Activity 3 NUCLEOSYNTHESIS
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Stellar nucleosynthesis and supernova nucleosynthesis produce heavier elements through nuclear fusion reactions. During the main sequence, hydrogen fuses in the proton-proton chain reaction or CNO cycle in stars. In red giant and supergiant stars, helium fuses through the triple-alpha process and alpha ladder. Supernova explosions produce very heavy elements through the rapid r-process. The slower s-process in massive stars also produces heavier elements than iron.
Activity 3 NUCLEOSYNTHESIS
- 1. ACTIVITY 3. STELLAR NUCLEOSYNTHESIS and SUPERNOVA NUCLEOSYNTHESIS I. Main Sequence Stars a. Proton-proton chain reaction b. CNO cycle II. Red giant stars/Supergiant stars a. triple-alpha process Questions: 1. Write the equation of the proton-proton reaction chain. Make sure that the equation is balanced (with equal number of protons and neutrons for both sides). Hint: Step 1: 1H + ____ ____ + e+ + v Step 2: ____ + 1H ___ + Step 3: 3He + ____ ___ + 1H + ___ 2. Why do you think this reaction is called proton-proton chain reaction? 3. How many protons were used to produce 4He? Step 1 Step 2 Step 3 4. Complete the reactions below. Refer to the diagram given on the left. 5. What is the product of this cycle? 6. Why is it called the CNO cycle? 7. Complete the equations below. Refer to the diagram on the left side. 4 He + 4 He → 8Be + He → C + γ 8. Why do you think it is called triple alpha process? Which atom is referred to as “triple”?
- 2. b. alpha ladder c. S-process and r-process Read the excerpt below: d. Complete the graphic organizer below to summarize stellar nucleosynthesis and supernova nucleosynthesis. Choose from the following words below: S-process proton-proton chain reaction R-process alpha ladder Red giant stars/supergiant stars main sequence stars CNO cycle supernova explosion 9. What are the other elements produced in this process aside from H, He and Be? Write these elements in their correct format. The s-process is a type of nuclear reaction, believed to take place inside massive stars, in which elements heavier than copper are formed by the slow ("s") absorption of neutrons by atomic nuclei. The capture of neutrons occurs on time scales that are long enough to enable unstable nuclei to decay via the emission of a beta particle before absorbing another neutron. This contrasts with the r-process that is thought to operate in supernovae. Prominent s-process elements include barium, zirconium, yttrium, and lanthanum. On the other hand, r-process involves rapid capture of neutrons by the atom. It is a set of reactions in nuclear astrophysics that are responsible for the creation (nucleosynthesis) of approximately half the atomic nuclei heavier than iron. This process is also responsible for supernova explosion. 10. What does “s” mean in the s-process? 11. What does “r” mean in the r-process? 12. What is the difference between s- process and r-process?
- 3. Questions: Give at least 3 examples of elements that are formed from 13 Big Bang nucleosynthesis 14. Stellar nucleosynthesis 15. Supernova nucloesynthesis