Have you ever heard a star belongs to this or that category and wondered What the heck is this? If this question bothers you, then you have come to the perfect place where we talk about the Cosmos, and not only we talk about astronomical objects and structures but we make it easier to understand so that Common folk can easily comprehend such things. most people find this subject extremely hard but Don't worry we will give you information the easiest way possible. So welcome to our Blog where we make astronomy not only easy but for all, yes anyone can enjoy this interesting knowledge. Thanks again for reaching out here.
Let's Start
Introduction :
You may have seen numerous Stars in the night sky, varying in color, distance, and properties and nowadays you may have also heard that the x star is about to explode, the y stars are dangerous for Earth and the z star is a very good spot for living in its planets, etc. Scientists are looking for life around these stars of course that's not an easy task. Some people have many misconceptions about such scientists and their discoveries. In our blog, we'll try to remove that misinformation and provide a clearer vision to understand their aim and project. In this post, we'll discuss a scheme called the Morgan - Keenan System or Yerkes system Named after its inventors.
If you read this post carefully you will be able To :
1) Understand the Star's characteristics like Mass, Temperature, Magnetic field, Radiation, and many more.
2) Know basic properties like their abundance and whether they are harmful or not just by hearing the categories.
3) What kind of planets would there be and will we survive?
Alright, Let's know how they are categorized.
First of all Star's category consists of a Letter, a number and a Roman Number which are assigned with an eye to the Characteristics of a Star let's know about them.
The Letter :
As soon as a star emits energy in the form of light and heat from its
photosphere (the part which emits light) it sets out in space at
300,000 Km/s but light's journey doesn't go uneventful, sometimes,
its photon (particle of Light) absorbed or captured by Electron, proton,
neutron, and other subatomic particles, when such particles emit the
photon it gets more or less changed in some aspects. You know stars are
located at enormous distances their distance is measured in Light years
meaning When light travels at its basic speed in one year this distance is
called one Light Year. this is a very long distance and after their long
journey when they reach Earth and our eyes, we can see the star, that's
pretty simple.
But in Their extremely long journey and time, various things can happen and
it does, the produced light from the star and the light as we see are not
the same, they interact with the other atoms, molecules, Photons from other
stars, nebulae, planets, gravitational, electric and magnetic fields there
so many factors which can change the Light's behavior. An instrument called
the spectroscope, spectrometer, or spectrophotometer whatever you say
they are almost same with little differences, when a spectroscope analyzes
the Light of a star and it splits into 7 color rainbow thing called the
spectrum, then scientists see which wavelength is dominant in the spectrum,
at least you should know that if you change the wavelength of light it will
change the color. for example, 500 nm will appear in green, 750 nm will be
red and we will perceive 400 nm as violet color but these are only for human
eyes.
Scientists find which type of light is being emitted
mostly on the spectrum and then they assign a certain letter for that
star, We should know Stars emit all kinds of Radiation but we only look for
the Most prominent one this way we can know star's properties. So those
letters can be: O B A F G K or M
You can look at this table :
Our Sun emits all kinds of radiation but yellowish-white light is
mostly prominent in the spectrum so We say our Sun will Belong to
G Class.
One thing you need to know these colors are only for denoting their light
Meaning Hot Star emits blue light and Cool stars shine in red-orange
colors. If you look at them in space, they will not probably appear in the
color shown in the table because there are environmental, Physical, and
other factors that will render stars in more or less different colors. for
example, The Sun Like Star comes in Yellow or G Class but when you look at
the sun with your own eyes it will appear white moreover if you see it in
the morning or evening or in other conditions like Overcast it will appear
different. So don't be confused if they aren't looking exactly as shown in
the table.
The Number
After Assigning the Letter, we see in the table the G Group can consist of
Stars with temperatures around 6000 - 5200 K. this is a large range in
itself even though Two Stars with 6000 K and 5200 K may appear similar
nevertheless they will show a variety of properties. It means we need to
further divide the G group So we will use numbers.
Numbers can be 0 to 9 in a spectral class or letter where 0 is the hottest
and 9 is the coolest in a group. this is also known as hot (early) and
cool (late) words. Studies show that our sun's surface temperature is
about 5800 K, so number 2 is assigned by scientists so we get G 2 here for
our sun. the further we go with numbers we find that K5 is hotter than K6
but Cooler than K4, likewise F2 is hotter than the entire G, K, and M
class but cooler than A9 star you can understand now how easy it is.
