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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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Presentation on theme: "ASTR 1102-002 2008 Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture08]"— Presentation transcript:

1 ASTR Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture08]

2 Chapter 16: Our Star, the Sun

3 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.

4 Sun’s Internal Structure Figure 16-4

5 Modeling the Sun’s Interior 1.Hydrostatic Equilibrium 2.Thermal Equilibrium 3.Energy from nuclear fusion (E = mc 2 )

6 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!

7 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!

8 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

9 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

10 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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15 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

16 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

17 A Problem with Time Scales!

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20 Chemical Elements & Their Isotopes Courtesy of:

21 Chemical Elements & Their Isotopes Hydrogen

22 Chemical Elements & Their Isotopes Hydrogen

23 Chemical Elements & Their Isotopes Helium

24 Chemical Elements & Their Isotopes Helium

25 Chemical Elements & Their Isotopes Carbon

26 Chemical Elements & Their Isotopes Carbon

27 Chart of Nuclides

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34 C 14

35 Chart of Nuclides C = 14

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