This guide Was impossible To Create Without These Cool Guys and Stuffs :
(1) Improved Orion Nebula Model ( Link is not Available on Creating period of guide ) :(


(2) Realistic Nebula Models More Random Nebulas Models Created by Leyo

Thanks a lot to all these Guys.

Some other Guides That can have Relation to this guide :

https://cs2bus.com/sharedfiles/filedetails/?id=3306139352
https://cs2bus.com/sharedfiles/filedetails/?id=3328386561
https://cs2bus.com/sharedfiles/filedetails/?id=3081840420

Star Forms in Nebulous molecular Clouds by helping gravity and Nuclear Fusion.
They Take Millions of Years in this process.

As we said They Build from a dense Molecular region of a nebula, Actually it has Very low density Area Where the Star births. In fact If you create an earth sized nebula It'll weigh only few Kilograms.
they are less dense than any Vacuum created on earth.

We are Going to take a Nebula and a Hypothetical Star as well as its planets, All will be Created in same Nebula. We will Explain Its main phases during its infancy and before Birth. There will be some Chapters which will Define Changes during Hundreds of thousands years.

Let's Say our Star Can Born in about 10 Million Years.

First of all Let's See Where Our Star will birth, Look at this Image, Its Orion Nebula and this is Closest Star Forming Region, This nebula Contains approx 180 Star Forming Regions, For instance We take One of them.




In this image You see I have placed mark around some places These are the Regions Where stars forms But You Won't Be able to look those stars until their Shine Reaches to Enough Magnitude That's Why You can't see any star Being Form in such areas. Actually They are Either still Collecting Particles or just started to attract Each other. For Better Understanding You can Check in SpaceEngine and go inside of a nebula and you will see nothing. Obsivously You can't See Sub-atomic Particles on your vision.

We are inside of a nebula and we're gonna See a star which is about to birth, rather than star you will see Fog and Interstellar Dust and Gas.


Let's Look our Area in Subatomic level, We see the Gas Particles are Constantly Moving in Every Directions Without any Obstacle They are Free to wherever want to go nobody will Stop them. Some are Colliding with each other and change their Trajectory.




You see them for several Hundreds Years and nothing happens, they are just Flying and Colliding each others There is Not anything like attraction or gravity. They will probably stay forever in this phase Our star Will never Birth If they are Constantly Going To and Fro That is our main Problem.

If you have a Curious Mind Probably thinking There is Billions to Trillions of Nebulae in universe, If you asked to me that If a nebula can make Hundreds of stars then Why The Nebulae still present in space Because They are Very old maybe Older than Stars, Just Think Not Every Nebulae has Stellar nursery, Some of them are Stellar Remnant, Many are Planetary Nebulae which form when a Red Giant Star Loses its Outer Shell and So on. That's Why Every Nebulae Don't Create Stars and Even they are creating We can't see their Particle interactions Unless We have Proper Equipment. So Don't say Star will form from any Nebula. They have Special Condition For this.

If you wanna know what can be the Reason For Birth of a star, Just Keep Reading This guide.

As We know Inside a gas, Subatomic particles Don't Attract by themselves But They Need a Trigger to Getting Closer toward them. So Even They are Constantly wandering inside Gaseous Medium, Colliding Too, Nevertheless They Wont attract automatically. When The Flash or Shockwave of Supernovae or Jets of black hole Go Through This Medium The Photons of Radiation Ionise these Particles and they change their behaviour. When Shockwave of a supernova Travel inside a nebula or such a star forming region, The Gas clouds Gets Compressed Because Their Movement Field Become Shorter and they oblige to Move in more dense area than before.

Here are some Triggers for Star Formation :

(1) Super massive Black holes

(2) Supernovae

(3) Still Unknown

by helping Those Agents Nebula's Gaseous clouds compresses and the Particles Come close to each other. When They come enough close they join and become more hot energetic, massive and charged their mutual gravity Increases as well.

Suppose ! Our Star Forming Region has Experienced a Supernova Shockwave and it Became Compressed Like We Changed The Size of Swimming pool or Gas Container. As their Free Roaming Place Gets Shorter They Feel More pull Toward each other.



In this image, Our Star forming area's Particles are in a compressed region and they are feeling much more pull.




After That they come close to each other and when they Merge Their Energy will combine, as a result They will Attract More particles.



At a certain point They have gained mass, Heat and pressure enough to Stick their Nuclei with others. Finally First But Very Tiny (in Infrared) Glow Comes From There and they Continue this process. After Some thousands years They Will become Much larger.

2 Millions years ago, a supernova's Shockwave Disturbed our Star Forming Zone and It became a large Fog Like Structure.





Our Fog is still gathering Gases and Particle's Energy is strong enough to generate a Very Dim Light



In this image You can see our Gas's Mist. Let them Gather more Gases and Temperature and pressure.

In almost 5 Millions Years, Our Gas cloud has Completely changed its appearance. it can Glow by its own Light But If you look our Region You'll Say Its a still part of a nebula.




This is Early Stage of our Protostar. This is still Gathering Gas and dust.

