Download Ch 14 Mar 7

Chapter 14
Our Star
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Why does the Sun Shine?
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Is it on FIRE?
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Is it on FIRE?
Chemical energy content
Luminosity
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~ 10,000 years
Is it on FIRE? …NO!
Chemical energy content
Luminosity
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~ 10,000 years
Insert TCP 6e Chapter 14 opener
Is it CONTRACTING?
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Is it CONTRACTING?
Gravitational potential energy
Luminosity
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~ 25 million years
Is it CONTRACTING?...NO!
Gravitational potential energy
Luminosity
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~ 25 million years
Why does the Sun shine?
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Insert TCP 6e Figure 14.1
Weight of upper layers
compresses lower layers.
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Gravitational
equilibrium:
There is a
balance between
the outward
fusion pressure
and the inward
pressure, due to
gravity.
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What is the Sun’s structure?
Insert TCP 6e Figure 14.3
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Solar wind:
A flow of
charged
particles from
the surface of
the Sun
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Corona:
Outermost
layer of solar
atmosphere and
seen only
during a total
solar eclipse.
~1 million K
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Chromosphere:
Middle layer of
solar atmosphere
and seen only
during a total solar
eclipse.
~ 104–105 K
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Photosphere:
Visible surface of
Sun
~ 6000 K
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Convection Zone:
Energy transported
upward by rising
hot gas
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Radiation Zone:
Energy transported
upward by photons
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Core:
Energy generated
by nuclear fusion
~ 15 million K
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Clicker Question
What is the surface we see?
A.
B.
C.
D.
corona
photosphere
chromosphere
solar wind
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Clicker Question
What is the surface we see?
A.
B.
C.
D.
corona
photosphere
chromosphere
solar wind
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Clicker Question
What layer is the hottest?
A. corona
B. photosphere
C. chromosphere
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Clicker Question
What layer is the hottest?
A. corona
B. photosphere
C. chromosphere
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Clicker Question
What layer is the coolest?
A. corona
B. photosphere
C. chromosphere
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Clicker Question
What layer is the coolest?
A. corona
B. photosphere
C. chromosphere
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How does nuclear fusion occur in
the Sun?
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Fission
Fusion
Big nucleus splits into
smaller pieces.
Small nuclei stick
together to make a
bigger one.
(Example: nuclear
power plants)
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(Example: the Sun, stars)
High temperatures
enable nuclear
fusion to happen in
the core.
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The Sun releases energy by fusing four hydrogen nuclei into one
helium nucleus.
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The proton–proton chain is how hydrogen fuses into helium in Sun.
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IN
4 protons
OUT
4He nucleus
2 gamma rays
2 positrons
2 neutrinos
Total mass is
0.7% lower.
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Proton-Proton Chain in Gory Detail
Step 1:
1H
1H --> 2H + e+ + 
+
1
1
1
1H is
1
a hydrogen nucleus - subscript is the number of protons
in nucleus, superscript is the number of protons + neutrons in
the nucleus. Hydrogen nucleus has 1 proton, 0 neutrons.
2H is a deuterium nucleus (hydrogen isotope) with 1 proton
1
and 1 neutron in nucleus.
e+ is a positron or antiparticle of the e-. When e+ and e- meet,
e+ + e- __ > 2  two gamma rays are produced
is a neutrino and helps to carry away energy.
Step 2:
3He
2
2
2H --> 3He + 
+
1
1
2
is a helium isotope,  is a gamma ray.
Step 3:
4He
1H
3He
3He --> 4He + 1H + 1H
+
2
2
2
1
1
is ordinary or ‘balloon’ helium.
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Clicker Question
What is e+?
A.
B.
C.
D.
E.
electron
positron
Neutron
proton
neutrino
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Clicker Question
What is e+?
A.
B.
C.
D.
E.
electron
positron
Neutron
proton
neutrino
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Clicker Question
What is 2H1?
A.
B.
C.
D.
gamma ray
helium nucleus
deuterium nucleus
ordinary hydrogen nucleus
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Clicker Question
What is 2H1?
A.
B.
C.
D.
gamma ray
helium nucleus
deuterium nucleus
ordinary hydrogen nucleus
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Clicker Question
What is ?
A.
B.
C.
D.
E.
gamma ray
positron
Neutron
proton
neutrino
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Clicker Question
What is ?
A.
B.
C.
D.
E.
gamma ray
positron
Neutron
proton
neutrino
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Clicker Question
What is ?
A.
B.
C.
D.
E.
gamma ray
positron
Neutron
proton
neutrino
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Clicker Question
What is ?
A.
B.
C.
D.
E.
gamma ray
positron
Neutron
proton
neutrino
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