ch14 astro2_lecppt_ch14_schultz

ch14 astro2_lecppt_ch14_schultz - Chapter14 LectureOutline...

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Chapter 14 Lecture Outline A Run-of-the-Mill G Dwarf: Our Sun
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  21st CENTURY ASTRONOMY, 2/e 2 Structure of the Sun  We only see the outer layers of the Sun. Physics tells us about the interior. Key idea: hydrostatic equilibrium. At each point there’s a balance: Outward pressure = inward force of gravity. Rate of energy emitted = rate produced in the core. Density, temperature, pressure increase towards the center.
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  21st CENTURY ASTRONOMY, 2/e 3 A Solar Model
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  21st CENTURY ASTRONOMY, 2/e 4 Powering the Sun The Sun has been around a long time: about 4.6 billion years. The Sun must therefore generate a lot of energy over a long time. Source: fusion (joining) of hydrogen to helium in the central core. Fusion is often called hydrogen burning . This happens for all main sequence stars.
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  21st CENTURY ASTRONOMY, 2/e 5 Fusion and Energy Mass of He nucleus is smaller than that of original four H nuclei. Difference in mass is called the mass deficit . Relativity: mass and energy are equivalent: E = mc 2 or m = E / c 2 Mass of He is smaller because binding energy is released during fusion. Binding energy = (mass deficit) × c 2 .
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  21st CENTURY ASTRONOMY, 2/e 6 Atomic Nuclei Nuclei consist of protons and neutrons. Protons: positive electrical charge. Neutrons: no electrical charge. Electrical forces push protons apart. The strong nuclear force binds protons together. Fusion requires ramming protons together at high speed (i.e., at high temperature).
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  21st CENTURY ASTRONOMY, 2/e 7 Isotopes of Hydrogen and Helium Number of protons sets the type of atom. Isotopes:
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ch14 astro2_lecppt_ch14_schultz - Chapter14 LectureOutline...

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