t is no exaggeration to say that we all owe our lives to the Sun. Being the heart of our solar system, it provides light and heat – without the energy output of the Sun, the Earth would be frozen solid. Actually, the Sun is an ordinary star, and like all stars, it can create a massive volume of energy from a process called nuclear fusion.

Basic anatomy of the Sun

Before plunging into the topic of the Sun energy output, let’s start with the basic structure of the Sun.

The Sun is composed of different layers. The major inner layers are the core, radiative zone, and convection zone. The core, which is the innermost layer of the Sun, is the region that extends from the center to about 20–25% of the solar radius. The visible bright outer layer is called the photosphere.

The Sun is a giant ball of very hot gas. Most of this gas is hydrogen (about 70%) and helium (about 28%).

Where does solar energy come from?

The energy output of the Sun, both heat and light, originates from a nuclear fusion process inside the core. It is a nuclear reaction where two light nuclei collide to form a single, heavier nucleus. The resulting energy travels outward from the core of the Sun and moves across the solar system.

In the core, the temperature and the pressure are high enough for hydrogen protons to fuse and turn into helium, releasing tremendous amounts of the Sun energy output. Out of all layers of the Sun, the core has a crucial function in producing heat, as it contributes 99% of the fusion power.

The zone immediately next to the core is called the radiative zone. This zone transfers the Sun energy output generated in the core outward to the upper inner and outer layers as radiation.

In the convection zone, the energy output of Sun is transferred to the photosphere through convection currents. The surface of the convection zone is the place where light (photons) is created.

Last but not least, there is the photosphere, the outer layer of the Sun. It is here that the Sun energy output propagates out into space and reaches Earth's atmosphere. The Earth absorbs most of the energy output of Sun, and a small fraction is reflected back to space.

The energy output of Sun is enormous – the Sun produces about 3.94 X 10 23 kW daily. It is hard to believe, but every 1.5 millionths of a second, the Sun releases more energy than all people consume in an entire year! Undoubtedly, the importance of the Sun energy output for humankind is difficult to overestimate.

Mar 31, 2023

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