Why Doesn’t The Sun Run Out of Oxygen as it Burns?

The sun is the center of our solar system and has been burning bright for 4.5 billion years. It is estimated that it will burn for another 5 billion years before shifting to the burning of helium for another 130 million years.

If the sun has been burning this long and will continue to do so, many wonder how it hasn’t run out of oxygen yet. If you want a short answer, then it is simple. 

The sun doesn’t use oxygen to burn. Instead, it has hydrogen reserves which it burns and carries out nuclear fusion instead of using oxygen.

Are you still confused? Don’t worry. The following article is going to discuss how and why the sun never runs out of oxygen. We will guide you through the sun’s burning process and what makes this shining beacon light up our sky every day.

Why doesn’t the sun run out of oxygen as it burns?

The burning of the sun is not chemical combustion. Simply put, the sun does not use oxygen to burn so it can’t run out. Instead of chemical combustion, the sun is nuclear fusion.

Many people think of the sun like a giant ball of flames, almost like a giant campfire. However, it is more like a colossal hydrogen bomb.

In the grand scheme of space, the sun is quite close to Earth but there is no need to worry. It is still far enough away for the effects of nuclear fusion to be at an absolute minimum.

All stars are full of hydrogen and work in the same way as the sun and how a hydrogen bomb would.

Difference between carbon combustion and nuclear fusion

Carbon combustion

When studying carbon combustion, it has been found that carbon atoms in the fuel move closer to oxygen atoms in the air. These then bond together to form carbon dioxide and carbon monoxide.

While this is happening, hydrogen atoms in the fuel bond with oxygen atoms and form water molecules.

The combustion of carbon and hydrogen are the main chemical reactions occurring although there are often more chemical reactions taking place in a carbon-based fire.

We experience light and heat from flames due to the energy released by this combustion. Just about every fire we see in life is carbon combustion such as campfires, candle flames, barbecues, forest fires, gasoline burning, and more.

The difference here is that carbon combustion needs oxygen to burn. When all the oxygen has gone, carbon combustion ceases.

Nuclear fusion

Unlike campfires we experience, the sun uses nuclear fusion to burn. This is when the nuclei of atoms become fused together to form newer and larger nuclei.

The atom becomes a new element because of how the nuclear of an atom determines what that atom is as well as how it behaves.

This results in a change to the nucleus and the atom becoming a new element. An example would be when two hydrogen atoms become fused together and create one helium atom.

Unlike carbon combustion, nuclear fusion doesn’t require oxygen to burn. No additional material is needed at all.

As long as there is enough pressure or heat that can squeeze the atom’s nuclei enough that they conquer their electrostatic repulsion and become bonded into one singular nucleus, nuclear fusion can take place.

The sun is like a gargantuan nuclear fusion bomb. Inside a nuclear fusion bomb, extreme temperatures and pressures are equipped by other bombs. In stars, these intense temperatures and pressures are provided by gravity.

A star’s mass is so large that any gravity made by this mass ends up crushing the star inward. This is enough to create nuclear fusion.

When this fusion takes place, immeasurable amounts of energy are released and we experience this through sunlight. The energy that is released by fusion further helps the nuclear fusion reaction to continue.

The reason our sun emits so much light is because of how hot it becomes from nuclear fusion. It has a sweltering core temperature of 16 million Kelvin with a core pressure of 25 thousand trillion Newtons per square meter.

This intense heat results in the sun glowing and shining bright just like the red glow of a piece of metal that is heated up.

How does nuclear fusion work?

There are two key forces at work with nuclear fusion. These are electromagnetic force and attractive strong nuclear force. The electromagnetic force is what causes the repulsion between two nuclei of hydrogen atoms.

Compared to the strong nuclear force, the electromagnetic force is weaker. As two nuclei become closer due to gravity’s intense pressure on the sun, the strong nuclear force becomes dominant.

It causes the nuclei to bond together and this is despite the electromagnetic repulsion. The amount of pressure needed to move atoms close enough for the nuclei to stick together is enormous.

Any two nuclei can be fused together into one singular nucleus but it is the nuclei that are easiest to fuse, and the ones that release the most energy, that have the smallest electromagnetic repulsion. This is because they have a very little electric charge.

Most of the fusion occurring within stars is hydrogen fusing with itself or more light elements.

Gravity provides the pressure needed to begin nuclear fusion in stars and, as gravity is caused by mass, all that is needed is a large enough hydrogen mass to ignite burning stars.

Although stars don’t use oxygen to burn, there can be very small amounts inside but these are created by hydrogen repeatedly fusing until the formation of oxygen happens.

Importance of gravity

Gravity is vital in the fusion of stars. Larger stars have a greater mass so the gravitational force acting inwardly on the star becomes far stronger.

This inward gravity causes immense pressure within the stars and the greater the mass of a star, the bigger effect it has on gravity and pressure, resulting in more nuclear fusion.

In Summary

Stars don’t require oxygen to burn and, although there may be small residual amounts leftover from fusing hydrogen atoms, stars don’t have any oxygen to burn especially any that is used in nuclear fusion.

Instead of using carbon-based combustion, stars use nuclear fusion, and therefore, no oxygen is used in the burning process.