YouTube Edgar here and Welcome to artifexian. Here you will learn everything you ever wanted to know about world building and then some.
so this particular story starts
4.6 billion years ago when gravity caused a giant molecular cloud to collapse and begin forming our sun
The cloud that spawned our sun is thought to have measured 65 light years across as it collapsed it
fragmented into several one parsec wide regions and inside each of these regions a star began to form
Scientists believe that our sun formed within the cluster of several thousand other stars
Now when this giant cloud collapsed it had a little bit of angular momentum
So not all the matter collapsed into the central star forming region
Material also began to orbit around the protosun forming a protoplanetary disk
Roughly 200 au in diameter it is in this disk that the planets as we know them began to form
The disk was composed of gas and dust
Now when I say dust I don't mean dust in the household sense rather
Cosmic dust is comprised of tiny rock particles less than a Micron in size
These grains began to stick together and grew in size until they formed one kilometer wide objects known as planetesimals
These one kilometer planetesimals were massive enough to begin
Gravitationally attracting each other and as a result they continued to grow in size through a process known as accretion
Once massive enough gravity caused Runaway creation to occur which sped up the growing process of the planetesimals
It's thought that the inner solar system at this point contained 50 to 100 moon to mars size objects known as planetary Embryos
Now for reasons unknown to science the planetary disc is thought to have lost much of its gas at this point
Which caused the orbits of these planetary embryos to become unstable.
This instability led some of these protoplanets to collide forming the planets as we know them today
Such collisions are thought to have formed the moon and remove Mercury's atmosphere
Close in to our sun
Rocky Planets formed because the temperatures were high enough to allow for the accretion of high boiling point materials like iron, nickel
and aluminium
The rarity of these heavy elements place an upper limit on how big rocky planets could grow.
The gas giants formed out beyond what is known as the frost line.
Here it was cold enough for volatile icy compounds to be solid.
The gas giants are thpught to have rocky cores of Roughly 5 to 10 Earth masses.
This critical level caused a process called hydrostatic flow to occur,
Sucking in all the hydrogen and helium gas and sticking into the core forming a thick gaseous atmosphere or envelope
When the protosun had gained enough mass to begin nuclear fusion in its core it sent a shock wave through the planetary disc,
Essentially clearing out all the excess material in the disk and for the most part
ending Planet formation.
Any materials left over after solar winds tore through our system became the asteroid belt, Kuiper belt and Oort Cloud
Interestingly though uranus and neptune are thought to have formed after the solar wind
Because they contain much less hydrogen and helium than jupiter or Saturn
Planetary migration is a poorly understood yet essential part of how our solar system came to be
Simply put it is believed that neptune and uranus formed much closer in to our sun
And then migrated outwards once the inner solar systems planets tended to migrate inwards.
Eventually slotting into the nice orderly configuration we call our solar system.
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