Nuclear fusion in the sun

What you need:

• Basic knowledge of physics

Nuclear fusion in the sun - this is how energy is created

• energy from atomic particles, light nuclei can be obtained not only through nuclear fission of heavy elements, but also through fusion (technically: nuclear fusion or just fusion).
• So not only the sun, but all stars get their energy from the fusion of hydrogen nuclei. This creates the heavier element helium and energy in the form of moving neutrons and gamma radiation.
• In other words: the sun and stars get their energy from converting hydrogen into helium. This process takes place at high temperatures in the central core of the star.

The CNO cycle - a complicated chain

Although this CNO cycle (also called carbon cycle) is a complicated chain of reactions it was known much earlier than the (much simpler) hydrogen chain (also known as the proton-proton chain called).

• This first cycle, in which the atoms carbon, nitrogen and oxygen (hence CNO) form a kind of protective building in which in the course of the process The reaction from hydrogen atoms to form helium atoms was developed in 1938 by the two physicists Hans Bethe and Carl Friedrich von Weizsäcker discovered.


Why is the sun burning? - Nuclear fusion simply explained

Even if you thought that earlier: Nothing burns in the sun. The recipe for ...

• The process is actually complicated and assumes that there are other elements in the star in addition to hydrogen as fuel, such as e.g. B. Carbon there.
• The carbon (C-12) plays the role of a catalyst in nuclear fusion.
• Hydrogen accumulates on these atoms when they collide; a nucleus of the element nitrogen (N-13) is created.
• This nitrogen is radioactively converted into a heavier carbon isotope (C-13).
• If another hydrogen atom hits this nucleus, nitrogen is produced again, but a heavier isotope (N-14).
• The cycle continues when it hits another hydrogen atom, creating an isotope of oxygen (O-15).
• However, this isotope is radioactive, it breaks down to N-15, a nitrogen isotope.
• As a result of these fusion processes, the C-12 has now become a heavy N-15.
• If another hydrogen atom hits this heavier core particle, it does not form an even heavier atomic nucleus, instead it becomes a helium atom (2 hydrogen atoms, 2 neutrons) repelled. The core is transformed back into the old carbon core (C-12). The cycle or the cycle reaction is thus closed.
• During this process, a total of four hydrogen atoms were "swallowed" and a helium nucleus was formed.
• However, only Bethe received the Nobel Prize in 1967 for discovering this nuclear fusion process.
• It quickly became clear: There had to be a simpler process for nuclear fusion, because the first stars did not yet have any carbon for this cycle.