Energy Resources

1.7.3 Energy released by nuclear fusion in the Sun

The Sun is a massive star that produces an enormous amount of energy. This energy is released through a process called nuclear fusion that occurs in its core.

What is Nuclear Fusion?

Nuclear fusion is the process where two or more atomic nuclei combine to form a single, heavier nucleus. This process releases a tremendous amount of energy because the mass of the resulting nucleus is slightly less than the sum of the masses of the original nuclei. This 'missing' mass is converted into energy according to Einstein's famous equation:

$$E = mc^2$$

Where:

• E is the energy released
• m is the mass defect (the difference in mass)
• c is the speed of light (a very large number)

Fusion in the Sun's Core

The Sun's core is incredibly hot (around 15 million degrees Celsius) and under immense pressure. These extreme conditions allow hydrogen nuclei (protons) to overcome their electrostatic repulsion and fuse together. The primary fusion reaction in the Sun is the proton-proton chain, where hydrogen nuclei combine to form helium nuclei.

A simplified representation of the proton-proton chain is:

$$ 4 \text{Hydrogen} \rightarrow 1 \text{Helium} + \text{Energy} $$

This fusion reaction releases vast amounts of energy in the form of:

• Kinetic Energy: The newly formed helium nucleus and other particles (like positrons and neutrinos) have high kinetic energy.
• Electromagnetic Radiation: This energy is released as electromagnetic radiation, including visible light, infrared radiation, and ultraviolet radiation. This is the light and heat that reaches the Earth.

Why is the Sun's Energy Important?

The energy produced by nuclear fusion in the Sun is essential for life on Earth. It provides the heat and light that sustain our planet's climate and allow for photosynthesis in plants.

Table Summarizing Nuclear Fusion in the Sun

Process	Reactants	Products	Energy Released
Proton-Proton Chain	Hydrogen nuclei (protons)	Helium nucleus, positrons, neutrinos, photons	Enormous amount of energy (heat and light)