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Notes on Proton-Proton Fusion in the Sun's Core, Exams of Physics

University of Dallas (UD)Physics

These lecture notes detail the process of proton-proton fusion in the core of the sun, including the temperature and conditions required for fusion, the steps in the fusion reaction, and the conversion of mass into energy according to einstein's famous equation.

Typology: Exams

2021/2022

Uploaded on 09/27/2022

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Ast 4 Lecture 12 Notes

1 Fusion in the core

Inside the core

•Temperature ∼1.5×107K

•Hydrogen and Helium in the form of plasma

•Plasma: positively charged ions and free electrons

•Due to the high temperatures electrons are no longer attached to nuclei

•Positively charged nuclei moving at high

speeds

•Like charges repel

•The closer nuclei come together →

stronger the repulsive force

•If the distance between nuclei <10−15m,

the strong nuclear force overpowers the

electromagnetic repulsion

•temperature and pressure in core allow fu-

sion of hydrogen nuclei

2 Proton-proton chain

2.1 Step 1

Step 1

•Two protons fuse to form a deuteron re-

leasing a positron and neutrino

•A deuteron is a nucleus of a isotope of hy-

drogen called deuterium (2H)

•A deuteron consists of a proton and a neu-

tron

•1H + 1H→2H + e++ν+ energy

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Ast 4 Lecture 12 Notes

1 Fusion in the core

Inside the core

Temperature ∼ 1. 5 × 107 K
Hydrogen and Helium in the form of plasma
Plasma: positively charged ions and free electrons
Due to the high temperatures electrons are no longer attached to nuclei
- Positively charged nuclei moving at high speeds
- Like charges repel
- The closer nuclei come together → stronger the repulsive force
- If the distance between nuclei < 10 −^15 m, the strong nuclear force overpowers the electromagnetic repulsion
- temperature and pressure in core allow fu- sion of hydrogen nuclei

2 Proton-proton chain

2.1 Step 1

Step 1

Two protons fuse to form a deuteron re- leasing a positron and neutrino
A deuteron is a nucleus of a isotope of hy- drogen called deuterium (^2 H)
A deuteron consists of a proton and a neu- tron
1 H + 1 H → 2 H + e+^ + ν + energy

Step 1

A positron is the antiparticle of an elec- tron
identical to electron except has a positive charge
when a positron and an electron meet they annihilate each other producing gamma ray photons
e+^ + e−^ → 2 γ

2.2 Step 2

Step 2

A proton interacts and fuses with a deuteron producing a helium-3 (^3 He) nu- cleus
Energy is emitted in the form of a gamma- ray photon
1 H + 2 H → 3 He + γ + energy

2.3 Step 3

Step 3

Final step is the production of helium- nuclei
two helium-3 nuclei fuse to form one helium-4 nucleus plus two protons
3 He + 3 He → 4 He + 1 H + 1 H + energy

2.4 Total Reaction

Total reaction

4 1 H → 4 He + 2 e+^ + 2 ν + 2 γ + energy
Where did the energy come from?

Hydrostatic equilibrium Hydrostatic equilibrium keeps the fusion process at a constant rate (like a thermostat)

Scenario 1:

If the fusion process where to speed up → more energy would be produced and pressure would increase
This added pressure would cause the core to expand and cool, and the fusion rate would slow down to normal

Hydrostatic equilibrium Hydrostatic equilibrium keeps the fusion process at a constant rate (like a thermostat)

Scenario 2:

If the core temperature were to drop → decrease in fusion rate
The pressure would decrease and the core would contract
As the core shrank → temperature would increase → fusion rate would return to normal

Hydrostatic equilibrium

Energy produced by fusion travels toward the surface at a steady rate
The amount of energy leaving the top of a gas layer is equal to the energy entering the bottom

Notes on Proton-Proton Fusion in the Sun's Core, Exams of Physics

Related documents

Partial preview of the text

Download Notes on Proton-Proton Fusion in the Sun's Core and more Exams Physics in PDF only on Docsity!

1 Fusion in the core

2 Proton-proton chain

2.1 Step 1

2.2 Step 2

2.3 Step 3

2.4 Total Reaction