The Sun emits energy which originates from a nuclear fusionnuclear fusionnuclear fusion process. The fusion occurs deep inside the core of the Sun. Inside this core the temperature reaches more than 15000000 K. Every second, 600 million tons of hydrogenhydrogenhydrogen converts into heliumheliumhelium and enormous energy is released.
The specific type of fusion that occurs inside of the Sun is known as proton‑proton fusion.
Proton‑proton chain reaction
Definition: Proton‑proton chain reaction
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The process starts with collisions of protons. These protons are the nuclei of hydrogenhydrogenhydrogen. In a series of steps these protons turn into heliumheliumhelium. The mass of helium is less than the mass of colliding protons and according to the principle of mass‑energy equivalence in the fusion energy is released. The resulting energy is radiated out from the core of the Sun and distributes across the Solar SystemSolar SystemSolar System.
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Proton‑proton chainproton‑proton chainProton‑proton chain reaction occurs in several steps.
Two pairs of protons fuse and two deuterons are formed.
Each deuteron collides with an additional proton to form helium .
Two helium nuclei fuse to create a and two protons.
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In proton‑proton chain two neutrinos, two positrons and gamma rays are released.
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The reactions involved in the proton‑proton chainproton‑proton chainproton‑proton chain are following:
Task 1
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Calculate the energy released in the proton‑deuteron step of proton‑proton chain. The deuteron mass is 3,343583772 ∙ 10Indeks górny -27-27 kg and the mass of proton is 1,6726219 ∙ 10Indeks górny -27-27 kg. Use exact values of the speed of light c = 299792458 . The relationrelationrelation between electronovolt and joule is following: 1 eV = 1,6021766208 ∙ 10Indeks górny -19-19 J. Compare your result with the information you have already read.
Time of reaction
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The averageaverageaverage time required for the first step of proton‑proton chainproton‑proton chainproton‑proton chain is extremely long. A hydrogenhydrogenhydrogen nucleus needs on the average 10Indeks górny 99 years to undergo an interaction with another nucleus in order to initiate the chain. The next step is very short and in the averageaverageaverage lasts about 1 s. In the last steps of the cycle the heliumheliumhelium nuclei needs about 400 years to produce the final helium nuclei .
The rate of proton‑proton chain is very low but still enough to produce huge amount of energy due to the enormous number of hydrogen atoms in the core of the Sun.
Remember
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In the proton‑proton fusion in the Sun, known as proton‑proton chain, protons in a series of steps turn into heliumheliumhelium. In this fusion tremendous amounts of energy are released.
Exercises
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Exercise 1
Exercise 2
Write the fusion reaction in symbolic way:
Exercise 3
Explain in English how the energy in the Sun is produced.