The Proton-Proton Chain



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tarix18.04.2018
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#39169

Target:

  • I can describe how energy is produced in the core of the sun.

The Proton-Proton Chain
How do we turn hydrogen into helium and make energy?
The process is called the Proton-Proton (PP) Chain, and it operates inside the Sun and stars of similar mass.

Step 1: Smash two protons together to make deuterium

http://burro.cwru.edu/academics/astr221/starphys/pp1m.gif
http://burro.cwru.edu/academics/astr221/starphys/pp1.gif

positron: like an electron, but with positive charge
neutrino: very light, hard-to-detect particle
Step 2: A proton crashes into a deuterium nucleus, making helium-3

http://burro.cwru.edu/academics/astr221/starphys/pp2m.gif
http://burro.cwru.edu/academics/astr221/starphys/pp2.gif
gamma ray: very high energy photon

Do Steps 1 and 2 again, so that we have two helium-3 nuclei. Then (69% of the time):

Step 3: Mash two helium-3 nuclei together to make helium-4

http://burro.cwru.edu/academics/astr221/starphys/pp3m.gif
http://burro.cwru.edu/academics/astr221/starphys/pp3.gifActually this is the most common path to making helium in the Sun, but not the only one. After Step 2 is complete, other reactions can take place -- the PPII chain (31% of the time):

http://burro.cwru.edu/academics/astr221/starphys/ppii.gif

Or even the PPIII chain (rare, 0.3% of the time):



http://burro.cwru.edu/academics/astr221/starphys/ppiii.gif

So what did we do?
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

Draw a diagram to represent the proton-proton chain

Astronomy: Stars, Galaxies and Cosmology Page



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