Energy is generated in the sun and other stars by fusion One of the fusion cycles, the protonproton cycle, consists of the following reactions 1 H 1 H 2 H v e 1 H 2 H 3 He Followed by 1 H 3 H 4 H v e (a) Show that the net effect of these reactions is 4 1 H 4 He 2 2v e (b) Show that rest energy of 2...

a Sum of the three reactions 4 1 H 2 H 3 He 2 H 3 He 4 He 2 ...

Energy is generated in the sun and other stars by fusion. One of the fusion cycles, the

Question:

Energy is generated in the sun and other stars by fusion. One of the fusion cycles, the proton–proton cycle, consists of the following reactions:

¹H + ¹H → ²H + β⁺ + v_e

¹H + ²H → ³He + γ

Followed by

¹H + ³H → ⁴H + β⁺ + v_e

(a) Show that the net effect of these reactions is

4¹H → ⁴He + 2β⁺ + 2v_e + γ

(b) Show that rest energy of 24.7 MeV is released in this cycle (not counting the energy of 1.02 MeV released when each positron meets an electron and the two annihilate).

(c) The sun radiates energy at the rate of about 4 × 10²⁶ W. Assuming this is due to the conversion of four protons into helium plus γ rays and neutrinos, which releases 26.7 MeV, what is the rate of proton consumption in the sun? How long will the sun last if it continues to radiate at its present level?