ASTR 1102 002 2008 Fall Semester Joel E Tohline Alumni Professor Office 247 Nicholson Hall Slides from Lecture08 Chapter 16 Our Star the Sun 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 Figure 16 4 Sun s Internal Structure Modeling the Sun s Interior 1 Hydrostatic Equilibrium 2 Thermal Equilibrium 3 Energy from nuclear fusion E mc 2 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 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 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 KelvinHelmholtz 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 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 KelvinHelmholtz 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 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 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 KelvinHelmholtz 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 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 KelvinHelmholtz 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 A Problem with Time Scales Chemical Elements Their Isotopes Courtesy of http atom kaeri re kr Chemical Elements Their Isotopes Hydrogen Chemical Elements Their Isotopes Hydrogen Chemical Elements Their Isotopes Helium Chemical Elements Their Isotopes Helium Chemical Elements Their Isotopes Carbon Chemical Elements Their Isotopes Carbon Chart of Nuclides Chart of Nuclides Chart of Nuclides Chart of Nuclides Chart of Nuclides Chart of Nuclides Chart of Nuclides Chart of Nuclides 14 C Chart of Nuclides 14 6 8 14 C