Star Energy

  • April, 2021

Have you ever wonder about how stars generate the amount of this large energy that we can see billions of light-years away? or how our sun radiating constant energy for 5 billion years? In this blog, we are going to look into the internal process of energy generation in stars ...

What is star ?

Stars are gravitationally-confined thermonuclear-fusion reactors If we talk about Our SUN or Main sequence star - These stars are in the process of steadily fusing hydrogen to helium and energy transported from core to surface of star via radiative diffusion and/or convection. In layman terms it's process of converting hydrogen to helium.

This thermonuclear fusion has 2 important factor
  • The proton-proton (PP) chain
  • The CNO cycle

The proton-proton (PP) chain

Now let's look first what happens into PP chain
We essentially turned 4 protons into

  • 1 helium nucleus
  • 1 positron (this positron will bump into a electron and annihilate, creating a gamma ray\energy!).
  • 1 gamma ray (energy!)
  • 1 neutrino

P-P chain

Step 1: Smash two protons together to make deuterium
Step 2: A proton crashes into a deuterium nucleus, making helium-3
Do Steps 1 and 2 again, so that we have two helium-3 nuclei
Now after we have helium 3 nuclei these are 3 ways we can create Helium-4
  • Path 1 Mash two helium-3 nuclei together to make helium-4 (most common path sun takes )
  • Path 2 The PPII chain (31% of the time )
  • Path 3 The PPIII chain rare, 0.3% of the time

CNO cycle

Now let's Understand what is CNO cycle

For stars heavier than the sun,CNO (carbon-nitrogen-oxygen) cycle of nuclear fusion is the dominant source of energy generation. The cycle results in the fusion of four hydrogen nuclei (1H, protons) into a single helium nucleus (4He, alpha particle), which supplies energy to the star in accordance with Einstein’s equation. Ordinary carbon,12C, serves as a catalyst in this set of reactions and is regenerated. Only relatively low energy neutrinos are produced in this cycle.
In layman terms it is also process of converting H to He with using Carbon.

CNO is 6 steps process

  • A carbon-12 nucleus captures a proton and emits a gamma ray, producing nitrogen-13.
  • Nitrogen-13 is unstable and emits a beta particle, decaying to carbon-13.
  • Carbon-13 captures a proton and becomes nitrogen-14 via emission of a gamma-ray.
  • Nitrogen-14 captures another proton and becomes oxygen-15 by emitting a gamma-ray.
  • Oxygen-15 becomes nitrogen-15 via beta decay.
  • Nitrogen-15 captures a proton and produces a helium nucleus (alpha particle) and carbon-12, which is where the cycle started.
  • At end the carbon-12 nucleus used in the initial reaction is regenerated in the final one and hence acts as a catalyst for the whole cycle

I am pretty sure you get clear idea about how star create energy , Now this is most introductory process for any star in universe but you are aware about when star end its life it will blast out heavy elements (example - iron, magnesium) so how it's produce ?For that you go to my friend's blog article

Stellar Nucleosynthesis - Neon Burning "