We are watching Our Star past 9 Million Years but Now We see a More Bright Light is coming from our Star Forming Region. Our star is about to Enter in its Protostar phase.



a View from Far Side

After 10 Million years, Our Little Star is Ready to Govern her System But still she is Forming and has to Make Herself Complete. Our Star Forming Region has completely Changed during This Process,
Now This Zone will called a Proplyd (ionized Proto-planetary Disk) . Our Star has Almost Gained Enough mass and Features like a Main Sequence Star But Still She is not completed, Our
Stellar Forming Region has still some Gas and dust Which has not used as a Food To our Baby Star.
So Rest of the material Will Orbit our Baby Star or Protostar Due to its immense Gravity.




If you look at our Forming Region from far side it'll look like a Dark knot or Diamond or Just a point



There she is, Inside the shell of Dense Cloud, Our baby star is still gathering Gas and Dust. it is Ejecting High Velocity Jets from its poles.

Our Protostar has some New Structures, Lets know about them.


Protostar

It is our baby star Which has Born after Long Lasting Process of Collapsing Cloud due to Gravity of its particles. Her core's Temperature is less than 10 Million K So when She Cross This temperature She will Start to fuse Hydrogen. She has to get Enough Doses to be Luminous in this process it will about 1 Million Years. The Light coming from her Just by Collapsing Gas and Dust Not by Fusion, also She is Larger Than a Star but course of time she will become Smaller when she enter in Main sequence Phase. She is still Like a Hot and Bright Dense Cloud Rather than a Star.

This is an Important point of our Star, If The Protostar Was so massive and Strong Gravity Than current time Everything Would happened Quickly it means More Massive star has Less life span. Normal Stars Form around 10 M Years, Massive Star take only a Million Year, Small Stars take Hundreds of Millions Years. Our Sun like stars Take 50 M Years. When our Star will cross Temperature of 1 Million Kelvin it will start to fuse deuterium or Heavy hydrogen, If The Protostar is not Massive Than 0.08 Ms and Never Reaches Temperature 10 Million Kelvin thus it won't be able to Fuse Normal Hydrogen. it will called a failed Star or Brown Dwarf


Disk

As The Cloud collapses it Start to Rotate and course of time it gets flat.
Even Though our star Has Strong Gravity But Still she can't swallow all the Gas and Dust Because Stars have a limit About 200 Ms (solar Masses). This means If a Protostar Reaches 200 Ms Then It will generate Very strong Power and its gravity Can't sustain its internal Pressure and It will Blow Like Little Nova and Star will die. That's Why They Can't Become Much larger and the Surrounding gas spins around it. the Particles in the disk are constantly moving.


Jets


When Collapsing Cloud Rotates it forms a Strong Magnetic Field and The Magnetic Field Also Generates Stellar Wind Which Flows in the Outer Space. Normally There is Two jets which comes from Rotation Axis of protostar. When our Star will get enough mass and pressure Eventually These Jets and Strong Winds will blow out the Shell of These Gas and dust. By helping Jets and Winds, our baby star break the portion of nebula and She will Start to Float in interstellar Medium.

Just like Hatching a Chick From egg or Ejection of Baby from its mother's Womb :)

Our Baby Star is almost Complete and the Surrounding Gas and dust will Also collapse by their Self Gravity. This will called Planetesimal, Means They are the building Blocks of planets and moons.
If there is enough material, First Gas giant then rocky planet will form because Usually Gas giants have much more gravity than Rocky planets. For many Million years These Particle will Constantly Moving, Colliding and Conjugating and Again Crash from other Particles. Course of time They will Get size of a Little Piece of rock.




In this Image We have Our star and Its Proto-Planets They will still Collide with each others and After Very Long time They Will gain the size of Earth and moon. Maybe Jupiter like Giants forms in Cold Regions So that They Still Suck the Gas and Don't create any piece of stone means They should Remain in Gas state.

After 50 More Millions of years, Our Star Looks like this image, It was Glowing in White orange Color But I have took its screenshot in a more Artistic way. it is an F type Star

So Here I have Explained All of process that are involved in stellar formation.

As We Mentioned in Section - Triggers for Stellar Formations, There was Written Stars can Form Automatically, Well This is not true generally.

But We still Don't know How The First Stars were born, Was They Form without Any trigger Because In Early Universe There was not much objects like Nowadays, Supernova Can Start the Stellar formation when its Shockwave and Radiation Arrives and Crosses inside Molecular Clouds but It is supposed There was not enough time For Birth of a star and Death. Maybe The First Black Holes helped the Evolution of those stars or maybe the Dark Matter.

Perhaps dark Matter Created The First Stars and Galaxies together just as Binary or Multiple stars System Forms in a cluster. However There is ongoing Research on the First stars formed despite of No Supernovae or any trigger like That. Black holes do Also Exists From Early Ages of universe. There is a lot of questions and there must be answer.


Anyway, Thanks for Reaching This guide and Reading. I wanna Say thanks again Who made those Beautiful Model of Nebulae.

I hope You enjoyed the Guide

Have a Nice day

Thank you very much :))