Combustion as we define it requires oxidation of fuel. I.e. burning of fuels like wood and hydrocarbon fuels with oxygen from the atmosphere in a chemical process to produce heat.  The process of heat generation in the sun is due to the combination of hydrogen atoms into helium by fusion, a nuclear process.

The heat and light coming from sun is not because of burning of some substance as we think , but it is because of a process called nuclear fusion . Therefore , the heat and light coming from sun is not considered as combustion .

The Sun: A Source of Light and Heat

The sun, our nearest star, is a constant source of light and heat for our planet. It plays a crucial role in sustaining life on Earth, providing the necessary energy for various biological processes and driving weather patterns. However, the sun's light and heat are not a result of combustion but rather a consequence of nuclear fusion occurring in its core.

Nuclear Fusion: The Powerhouse of the Sun

Nuclear fusion is the process in which two or more atomic nuclei combine to form a heavier nucleus, releasing an enormous amount of energy in the process. In the sun's core, temperatures and pressures are incredibly high, allowing hydrogen nuclei (protons) to collide with each other and merge, forming helium nuclei. This fusion process releases an immense amount of energy in the form of light and heat.

The Sun's Structure and Fusion Process

To understand how the sun produces its own light and heat, let's delve into its structure and fusion process:

1. Core: The sun's core is the central region where fusion occurs. It is incredibly hot, with temperatures reaching about 15 million degrees Celsius. The pressure at the core is also extremely high, allowing for nuclear fusion to take place.

2. Radiative Zone: Surrounding the core is the radiative zone, where energy is transported by photons. Photons are created in the core through fusion reactions and then travel through this layer, gradually losing energy as they interact with other particles.

3. Convective Zone: Beyond the radiative zone lies the convective zone. Here, energy is transported through the movement of hot plasma. Rising hot plasma carries energy towards the surface, while cooler plasma sinks back down, creating a cycle of convection.

The Sun's Energy Output

The energy released through nuclear fusion in the sun's core takes the form of electromagnetic radiation, or light. This radiation encompasses a wide range of wavelengths, including visible light, ultraviolet radiation, and infrared radiation. These different wavelengths of light are responsible for the various effects of sunlight, such as heating the Earth's surface, enabling photosynthesis, and causing sunburns.

Conclusion

In conclusion, the sun's light and heat are not the result of combustion but rather the outcome of nuclear fusion occurring in its core. Through the process of fusion, hydrogen nuclei combine to form helium, releasing an immense amount of energy in the form of light and heat. Understanding the sun's structure and fusion process helps us appreciate its role as a self-sustaining source of light and heat, crucial for supporting life on Earth.