How does sun produce Energy?

From the time of immortal the sun has been the prime source of energy for all the living beings on the earth. Without the sun and its energy the planet would have been a cold lifeless chunk of rock. The sun’s heat warms the oceans which is very essential for the water cycle. It drives photosynthesis on earth which makes plant grow. Furthermore it heats the earth’s atmosphere which directly influences the climate pattern on earth which we feel on daily basis.

So it’s correct to say that sun makes life on earth possible. We use sun’s energy in many different ways. The earth only gets 2 billionths of sun’s energy, which is still a lot.

But ever wondered from where the immense energy of sun comes from? Moreover, before that the question comes what the sun really is??

What is Sun?

This is one of those 100 billion stars that present in our galaxy. It is the largest object in the solar system and makes up 99.8% mass of the solar system. It is to be believed that the sun is about 4.5 billion years old and it will probably continue to exist in its present form for about 5 billion years more.

Unlike earth which is made up mostly of rock, iron, water and many other elements, the sun is made up primarily of hydrogen and helium gas. It consists 75% of hydrogen gas and 25% of helium gas.

Temperature inside the sun is 15 million degrees Celsius. The energy output of the sun is nearly about 386 billion Megawatts which is produced by Nuclear fusion. Apart from heat and light the sun produces a stream of charged particles called solar winds.

Sun surface


How Does Sun Produce Energy?

Like most of the stars sun is composed mainly of the hydrogen gas. The easiest way to think is that sun is as a giant ball of very hot plasma, composed of around 75% of hydrogen gas, 25%of helium gas and remained places are filled with elements such as oxygen, iron, neon, nitrogen and silicon.

The process of producing energy starts from the core of the sun. The core is the hottest area of it. In addition to intense heat there is a huge amount of pressure at the sun’s core. In fact it is so compressed that enormous amount of hydrogen atoms fuse together in the process known as “NUCLEAR FUSION”

Nuclear Fusion converts the hydrogen atom in to helium. The by product of nuclear fusion in the sun’s core is a massive volume of energy that gets released and radiates outward towards the surface of sun and beyond it.

What Actually Nuclear Fusion Is?

Nuclear fusion is a reaction in which two atomic nuclei fuse together to create a large nucleus and in that process it releases energy. It’s an atomic reaction in which multiple atoms combine together to form a single more massive atom. The resulting atom is slightly smaller in mass than the sum of the masses of the original atoms.

That difference in mass released in form of energy based on Einstein formula E=mc^2, which says mass can be converted into energy. That is what exactly happens in sun. It does not take much mass to make a lot of energy. That is why nuclear fusion produces such vast amount of energy.

This reaction takes place in 3 different steps:

  • Two or more hydrogen atoms collide with each other and convert to one helium atom. Two protons combine to form a deuterium nucleus first, which consists of one proton and one neutron. During this part of process a positron and a neutrino are generated.


  • Second, each deuterium nucleus combines with another proton, forming a nucleus of helium-3 and it consists of two protons and one neutron. An energetic photon is produced during this part of the process, with a wavelength in the gamma-ray portion of the electromagnetic spectrum .


  • Finally, two nuclei of helium-3 combine to form a nucleus of helium-4, which consists of two protons and two neutrons. In this part of the process, two protons (ordinary hydrogen nuclei) are released. These protons can eventually involve in another fusion reaction.


Here it should be clearly noted that single helium-4 atom is lighter than the four hydrogen atoms that started this process to form it. So what happened to all that extra mass from the hydrogen atoms that we started out with? Well, that’s where we get the massive amount of energy given off by nuclear fusion. Fusion of two helium-3 atoms free a neutron and release 17.59 MeV as kinetic energy and the corresponding amount of mass disappears because the mass converted to energy, E=mc^2.

Fusion reaction

These fusions result in 4.26 metric tons of energy released from the sun every second. As the gravity of sun captures much of the output, so most of the energy remains within the sun. However the force of explosion caused during fusion allows some of energy to escape the gravitational pull of sun. The energy continues to taper off and weakens as it makes its way to earth’s atmosphere.

The energy finally touches the surface of earth in the form of sunlight, which is a radiant combination of light and heat.

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