When it becomes a red giant, how luminous will the Sun be?A) 0.001 LsolarB) 1 LsolarC)1000 LsolarQuiz Question: Red GiantsWhen it becomes a red giant, how luminous will the Sun be?A) 0.001 LsolarB) 1 LsolarC)1000 LsolarQuiz Question: Red Giants• Where do the heavy elements lighter than Fe come from?• How do high mass stars evolve differently from low mass stars?Stellar Evolution QuestionsFig. 17.16In high mass (>8 Msolar) stars, H is converted into 4He through the CNO cycle, in which C is a catalyst.H Fusion in High Mass Stars: The CNO CycleFig. 17.16He capture occurs in high mass stars in the latter stages of evolution, creating elements up to Fe in the periodic table.This can happen only in high mass stars because the electric repulsion is strong for highly charged nuclei.Fusion in the Late Stages of High Mass Stars: 4He CaptureWhy doesn’t the CNO cycle fuse H into He in the Sun, instead of the Proton-Proton chain?A)Because there is no C in the Sun.B)Because the electric repulsion between C and H is too great for the atoms in the Sun to overcome because its core is too cool.C)Because the electric repulsion betwee C and H is too great for the atoms in the Sun to overcome because its core is too hot.Concept QuestionWhy doesn’t the CNO cycle fuse H into He in the Sun, instead of the Proton-Proton chain?A)Because there is no C in the Sun.B)Because the electric repulsion between C and H is too great for the atoms in the Sun to overcome because its core is too cool.C)Because the electric repulsion betwee C and H is too great for the atoms in the Sun to overcome because its core is too hot.Concept QuestionFig. 17.18High mass stars have consecutive shells of fusion in the last stages of their lives—although not as clearly delineated as in the diagram. Essentially all elements in the Universe heavier then He were made in post main-sequence evolution of high mass stars.Fusion in the Late Stages of High Mass StarsFig. 17.19•High mass stars move horizontally across the H-R diagram during their evolution, always maintaining high luminosities.•High mass stars evolve much more quickly than low mass stars.Evolution on the H-R Diagram for High Mass StarsIn which state does the ball have less energy?Ground floor of DuaneSecond floor of DuaneA) State AB) State BState AState BConcept Question—Preparation for Why Fusion Stops at FeIn which state does the ball have less energy?Ground floor of DuaneSecond floor of DuaneA) State AB)State BState AState BConcept Question—Preparation for Why Fusion Stops at FeNature tends toward the lowest energy state.EnergyPositionAssuming that there is some friction so that the ball does not oscillate, the ball will go to the lowest energy state.Why Fusion Stops at FeFig. 17.20Fe is the most stable element. Energy cannot be liberated from Fe nuclei by fusion, so it is a stopping point in heavy element formation in stars.E=mc2; Fe has the lowest energy per nuclear particle Why Fusion Stops at FeFig. 17.22The Cosmic Abundance of ElementsFig. 17.25High Mass Stars Low Mass StarsThe Big Picture of Stellar
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