Nearly three-quartersof this mass is hydrogen, the lightest element in the universe.Almost a quarter is helium, the second lightest element. Then there is a little oxygen, carbon, iron and a few others that can be neglected.
The immense mass of gas forms a sphere with a diameter of 1.4 million kilometers.Gravity compresses the gas with unimaginable power, creating special conditions inside the sun. Or as a well-known television astrophysicist always says: the mother of a star is gravity, the father is the pressure. The collapse of matter due to gravity creates heat. So much heat that the hydrogen gas inside the sun turns into plasma, namely about 15.6 million. Degree. Plasma is a type of fourth statein which the electrons detach from the atomic shells.Atoms without electrons, i.e. free atomic nuclei, are called ions. This is the prerequisite for collisions between atomic nuclei.
Even in a plasma in which the ions move very, much faster than atoms in a gas, collisions are extremely rare, not least because atomic nuclei are extremely small.After all, hydrogen nuclei consist only of a single proton. But also because a quantum effect is needed so that the two protons do not repel each other before they collide. The probability of two such protons colliding is 14 billion years in thesun.
But because of the large mass, i.e. the unimaginable abundance of atomic nuclei, the collisions occur relatively frequently.
And what happens?
The two collided protons merge into a deuterium atom, and when it collides again with a proton, a helium-3 atom is formed.The helium-3 atoms also collide again, eventually forming a helium-4 atom and 2 hydrogen atoms. (Everything is very simplified!) In this process, quite a lot of energy is released, about 26 mega-electronvolts.This is unimaginably little for us. But: In the sun, as many protons collide as are contained in 546 tonsof hydrogen.Per second. These collisions are the cause of the sun ‘fire’. The sun has a power output of 386 quadrillion watts per hour. By comparison, 545 trillion watts are produced in Germany everyyear.
The heat from the nuclear fusion maintains the heat and thus the pressure inside the sun.Pressure is the adversary of gravity. Without him, the sun would collapse under its own weight. The sun “fire” thus ensures not only that we get beautiful, uniform heat, but also that the sun can exist as a stable system at all.
But where does the energy that is released during nuclear fusion come from?
It comes from the masses.Mass and energy are equivalent. When three protons become a helium-3 core, the final product, the helium-3 core, is lighter than the sum of the initial masses, the three protons. This “disappeared” mass is released in the form of energy, according to the formula E = mc2. So the sun has its energy from the masses. It really “burns” a little of itself, in the sense that it becomes a little lighter and releases energy. But this is just a metaphor, since nuclear fusion is a completely different chemical/physical process than a fire as we know it from Earth.