Have you heard about Population III stars ?

If you Hear word Population probably you may think the Number of stars in space

Well, That's not at all.

we humans use a word called population for Counting people on earth / Country / Area or Anywhere

But

Scientists Uses this word for Indicate Age of the Stars.

in space, There is Very huge number of stars, Each of them have their own Characteristics and many are Same in some respects and features Scientists use Current Generation of stars in MK System but that is for their spectral properties and can tell many other interesting facts However There is no class for their age Groups. That's why there is Word Population or Generation of stars

Before We discuss any further we will know How Age is determined of star Briefly.

Well How this is Possible, Knowing Age of star ?

A star which is Always Shines in Day and Night and nobody knows how old they are ?

Ask your Grandpa they would say This question I also asked to my Grandpa and Said I Was watching it since my Childhood.


Well, The age of star is measured in numbers about in Millions to Billions as usual, These numbers are not Correct or should we say These are Estimations only and those number gives us a surface to think over on. Actually Nobody can Know Age of a star So they can only Predict the Estimation of age Which seems Pretty Close to Actual age of stars.

They Can Do it By measuring the amount of Chemical Elements, By percentage of fuel and Amount of the Product in the star's core. Which comes from its Light / Radiation and Using Spectrometre or Spectrograph or Such Instrument which is able to Isolate Different radiation lines from other Molecules of elements Of course they only estimate and Calculate How much These Element dominant in that atmosphere of Which is being study

All these calculation are based on the Spectral lines of the stellar Radiation and Such Elements form Thousands of years of Fusion, So this can be best idea to Identify the Age of star.

For Example.

in case of a Giant blue or Red Star or Wolf - Rayet Star Fuse their hydrogen and Make Helium Nuclei After some Thousands or Millions of years it will fuse Helium when it will also exhausted it'll
Fuse Carbon after that Neon and then Oxygen, This process Continues Because They have Enough Temperature and Pressures so this is like a Produce the Element and Use it as fuel and Then Use the Product after product Too. Also these element Accumulate and Forms a Shell like structures as an Onion when These Element Generate Energy by Fusion the light comes out and reaches near our Satellite and Examine its properties Through Spectrum and Count the amount of those element and Estimate its Age.

So Most of the Stars Burn / Fuse their hydrogen Nuclei in most of their life Times but They Are Also Able to Fuse Various Elements.

But in many case Most of the Stars Can't Fuse the Iron Nuclei Because Iron will take Much more energy and Give Less energy than Lighter elements.

As the Star Burns its hydrogen to helium it releases Enormous Energy but If it start to fuse heavy elements than these both the energy will Release in Slightly less amount. That's Why The Iron is the Limit for Fuel. in other words Star Fuses normally Hydrogen to Iron.

The star can't Fuse Iron Before Becoming a Supernova Normally.

In astronomy, To Classify the star by their age, Population Word is used.
So There is Three Population of stars actually one is Theoretical.

Metallicity is used for How much metals present in that star, To denote it there are Several Methods, Some are calculated by Complex Maths and Chemistry Formulae or Just by comparing From our Sun.

Metals are terms for Describe Any other Element than Hydrogen and helium, Just for example We know Oxygen and Nitrogen are gases or Non - Metals But in Astronomy it will defined as Metals.
So don't be confused by Metal These are not that type of elements That we know or found in earth
They are just their Isotopes or Similar Elements because inside of a star there are a lot of other Element's Variant Forms and Destroy same time but Stable of them are classified as Elements or Metals if they are other than Hydrogen and Helium.

Sometimes they are also called heavy element Because they have More Atomic Mass than Helium and Hydrogen.

These stars have High Metallicity or constituted by many Other kind of Metals. These are also Called Metal Rich Stars

They are common and Contemporary Stars and We See most of the stars and we know them.
This kind of stars have Distributed in almost Every Galaxies and Specially Found near and in Galactic arms. They are common Ingredients of Elliptical Galaxies. They orbit the Galactic Centre in Elliptical path. They also Consists planetary System in fact Planet around these stars are very common Than other Two Stellar Populations Because They have formed in Metal Rich Nebula Thus After creating the star The Rocky planets and Gas giants also forms From the Rest material.



Our Sun is Population I star

These are Metal - Poor Stars, Means they have not sufficient Metals or Low Metallicity Than Previous Category.

These stars Were Formed in Earlier Stages of Universe and Slightly Rare than Population I stars, However These Might Appear in Galactic Bulge and Certain Globuler Clusters. They are oldest Stars That means If any Population II star found, most of the chances are it would be in Red Giant phase or Maybe Black hole or Neutron Star or Have Formed Supernova remnant nebula.

This kind of stars Create Type Ia and Type II Supernovae.

But There is still Some Stars Which are Population II or Metal Poor Stars

some of them Are :

Sneden's Star, Cayrel's Star, HD 122563 ( red giant ), HD 140283 ( sub giant )

it is said,

After Some thousands of years of Big Bang, There was Everywhere Extremely Huge, Hot and Dense Clouds of Hydrogen and Helium and When the Atoms of these clouds Collapsed due to their Mutual Gravity and Started The Process called Nuclear Fusion and The First stars Formed, They were Used to Extremely Larger than Any kind of Present Giants and they Fused Their Hydrogen So quickly in almost few Million Years only.

During Their Death, They Created Large Supernovae and Supermassive Black holes and It is Thought The First 26 Element in Periodic Table of chemistry, Was Created by such stars. They were Metal Zero Stars.

There was Some Minor Reports of Presence of This type of Stars But in general You can think these are Fossils of Star That they were Existed in early universe but not now or Very difficult to Find



There is no Direct Evidence of Population III Stars :)

So those were Stellar Population Groups, If you are Thinking about Pop - III Stars then I wanna Tell you These are Hypothetical Stars To Explain How The Supermassive Black holes Grown Quickly Since Universe is not too old So that They Can Become From Stellar Massive to Super massive.
We still don't know The First Star were Large or not. These Are Just Theories and Can be true if there is Actually a Pop - III star or such a Remnant Found.

So that's all for this guide

Thank you for Reaching and Reading This guide.

See you again in Another Tremendous Guide. Good Bye. : ;)