Transcript No Slide Title

Charles Hakes
Fort Lewis College
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Solar Interior/
Nuclear Fusion
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Fort Lewis College
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Outline
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•
•
•
Solar interior
Fusion
Solar evolution
Stars
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Fort Lewis College
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Tutoring
• Wednesday 4:30-6:00
• Berndt 640
• USE IT OR LOSE IT
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Fort Lewis College
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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
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Fort Lewis College
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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
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Fort Lewis College
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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
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Fort Lewis College
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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
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Fort Lewis College
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Compared to the Earth, the Sun’s
average density is:
A) lower
B) about the same
C) much greater
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Fort Lewis College
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Compared to the Earth, the Sun’s
average density is:
A) lower
B) about the same
C) much greater
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Fort Lewis College
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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
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Fort Lewis College
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Solar Atmosphere
•
Photosphere •
•
Chromosphere •
•
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pinkish color (from Ha line); can see during eclipse.
cooler temperature (~4500 K)
Transition zone/Corona •
•
•
What we see. (~5780 K)
Shift from absorption spectrum to emission spectrum
Corona very hot (~3 million K)
Solar Wind •
The Sun is evaporating!
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Fort Lewis College
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Figure 9.10
Solar
Chromosphere
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Fort Lewis College
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Figure 9.12
Solar Corona
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Fort Lewis College
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Figure 9.24
Active
Corona
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Fort Lewis College
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Figure 9.13
Solar Atmospheric Temperature
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Fort Lewis College
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What about the internal structure?
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Fort Lewis College
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Solar Composition
Element
H
Number
Percent
91.2
Mass
Percent
71
He
8.7
27.1
O
0.078
0.97
C
0.043
0.4
N
0.0088
0.096
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Fort Lewis College
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Figure 9.2
Solar Structure
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Fort Lewis College
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Internal Structure
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Core •
•
Radiation Zone •
•
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•
temperatures hot enough for nuclear reactions
(~15 million K)
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.
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Fort Lewis College
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Figure 9.6
Solar Interior
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Fort Lewis College
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How do we know what is inside the Sun?
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Fort Lewis College
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How do we know what is inside the Sun?
Standard model
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Fort Lewis College
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Figure 9.4
Stellar Balance
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Fort Lewis College
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Figure 9.5
Solar Oscillations
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Fort Lewis College
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Figure 9.7
Solar Convection
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Fort Lewis College
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Figure 9.8
Solar Granulation
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Fort Lewis College
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Figure 9.11
Solar Spicules
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Fort Lewis College
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dynamic jets
5-10 minute life
possibly related
to seismic
activity
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.
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Fort Lewis College
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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.
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Fort Lewis College
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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
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Fort Lewis College
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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
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Fort Lewis College
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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.
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Fort Lewis College
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Fort Lewis College
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Nuclear Fusion
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Fort Lewis College
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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
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Fort Lewis College
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Nuclear Fusion
• Combining light nuclei into heavy
ones.
nucleus 1 + nucleus 2 = nucleus 3 + energy
• Law of conservation of mass and
energy
E = mc2
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Fort Lewis College
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Figure 9.25
Proton Interactions
• Like charges (two
protons) repel by
electromagnetic
force.
• With enough energy
(temperature) and
pressure, can
overcome EM force
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Fort Lewis College
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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.
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Fort Lewis College
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Figure 9.26
Solar Fusion
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Fort Lewis College
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Proton-Proton chain
• Neutrinos - “little neutral one” are
almost mass-less, and react with
almost nothing.
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Fort Lewis College
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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.
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Fort Lewis College
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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.
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Fort Lewis College
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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?
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Fort Lewis College
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