Charles Hakes Fort Lewis College 1

Solar Interior/ Nuclear Fusion Charles Hakes Fort Lewis College 2

Outline Solar interior Fusion Solar evolution Stars Charles Hakes Fort Lewis College 3

Tutoring Wednesday 4:30-6:00 Berndt 640 USE IT OR LOSE IT Charles Hakes Fort Lewis College 4

Review Sunspots… are darker because they are actually cooler than the rest of the Sun the result of a “kink” in the magnetic field size of Earth; usually come in pairs magnetic field switches every 11 year; cycle is 22 years Maunder minimum corresponded to mini ice age Charles Hakes Fort Lewis College 5

Review and… The solar equator rotates faster than the poles the Zeeman effect is a splitting of spectral lines from magnetic fields sunspots magnetic field is about 1000x greater than the surrounding area solar wind is the sun evaporating Charles Hakes Fort Lewis College 6

As the Sun rotates, an individual sunspot can be tracked across its face. From Eastern to Western limb, this takes about: A) 12 hours B) A week C) Two weeks D) A month E) 5.5 years Charles Hakes Fort Lewis College 7

As the Sun rotates, an individual sunspot can be tracked across its face. From Eastern to Western limb, this takes about: A) 12 hours B) A week C) Two weeks D) A month E) 5.5 years Charles Hakes Fort Lewis College 8

Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater Charles Hakes Fort Lewis College 9

Compared to the Earth, the Sun’s average density is: A) lower B) about the same C) much greater Charles Hakes Fort Lewis College 10

From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation Charles Hakes Fort Lewis College 11

Solar Atmosphere Photosphere - Chromosphere - Transition zone/Corona - What we see. (~5780 K) Chromosphere - pinkish color (from Ha line); can see during eclipse. cooler temperature (~4500 K) Transition zone/Corona - Shift from absorption spectrum to emission spectrum Corona very hot (~3 million K) Solar Wind - The Sun is evaporating! Charles Hakes Fort Lewis College 12

Figure 9.10 Solar Chromosphere Charles Hakes Fort Lewis College 13

Figure 9.12 Solar Corona Charles Hakes Fort Lewis College 14

Figure 9.24 Active Corona Charles Hakes Fort Lewis College 15

Figure 9.13 Solar Atmospheric Temperature Charles Hakes Fort Lewis College 16

What about the internal structure? Charles Hakes Fort Lewis College 17

Solar Composition Element Number Percent Mass Percent H 91.2 71 He 8.7 27.1 O 0.078 0.97 C 0.043 0.4 N 0.0088 0.096 Charles Hakes Fort Lewis College 18

Figure 9.2 Solar Structure Charles Hakes Fort Lewis College 19

Internal Structure Core - Radiation Zone - Convection Zone - temperatures hot enough for nuclear reactions (~15 million K) Radiation Zone - Temperatures cooler, so no nuclear reactions. Hot enough so everything is ionized. Atoms can’t absorb photons. Convection Zone - Temperature cooler. Atoms form and can absorb radiation. Charles Hakes Fort Lewis College 20

Figure 9.6 Solar Interior Charles Hakes Fort Lewis College 21

How do we know what is inside the Sun? Charles Hakes Fort Lewis College 22

How do we know what is inside the Sun? Standard model Charles Hakes Fort Lewis College 23

Figure 9.4 Stellar Balance Charles Hakes Fort Lewis College 24

Figure 9.5 Solar Oscillations Charles Hakes Fort Lewis College 25

Figure 9.7 Solar Convection Charles Hakes Fort Lewis College 26

Figure 9.8 Solar Granulation Charles Hakes Fort Lewis College 27

possibly related to seismic activity Figure 9.11 Solar Spicules dynamic jets 5-10 minute life possibly related to seismic activity Charles Hakes Fort Lewis College 28

Typically, a granule in the photosphere of the sun is about the size of? A) A city, ~20-30 kilometers across. B) Texas, ~1000 km across. C) The Earth, ~12,000 km across. D) Jupiter, ~100,000 km across. Charles Hakes Fort Lewis College 29

Typically, a granule in the photosphere of the sun is about the size of? A) A city, ~20-30 kilometers across. B) Texas, ~1000 km across. C) The Earth, ~12,000 km across. D) Jupiter, ~100,000 km across. Charles Hakes Fort Lewis College 30

From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation Charles Hakes Fort Lewis College 31

From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation Charles Hakes Fort Lewis College 32

Misc notes Problem 9.1 Should say “Section 9.1” and NOT 16.1. And note that Mercury’s orbit is very eccentric, so you can’t simply use the semi-major axis for it’s distance at perihelion. Charles Hakes Fort Lewis College 33

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Nuclear Fusion Charles Hakes Fort Lewis College 35

Forces in Nature Gravity - long range; relatively weak. Electromagnetic - long range; responsible for atomic interactions (chemistry) Weak Nuclear Force - short range; responsible for some radioactive decay Strong Force - short range; holds nuclei together Charles Hakes Fort Lewis College 36

nucleus 1 + nucleus 2 = nucleus 3 + energy Nuclear Fusion Combining light nuclei into heavy ones. nucleus 1 + nucleus 2 = nucleus 3 + energy Law of conservation of mass and energy E = mc2 Charles Hakes Fort Lewis College 37

Figure 9.25 Proton Interactions Like charges (two protons) repel by electromagnetic force. With enough energy (temperature) and pressure, can overcome EM force Charles Hakes Fort Lewis College 38

4 protons ==>> helium-4 + 2 neutrinos + energy Proton-Proton chain Most common reaction in the Sun. 4 protons ==>> helium-4 + 2 neutrinos + energy Many other reactions are possible, but 90% are the proton-proton chain. Calculate energy produced from mass differences. (use E=mc2), get 4.3x10-12 J (Joules) when 4 protons fuse to Helium. From Sun’s luminosity, can calculate that 600 million tons of Hydrogen per second are fused into Helium. Charles Hakes Fort Lewis College 39

Figure 9.26 Solar Fusion Charles Hakes Fort Lewis College 40

Proton-Proton chain Neutrinos - “little neutral one” are almost mass-less, and react with almost nothing. Charles Hakes Fort Lewis College 41

Figure 9.27 Neutrino Telescope - Super Kamiokande Need large amounts of matter to detect neutrinos Solar Neutrino Problem - until recently could not explain observed low numbers. Charles Hakes Fort Lewis College 42

Proton-Proton chain Neutrinos “oscillations” explain the observation discrepancy. Neutrinos take eight minutes to get to the Earth from the Sun. In that time they can mutate (oscillate) into other forms. Charles Hakes Fort Lewis College 43

Three Minute Paper Write 1-3 sentences. What was the most important thing you learned today? What questions do you still have about today’s topics? Charles Hakes Fort Lewis College 44