after a few million year of crashing and melding (mixing together) this planetesimal bodies begin to resemble the planetary embryos or protoplanets.
And finally collision between this protoplanets initiate the final stage and that we called a rocky planet.
Planets that are close to the sun where temperature were too high for volatile chemical,such as water to remain in solid state.
initial protoplanetary disc contained only small amount of rocky solid material so the planet that are close to the sun were comparatively small.
Beyond the Outer edge of asteroid belt where temperature is cool enough for gases to form thick atmosphere around rocky core hence creating gas giant :- jupiter,saturn,uranus,neptune.

Moon formation :

Many moons are former planetesimal captured by planet,but few other infant earth collide with another young planet - huge clump of debris pull out from earth after few million years it meld together to create a moon.
4 billion year ago planets and moon are formed but solar system still different from current one.
probably many more planet than the eight that much be close together over a time outer planet began to move slowly away from sun throwing gravitational force of solar system into out of balance.