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Heavy Elements.pptx
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- 2. Prayer Heavenly Father Grant meeach day the desire to do my best, To grow mentally and morally as well as physically, To be kind and helpful to my classmates and teachers, To be honest with myself as well as with others, Help me to be a good sport and smile when I lose as well as when I win, Teach me the value of true friendship Help me always to conduct myself so as to bring credit to my school. Amen
- 3. Give evidence forand describe the formation of heavier elements during star formation and evolution.S11/12PS-IIIa-1 Objective:
- 4. Specific Objective: Explain stellarnucleosynthesis; Describe the different stages of life cycle of stars; Cite the different heavy elements formed in each stages of Star Cycle;
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- 6. STELLAR NUCLEOSYNTHESIS Process bywhich elements are formed within the stars as a result of nuclear fusion. NUCLEAR FUSION Process by which multiple nuclei joined together to form a heavier nucleus.
- 7. Stars are formedwhen gravity started acting on matter and particles expanding with the universe. Dense region of molecular clouds, known as stellar nurseries (interstellar matter) collapse to form young stellar objects known as stellar PROTOSTARS which eventually become mature stars. Stellar Evolution – is a process by which a star changes during its lifetime. STAR FORMATION
- 8. All starsare born from clouds of gas called nebulae or molecular clouds that collapsed due to gravity. As the cloud collapses, it breaks into smaller fragments which contract to form a superhot stellar core called PROTOSTAR.
- 9. The protostarcontinues to accumulate gas and dust from the molecular cloud, and continues to contract while the temperature increases. Hydrogen will start combining with one another when the temperature reached 10,000 K in a series of proton-proton fusion reactions. These nuclear reactions release positrons and neutrinons which increase pressure and stop the contractions.
- 10. When thecontraction stops, the gravitational equilibrium is reached, and the protostar has become the MAIN SEQUENCE STAR.
- 11. 1. PROTON-PROTON CHAIN Deuterium /Deuteron Protium/ Proton Helium– 3 2 1 1 1 3 2 Helium – 3 Helium – 3 Helium – 4
- 12. A starspend most of its lifetime at this stage. Star condition during this period is referred to as stable main sequence star. Hot stars at this phase are luminous blue, while cool stars are faint red. The sun being intermediate in temperature, gives a yellow color. A yellow star remains a main sequence star for about 10 billion years.
- 13. 2. Carbon FusionCycle or CNO Cycle ᵧ Gamma Ray 𝑽 Neutrino Proton Neutron Positron ⁴He ¹He ¹He ᵧ ᵧ ᵧ 𝑽 C 𝑽 C N 13 12 13 N N 15 14 15 1 H O H 1
- 14. The proton-protonchain reactions will exhaust all hydrogen in the core of a main sequence star. Hydrogen fusion becomes significant on the outer shell, while some of it is also fused to the core`s surface. When most of the hydrogen in the core is fused into helium, fusion stops and the pressure in the core decreases. Helium is converted to carbon in the core via alpha processes, increasing the star`s core density and temperature and subsequently creating a RED GIANT.
- 15. The rateof alpha fusion processes decreases as carbon is formed in the core. Gravity again squeezes the star. The stars fuel is depleted and over time the outer material of the star is blown off into space as planetary nebula. The only thing that remains is the hot and inert carbon. The star becomes a white dwarf.
- 16. Life Cycle ofa Star Stellar Nebula Average Star Red Giant Planetary Nebula White Dwarf Proto star Main Sequence Star
- 17. The stargoes through a series of stages where heavier elements are fused in the core and the shells around the core. The element oxygen is formed from carbon fusion; neon from oxygen fusion, silicon from neon fusion; and iron from silicon fusion. The stars become a multiple-shell red-giant
- 18. 3. Alpha Ladder Asthe fusion of elements with ⁴He continues, heavier elements are created all the way to IRON. This makes the sun more massive.
- 19. When thecore can no longer produce energy to resist gravity, the star is doomed. Gravity squeezes the core until the star explodes and releases a large amount of energy. The star explosion is called a supernova. The explosion also releases massive amount of high energy neutrinos which, in turn, breaks nucleons and release neutrons. These neutrons are picked up by nearby stars and lead the creation of elements heavier than Iron.
- 20. Elements heavier thanIron are formed during supernova explosion Supernova releases tremendous amount of energy enough to synthesize elements heavier than Iron
- 21. After supernovaexplosion, it is believed that a NEUTRON STAR is formed. Which is also known as the smallest star. Black hole is a region in space where gravity is too strong that no matter can escape from it.
- 22. Life Cycle ofa Star Stellar Nebula Neutron Star Supernova Red Supergiant Massive Star Black Hole Proto star Main Sequence Star
- 23. As the energyat the core of the stars decreases, nuclear fusion cannot produce elements higher than Iron, Because fusion reaction becomes unfavorable. This is because the NUCLEAR BINDING ENERGY PER NUCLEON, the energy that holds the nucleus intact, decreases after Iron. Therefore, different pathways is needed for heavier elements to be formed.
- 24. Life Cycle of aStar Stellar Nebula Average Star Red Giant Planetary Nebula White Dwarf Neutron Star Supernova Red Supergiant Massive Star Black Hole Proto star Main Sequence Star
- 25. Synthesis of heavierelements happens via NEUTRON CAPTURE Neutron capture, a neutron is added to a seed nucleus. The addition of neutron produces a heavier isotope of the elements. Neutron capture can be slow or rapid.
- 26. Synthesis of heavierelements happens via NEUTRON CAPTURE Neutron capture can be slow or rapid. S process or slow process happen when there is slow rate of capturing neutron while there is faster rate of radioactive decay hence increasing the proton by 1.
- 27. Synthesis of heavierelements happens via NEUTRON CAPTURE Neutron capture can be slow or rapid. R process means that there is a faster rate of capturing neutron before it undergoes radioactive decay, thus more neutron can be combined at the nucleus. This is what happens in a supernova forming heavier elements than Iron with the process known as supernova nucleosynthesis.
- 28. Activity 3. Fillin the diagram with the correct term used during the stages of star formation where heavy elements are formed. Direction: Fill in the diagram with the correct term used during the stages of star formation where heavy elements are formed.