The Sun is, in its most basic description, a huge spinning ball of hot gas. It is approximately 90% hydrogen, 10% helium, and .1% lithium, carbon, and other elements. Okay, so that's easy enough to understand. But where does such a huge mass of gas come from? How does it continue to produce energy, and why is it so darn hot?
We can find the answers to these questions by looking at the very center of the Sun, the core.
The Sun exists because of a process called fusion or the proton cycle. In the core of the Sun, the temperature is so hot that the atoms are constantly colliding and tearing apart the hydrogen atoms to form separate protons, neutrons and electrons. These are the parts that make up an atom. The "freeing" of these particles is what lets the proton cycle take place. There are three basic reactions in this process.
The Fusion of Protons to Form a Deuteron
Two protons collide in this reaction. In order for this to happen, one of the protons must decay into a neutron. This is because a deuteron consists of a proton and a neutron. The protons must also be very close to each other which is unlikely because protons are both positively charged, which means they are likely to repel each other. It's a good thing that there are SO many protons available in the core, or it would be difficult for this reaction to even take place! You can see how these reactions work below:
Proton becomes a neutron
Two protons make a deuteron
The Formation of the Helium-3 Isotope
In this reaction, the deuteron from the first reaction fuses with another proton to make a combination of two protons and one neutron. This forms the isotope of helium-3, which is a different form of the helium that we are used to. To make that helium, we need the third reaction.
The deuteron and a proton form the helium-3 isotope
Helium is formed!
Here we have to have two of the isotopes from the second reaction come together to form real helium, with two protons and two neutrons. In order for this reaction to take place, the first two must have each occurred twice. This is because two isotopes are required for helium to be fully formed.
Two helium isotopes form a helium atom
There is another set of reactions in the Sun called the CNO cycle because they involve carbon, nitrogen and oxygen. This cycle was thought to be the main source of the Sun's energy. Today we know that the proton cycle is the most important set of reactions for the Sun. Just shows you how much new discoveries can change things in science!
Now, you may be wondering exactly why all of this has any importance to the Sun and what it does. Well, the main thing to remember from this is that each time helium is formed, a release of energy takes place. It is through these reactions that the Sun gets its energy. And all of them take place in the core!
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The Sun Radiative zone Convective zone Photosphere Chromosphere Corona