Nuclear Fusion Reactions in Stars PDF

Lesson 1.2 The Nuclear Fusion Reactions in Stars Objective At the end write the nuclear of the 1 fusion reactions that lesson, you take place in stars. should be able to:  Learn about It! Stellar Nucleosynthesis Stellar nucleosynthesis refers to the set of nuclear fusion...

Lesson 1.2 The Nuclear Fusion Reactions in Stars Objective At the end write the nuclear of the 1 fusion reactions that lesson, you take place in stars. should be able to:  Learn about It! Stellar Nucleosynthesis Stellar nucleosynthesis refers to the set of nuclear fusion reactions in a star's core and overlying layers Responsible for the formation of elements heavier than those formed during big bang nucleosynthesis (H, He, Li and Be)  Learn about It! Stellar Nucleosynthesis Theory Arthur Eddington Used atomic mass measurements of F. W. Aston Stars get energy from the nuclear fusion of H nuclei Heavier elements are formed inside stars  Learn about It! Stellar Nucleosynthesis Theory George Gamow Derived the formula for mutual electrostatic repulsion Refers to the probability of bringing two nuclei close enough such that their forces overcome the Coulomb barrier Derived the rate at which high-temperature reactions occur  Learn about It! Stellar Nucleosynthesis Theory Hans Bethe Elucidated how energy is produced in stars via hydrogen burning  Learn about It! Hydrogen Burning Hydrogen burning refers to a set of stellar reactions resulting in the production of He-4 from H Responsible for producing energy in stars Two dominant processes Proton-proton chain reaction (responsible for the formation of helium cores) Carbon-nitrogen-oxygen (CNO) cycle  Learn about It! Hydrogen Burning Proton-proton chain reaction Chain reaction by which a star transforms H into He Occurs only when there is mutual electrostatic repulsion  Learn about It! Hydrogen Burning Proton-proton chain reaction 1.Beta-plus decay: two ps fuse to form a deuteron (deuterium nucleus) a positron (a positively-charged electron) a neutrino 2.Deuterium burning: D fuses with p to yield He-3 and γ 3. Fusion of two He-3 to form He-4  Learn about It! Hydrogen Burning Carbon-nitrogen-oxygen cycle 1.Proton capture: 12C fuses with p to form 13N and γ 2.Beta-plus decay: 13N producing 13 C, a positron and a neutrino 3. Fusion of 13C with p to yield 14N and γ  Learn about It! Hydrogen Burning Carbon-nitrogen-oxygen cycle 4.Proton capture: 14N fuses with p to form 15O and γ 5.Beta-plus decay: 15O producing 15 N, a positron and a neutrino 6. Fusion of 15N with p to yield 12C and 4 He  Learn about It! Helium Burning Helium burning refers to a set of stellar nuclear reactions that uses helium to produce energy and heavier elements such as Be, O, Ne and Fe Also responsible for producing energy in stars Two dominant processes Triple-alpha process Alpha process  Learn about It! Helium Burning Triple-alpha process Set of two-stage nuclear fusion reactions converting three alpha particles (He-4 nuclei) into 12C Creates inert carbon core found in white dwarfs and larger stars  Learn about It! Helium Burning Triple-alpha process 1. Two alpha particles fuse to yield 8 Be and γ 2. 8Be fuses with another alpha particle to form 12C and γ  Learn about It! Helium Burning Alpha processes Set of nuclear reactions that convert He into heavier elements The reactions consume He and ultimately ends at Fe 56Fe is the most stable element, having the lowest mass to nucleon (mass number) ratio  Learn about It! Helium Burning Alpha processes 1. Increases the core size and density by forming heavier elements 2. Vital in transforming main sequence stars to supergiants  Learn about It! Helium Burning Alpha processes 3. Reactions capture an alpha particle and release a γ 12C captures an alpha particle (4He) to make 16O, then 16O captures an alpha particle to produce 20Ne  Learn about It! Helium Burning Alpha processes 4. The process continues where the product captures an extra alpha particle until it produces the last atom in the series (52Fe) 5. All atoms produced are from even- numbered elements Key Points Stellar nucleosynthesis is the process by which 1 elements are formed in the cores and overlying layers of the stars through nuclear fusion reactions. Hydrogen burning is a set of stellar processes that 2 produce energy in the stars. Helium burning is a set of stellar nuclear reactions 3 that uses helium to produce heavier elements such as beryllium, oxygen, neon and iron.  Check Your Understanding Provide the products of the following nuclear reactions.  Challenge Yourself How is 12 C formed via the triple-alpha process?  Bibliography Clayton, D.D. 1968. Principles of Stellar Evolution and Nucleosynthesis. Chicago, USA: University of Chicago Press. Constan, Z. “Learn Nuclear Science with Marbles.” National Science Foundation 2017. Accessed July 13, 2018. http://www.jinaweb.org/outreach/marble/Marble%20Nuclei %20Project%20-%20Activities%20Student%20Worksheet.pdf Langer, N. “Nucleosynthesis.” Bonn University SS 2012. Accessed December 8, 2016. https:// astro.uni-bonn.de/~nlanger/siu_web/nucscript/Nucleo.pdf Overton, Tina, et al. 2010. Shriver and Atkins’ Inorganic Chemistry. 5th ed. London: Oxford University Press.