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ASTR 1102-002 2008 Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture08]
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Chapter 16: Our Star, the Sun
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Chapter Overview The Sun’s Interior –16-1: The source of the Sun’s heat and light –16-2: How scientists model the Sun’s internal structure –16-3: How the Sun’s vibrations reveal what lies beneath its glowing surface –16-4: How scientists are able to probe the Sun’s energy-generating core This is the textbook material on which I will focus.
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Sun’s Internal Structure Figure 16-4
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Modeling the Sun’s Interior 1.Hydrostatic Equilibrium 2.Thermal Equilibrium 3.Energy from nuclear fusion (E = mc 2 )
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Modeling the Sun’s Interior Hydrostatic Equilibrium –Gas pressure force (directed outward) balances force of gravity (directed inward) throughout the interior –If not balanced, Sun’s structure should change appreciably in a matter of hours!
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Modeling the Sun’s Interior Hydrostatic Equilibrium –Gas pressure force (directed outward) balances force of gravity (directed inward) throughout the interior –If not balanced, Sun’s structure should change appreciably in a matter of hours!
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Modeling the Sun’s Interior Thermal Equilibrium –Sun is steadily losing energy at its surface (it’s shining!); it is trying to “cool off” –Heat from the Sun’s interior slowly diffuses toward the surface –This lost heat can be replenished by slow gravitational contraction (whenever a gas is compressed, its temperature rises); this is referred to as “Kelvin-Helmholtz contraction” ( see §16-1 ) –If Kelvin-Helmholtz contraction is responsible for keeping the Sun’s interior hot, the Sun’s structure should change appreciably on a time scale of ~ 10 million years
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Modeling the Sun’s Interior Thermal Equilibrium –Sun is steadily losing energy at its surface (it’s shining!); it is trying to “cool off” –Heat from the Sun’s interior slowly diffuses toward the surface –This lost heat can be replenished by slow gravitational contraction (whenever a gas is compressed, its temperature rises); this is referred to as “Kelvin-Helmholtz contraction” ( see §16-1 ) –If Kelvin-Helmholtz contraction is responsible for keeping the Sun’s interior hot, the Sun’s structure should change appreciably on a time scale of ~ 10 million years
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Modeling the Sun’s Interior Thermal Equilibrium –Sun is steadily losing energy at its surface (it’s shining!); it is trying to “cool off” –Heat from the Sun’s interior slowly diffuses toward the surface Radiative diffusion (diffusion of light) Convection (“boiling”) Timescale: It takes approximately 170,000 years for energy created at the Sun’s center to travel to and escape from the surface of the Sun!
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Modeling the Sun’s Interior Thermal Equilibrium –Sun is steadily losing energy at its surface (it’s shining!); it is trying to “cool off” –Heat from the Sun’s interior slowly diffuses toward the surface –This lost heat can be replenished by slow gravitational contraction (whenever a gas is compressed, its temperature rises); this is referred to as “Kelvin-Helmholtz contraction” ( see §16-1 ) –If Kelvin-Helmholtz contraction is responsible for keeping the Sun’s interior hot, the Sun’s structure should change appreciably on a time scale of ~ 10 million years
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Modeling the Sun’s Interior Thermal Equilibrium –Sun is steadily losing energy at its surface (it’s shining!); it is trying to “cool off” –Heat from the Sun’s interior slowly diffuses toward the surface –This lost heat can be replenished by slow gravitational contraction (whenever a gas is compressed, its temperature rises); this is referred to as “Kelvin-Helmholtz contraction” ( see §16-1 ) –If Kelvin-Helmholtz contraction is responsible for keeping the Sun’s interior hot, the Sun’s structure should change appreciably on a time scale of ~ 10 million years
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A Problem with Time Scales!
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Chemical Elements & Their Isotopes Courtesy of: http://atom.kaeri.re.kr/ http://atom.kaeri.re.kr/
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Chemical Elements & Their Isotopes Hydrogen
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Chemical Elements & Their Isotopes Hydrogen
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Chemical Elements & Their Isotopes Helium
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Chemical Elements & Their Isotopes Helium
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Chemical Elements & Their Isotopes Carbon
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Chemical Elements & Their Isotopes Carbon
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Chart of Nuclides
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C 14
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Chart of Nuclides C 14 6 + 8 = 14
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