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About 4.6 billion years ago, in some forgotten corner of the Milky way when a cloud of dust and gas called a nebula collapsed under its own gravity, the sun and other planets were born.

The sun
Image1: The sun

Our home star The Sun is the one the average size star in the billions of the stars in the universe, but it is a special one because it provides life on the earth.

The sun somewhat 26,000 light years away from the Milky Way’s center and located at Orion arm of the galaxy.

solar system's location in the Milky Way galaxy.
Image2: Location of the sun in the Milky Way galaxy

The sun contains 99.8% of the entire solar system’s mass. The sun along with all the planets, moons, and asteroids in every 230 million years, makes one orbit around the Milky Way’s center with an average velocity of 450,000 miles an hour.

Surface and Structure

The sun contains 99.8% of the entire solar system’s mass, containing primarily elements hydrogen and Helium of 70.6% and 27.4% respectively. In terms of the number of atoms, it is made of 91.0% hydrogen and 8.9% helium. The Sun’s structure has six regions: Core, Radiative zone, Convective Zone, Photosphere, Chromosphere, and Corona.

Sun's structure
Image3: The structure of the Sun

The innermost Region the Core occupies 20 to 25 percent of the sun’s radius, where immense pressure and temperature, produced by the gravitational attraction of the sun’s enormous mass; are sufficient for nuclear fusion. Nuclear fusion fuses hydrogen into helium and releases a staggering amount of energy. As a result, helium gradually accumulated in the sun’s core. At the core, the temperature is about 27 million degree Fahrenheit (15 million degree Celsius) and density up 150g/cm3.

The immense energy produces by the sun’s core is carried outward by radiation, which bounces around the radiative zone. These energies take 170,000 years to get out from the core to the top of the convective zone. In addition, the density drops 20 g/cm3 to 0.2 g/cm3 from bottom to top of the radiative zone. The radiative zone and convective zone are separated by a transition layer called –“Tachocline”

The energy in the convective zone is in the form of a large bubble of hot plasma move upward with a temperature of about 3.5 million degree Fahrenheit and the density drops to 0.2 g/cm3.

 The Photosphere is the Region of the sun which we can directly observe with visible light. The temperature in this region is about 10,000 degrees Fahrenheit. Most of the solar radiation is escape outward through the photosphere (the surface of the sun). It is around 500 km thick.


The sun’s atmosphere is composed of four distinct parts – the chromosphere, the transition region, the corona, and the heliosphere. These parts are seen during a total solar eclipse when the disk of the sun is covered by the earth’s moon. This is a region where we see features like sunspots and solar flares.

Filamentary nature of plasma connecting regions of different magnetic polarity
Image4: Filamentary nature of plasma connecting regions of different magnetic polarity

The chromosphere is about 2000 km thick and its temperature near the top of the chromosphere is about 20000 kelvin. In the upper part of the chromosphere, helium becomes partially ionize and the chromosphere looks a Red rim around the sun.

Above the chromosphere, a thin layer of transition region found of thickness about 200 km. The temperature of this region varies from 20000 kelvin to 1,00000 kelvin.

The next layer of the sun’s atmosphere is Corona. The average temp of the corona is about 1 million to 2 million kelvins; however, the hottest region is 8- 20 million kelvin. Strangely rise in temperature with in sun’s atmosphere with altitude has been a scientific mystery for more than fifty years.

Orbit and Rotation

The suns along with eight the Planets, asteroids, and comets somewhat 26,000 light years away from the Milky way’s center and located at Orion arm of the Milky Way galaxy. From there Sun orbits the center of the Milky Way galaxy with an average velocity of 720,000 km/h. But even at this speed, it takes about 230 million years to make a complete orbit around the Milky Way. Presently Sun is moving in the direction of the constellation of Cygnus.


Sun's size comparison with the earth. The sun is 109 times wider than earth.
Image5: size comparison of the Sun with the earth

Our sun is about 1.4 million km wide, approx 10 times wider than Jupiter and 109 times wider than the earth.

The volume of the sun is 1412×1015 km3. If it was a hollow ball, about 13 Lac earth could fit inside the sun. But the sun is not hollow ,it contain 74.9% hydrogen and 23.8% of helium and less than 2% of mass contain oxygen (1%) ,carbon(0.3%), neon(0.2%), and iron (0.2%).

Distance and size Between sun And earth
Image6: Distance and size Between sun And earth

The Sun gravity is too huge about 274m/s2 that holds the solar system together, keeping everything from the biggest planets to the smallest particle of debris in its orbit.


In the heart of the sun’s core nuclear fusion converts hydrogen to helium, this generates high energy Gamma-ray photons. These photons almost immediately absorbed by the solar plasma of the radiative zone. As a result of this sequence of emission and absorptions, hot plasmas take a long time for radiation to reach the sun’s surface, called the photosphere. It can take 170,000 years for a photon to complete its journey out of the sun, but once it exists, it zips through space at more than 186,000 miles a second.

Approximately 600 million tonnes of hydrogen are converted into helium every second, releasing energy at a rate of 3.36×1026 joules per second. Yet the sun is so large that it has been burning hydrogen at this rate ever since it formed some five billion years ago, and it will continue to burn steadily for at least another four billion years.

The solar energy striking the earth is equal to 800 billion megawatts of power, an amount vastly more than the entire capacity of all our power plants.

The temperature at the sun’s core is about 27 million degrees Fahrenheit but at the surface, it is about 5778 kelvin.


The Sun has a strong and complex magnetic field, which is generated by electric currents; varies across the surface of the sun. The volume of space controlled by the sun’s magnetic field is called the heliosphere.

The magnetic field of the sun also varies in time and location. Approximately every 11 years, the sun‘s geographic poles change their magnetic polarity and during this sun’s photosphere, the chromosphere and corona behave violently and release huge amounts of energy and particles.


The sun has no moons, However the sun has the Planets, the Planet’s moons, Asteroids, Comets, and Other materials; orbiting the sun.


The sun has no Ring.


The sun does not support life, because it is a very hot, energetic mix of gases and plasma. But due to the sun, life is possible on earth.

Human touch:

A number of spacecraft launched from the earth’s surface to study the sun’s magnetic field, corona, sunspot, solar flares, etc. But Parker solar probe mission is revolutionizing our understanding of the sun. The primary science goals for the mission are to trace how energy and heat move through the solar corona and to explore what accelerates the solar wind as well as solar energetic particles.

The latest on going mission is a solar orbiter launched on Feb 2020 to study the heliosphere. Isro has also planned to send orbiter by 2020 to study solar corona.

Quick Discover :

the sun

Star Type:

Yellow Dwarf

Distance from the center of the milky way: the sun:

27,200 light years

Distance from the earth:

149.6 million km | 1 Astronomical unit


695,508 km

Escape velocity:

617.7 km/s

Equatorial rotational velocity:

7.2 x 103km/h

Surface gravity:

274 m/s2

Mean density:

1.408 g/cm3


1.98×1030Kg (333,000 x earth)


No moon


No ring

Potential for Life:

No life

Image credit :





Image6: universediscover/aniketkumar


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