The Roman Number
Once we decide letter and number, Scientists need to know its
luminosity so the greater the star's luminosity smaller the Roman
number will be. For example, If a Star is mostly stable and Fusing
hydrogen and converting it into helium, generating enormous energy we
call it the Star's 'Main Sequence Phase' or its productive phase where
stars spend most of their lives. however, Star can produce energy in
other phases but they are not considered stable and they are
relatively shorter than the Main sequence. such characteristic is
determined by the width of absorption lines in their spectra which
occurs when a certain element absorbs a particular wavelength of
light.
You can see in the table below :
So for our Sun's surface, the temperature is about 5800 K, it
gets G2 and it is currently in the
main sequence phase meaning it is producing energy and stable
too, according to the table it will get V for the Main sequence.
Therefore Sun is a G2 V Type Star.
Brief Description of Spectral Groups :
Let's see some major Characteristics of these Classes and the Main
Article's Link is on their Title.
O Type Star :
It contains upper extremities of stellar characteristics eg. Mass,
Temperature, and so on. They are very rare to find, these are usually
16 times more massive than our sun, lasting only a few million years
due to high-speed fusion. Their core is powered by CNO Cycle which
allows them to burn Hydrogen and helium so fast and produce various
elements. in supernova explosions, they scatter all those elements
through their remnant nebula. They are powerful sources of Ultraviolet
Rays and they don't support any planetary systems because they often
interrupt planet formation in Nebulae. Human life is not possible in
every way.
B Type Star :
They Are slightly easier to find than the previous category: and have
lesser properties than O - Class but they are 2nd Most powerful group
of stars. Less massive stars become Powerful White dwarfs after death
but mostly they also become supernovas. since they have less mass,
they Fuse their fuel not as fast as the previous group and have a
longer lifespan. The Majority of Blue Stars belong to this group and
Like O Type Stars their fusion is also powered by CNO Cycle. They also
lose mass like its powerful version and show very strong winds and
magnetic fields.
A Type Star :
These Stars are slightly more abundant than the previous two
categories hence there are so many stars in the solar system
neighborhood. they are also hot and bright, glowing in Blue and White
light. Some A Stars are surrounded by a Debris disk similar to
Asteroid and Kuyper belts in our solar system hence they can host a
planetary system. CNO Cycle powers the Fusion, They are also great
emitters of Ultraviolet but in less amount than O and B Stars.
F Type Star :
F class contains intermediate-mass stars that shine in Yellow and
White color, they are more abundant than previous categories. Their
fusion uses Both CNO and PP Chain methods to keep the star for a few
Billion years, they are relatively cooler than previous categories.
Ultraviolet and other harmful radiations are not harmful as other
massive stars so scientists are trying to find some habitable planets
around such stars. since their mass is low enough to keep everything
balanced. These kinds of stars rarely become supernovas instead they
lose outer layers and create planetary nebula, core becomes a larger
white dwarf than our sun's core will.
G Type Star :
They are even cooler stars, glow in Yellow and White color, abundant
in local space. Mostly PP Chain Dominates the Fusion and CNO is also
present but in a Minor way. Our sun is a member of this group.
Ultraviolet is not so powerful and supports planetary systems. They
have large habitable zones meaning there is enough distance from the
star so water can stay in liquid form. they show little mass loss as
compared to higher groups therefore they have a lifespan of many
billions of years. they follow the same path as F Stars.
K type Star :
This group is known for being beautiful stars for human life because
they are durable and stable and show very few stellar activities, even
than G Type. CNO exists only in High mass Stars hence PP Chain is the
Primary source of Energy. There are so many popular stars from this
class. there are so many planets around them and also in the habitable
zone, they have less harmful Ultraviolet radiations and they glow in
Orange and yellowish white color. they also follow the same fate of G
and F stars.
M Type Star :
These are the coolest stars but not that cool you can walk their
surface, Their main sequence phase is very long sometimes it can
last several Billion to Trillion years, also they are pretty small
and least massive meaning they Burn the hydrogen slowly and
efficiently. Fusion is powered by the PP chain (Proton-Proton Chain)
so they slowly fuse their fuel and can convert 95 - 100 % hydrogen
into energy. Their magnetic field lines are so densely twisted. show
magnificent stellar activities like Coronal Mass ejection and flares
etc. They are very abundant in local space. Many planets are also
confirmed around such Stars.
Those were the Main Categories of Stars but Tale doesn't end here, we
have a lot of things to know about stars. In their heading Links, We've
been able to go into greater detail, If you are interested just click on
them and enjoy learning.
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