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The Sun

The Sun is the main source of energy on the Earth which provides heat and light for life. The Sun is the biggest astronomical body in our solar system. The Sun is the star around which the earth and other planets, comets, asteroids etc are revolved. It is composed of about more than 99.8% of mass of solar system. The distance between the sun and the earth varies as the earth moves from perihelion to aphelion. The sun rays take 8 minute 19 seconds to reach on earth.

Properties of Sun

  • The sun is the main sequence G2 star in universe.
  • At present sun is composed of 73% hydrogen and 25% helium of mass with about 2% of heavier elements like oxygen, carbon, neon and iron.
  • Diameter of sun is 1.39 million km with density 1.41 that of water.
  • Rotation period of the sun is 25 days 9 hours. Speed of rotation is higher on equator than on poles. Near the pole rotation time is 36 days.
  • Rotation speed of the sun is 7179.73 km/hrs while earth’s speed of rotation is 1675 km/hrs.
  • At every second, the sun fuses 600 million tons hydrogen into helium and converts 4 million ton mass into energy.

How the Sun was formed?

The Sun is also a star just like of 100 billion stars in the milkyway galaxy. The Sun was formed from gravitational cloud of dust and gas called Nebulae before 4.5 billion years when other planets and stars were formed. As the hydrogen in core is exhausted, nuclear fusion will start in surrounding layer of core and star becomes brighter and when the fusion will reach to the outer surface the Sun will turn into Red Giant. The Sun composes hydrogen and helium in its body as main fuel. It has nuclear fuel enough to last long about next 5 billion years. After that it will convert into Red giant. After that it will shed its outside layer and will become with dense cool core and become white dwarf.

According to calculation, the sun becomes 10% brighter by every one billion years. By this the sun is 40% brighter when it was on born.

Sun’s Orbit and Rotation

The sun is gaseous sphere and also it rotates about its axis. The sun takes 25 days 9 hrs to one spin at equator and 36 days at poles.

The sun is located on orion arm of milkyway galaxy having 25000-28000 light years from Galactic Center of the galaxy.  Though the sun and other planets, comets, asteroids etc. rotate the center of galaxy with 720000 km/hrs velocity, they take 250 million years to complete one revolution.

Structure of Sun

The Sun’s internal structure consists of Core, Radiative zone and Convective Zone.


It is the inner most part of the sun which cover about 25% of the sun’s radius. The pressure and temperature in core is enough to do fusion of hydrogen into helium which causes to release heat and energy. Gradually helium accumulates in core. The density of the core is 150 gm/cm3 and temperature is about 15.7 million K. About 99% energy is generated from core by nuclear fusion.

The nuclear reaction called proton-proton (p-p) chain is going on in core to generate energy. Every second 9.2 X1037 times p-p chain occurs which fuses 3.7 X 1038 protons into helium nuclei. Four protons convert into one helium nuclei with releasing 0.7 % of used mass as energy.

Radiative Zone

Outside of the core and upto 70% of Sun’s radius in which energy transfer is possible by radiation process. This portion of the sun is called “Radiative Zone”. Temperature drops from 7 million K to 2 million K in this portion.

Convective Zone

The portion from 70% of the sun’s radius to outer visible surface is known as “Convective zone”. In this portion the plasma is not sufficient dense and hot to transfer heat by radiation. The material near the techocline gain heat and expands. Thermal cells carry heat towards the Sun’s photosphere and there they become cool and increase the density and shrink toward the techocline and again gain heat and cycle is continues going on.


The layer between radiative zone and convective zone is known as “Techocline”. There is large shear between two zones due to rotation of each layer which creates Sun’s Magnetic Field.

Atmosphere of Sun

The Sun’s atmosphere consists of Photoshere, Cromosphere and Corona.


“Photosphere” is the outside visible layer of sun from which protons escapes the sun and become radiation called Sun light. Temperature of this layer is 6000 K. The photosphere’s thickness is about thousands of kilometer.


The outer layer above the photosphere about 500km thick which is coolest layer of the sun is called “ Cromosphere”. The temperature is significantly increases as height in this layer. From protosphere with increase in height it reaches from 6000 K to 4100 K and then after that it increases to 35000K at corona.


The outermost layer of sun which is extends to millions of kilometre is called “Corona of sun”. It is not visible due to extreme bright light of the sun. There is strong ionization in corona which cause the temperature in corona more than 1000000 K. Due to the magnetic field of the sun, size and shape of the corona is varies. Due to low density even high in temperature the heat is low. It is visible on solar eclipse and rosy red in colour.

What is Solar Wind?

The Solar wind is the stream of charged particles mainly protons, electrons and alpha particles released from the sun’s outer layer Corona. The speed of the solar wind may be 250 to 750 km/s having the temperature about 1 million oC.

End of the Sun

The Sun is also a star just like other star in the universe so end of the sun is undeniably. The sun was born before 4.5 billion years ago and in current days the sun has enough fluid in it to live next 5 billion years. In sun’s last time, helium in it will start to convert into heavier element and the sun will start to swell and become large enough to cover the earth and after that it will become red giant and after it will become white dwarf and end of the sun will done.

Have a great day !!!

ShakeTheMind View All

Authored by BK Suthar.
This site is about various topics of astronomical and geographical things which present in universe and also surrounding us. It will give you information about various planets, incidents occurs in universe and also about nature.

Have a good day !!

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