Contrary to what many believe, the star does not burn like fire here on Earth. For there to be fire, free atmospheric oxygen is needed, an element that is abundant on our planet, making up 21% of the atmosphere. In contrast, space, known for its almost absolute vacuum, contains trace amounts of oxygen, insufficient for any kind of combustion, as explained by the European Space Agency (ESA).

Burning on our planet

For example, we can use the process of a piece of paper, which, when set on fire with a match, begins a process in which the atoms in the paper, rich in carbon, hydrogen and oxygen, react with atmospheric oxygen. This encounter produces carbon dioxide and water, releasing energy in the form of heat and light. This process is known as combustion.

So what makes the sun burn endlessly?

The Sun operates by a completely different process, called nuclear fusion, which occurs without the need for oxygen. In the core of the Sun, where the temperature reaches 15 million degrees Celsius and the pressure is extremely high, hydrogen atoms fuse to form helium.

In this impressive process, the Sun converts 700 million tons of hydrogen into 695 million tons of helium every second, releasing energy in the form of gamma rays that eventually turns into the light and heat we receive.

In other words, the Sun radiates light and heat not because it “burns” like fire, but through nuclear reactions that occur under conditions of extreme heat and pressure.

But if space is almost empty, how does the sun's heat reach us?

The heat that we feel on Earth is not a direct transfer of solar heat, but rather a transfer of solar radiation. This radiation, which includes visible light and other wavelengths of the electromagnetic spectrum, passes through the vacuum of space, interacts with particles in our atmosphere, and turns into heat that we feel.

Although the Sun has used up about half of its hydrogen reserves during its 4.5 billion years of existence, it still has enough “fuel” to continue shining for another few billion years. This process of nuclear fusion is not only vital to the Sun's production of energy, but it also explains why the Sun does not need oxygen to “burn.”

So, next time you see the sun glowing and feel the heat, remember that you are witnessing an incredible nuclear reaction, a cosmic spectacle of atoms that produces the light and heat that supports life on our planet.

Author: Felipe Espinoza Wang

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