When it becomes a red giant, how luminous will the Sun be? A) 0.001 L solar B) 1 L solar C)1000 L solar Quiz Question: Red Giants
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When it becomes a red giant, how luminous will the Sun be?
A)0.001 LsolarB)1 LsolarC)1000 Lsolar
Quiz Question: Red Giants
When it becomes a red giant, how luminous will the Sun be?
A)0.001 LsolarB)1 LsolarC)1000 Lsolar
Quiz 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 Questions
Fig.
17.
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In 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 Cycle
Fig.
17.
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He 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 Capture
Why 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 Question
Why 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 Question
Fig.
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High 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 Stars
Fig.
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•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 Stars
In which state does the ball have less energy?
Ground floor of Duane
Second floor of Duane
A)State AB)State B
State A
State B
Concept Question—Preparation for Why Fusion
Stops at Fe
In which state does the ball have less energy?
Ground floor of Duane
Second floor of Duane
A)State AB)State B
State A
State B
Concept Question—Preparation for Why Fusion Stops at Fe
Nature tends toward the lowest energy state.
Ene
rgy
Position
Assuming 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 Fe
Fig.
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Fe 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 Fe
Fig. 17.22
The Cosmic Abundance of Elements
Fig. 17.25High Mass Stars Low Mass Stars
The Big Picture of Stellar Evolution
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