Download The Sun Groove– Kyle Chismar (Phys133

The Sun Groove– Kyle Chismar
(Phys133-08 student)
http://www.bartol.udel.edu/~owocki/phys133/ECP/Chismar-Kyle-1RightNow.mp4
Assignments
•  Read sec. 11.1-11.2 of Ch. 11
•  Do Online quizzes 04 and 05 for practice
–  doesn’t count for HW grade
•  Begin reading Ch. 12
© 2015 Pearson Education, Inc.
Midterm1 Exam results
•  Median score 74 (71 w/o extra credit)
•  Multiple choice answer key on webpage
•  Grade distribution
20
15
10
5
0
F
D-
D
D+
C-
C
C+
B-
B
B+
A-
A
Midterm1 Exam results
•  Short answer % vs. Multiple choice %:
100
80
sa
60
40
20
0
0
20
40
60
mc
80
100
Lecture Outline
Chapter 11:
Our Star
© 2015 Pearson Education, Inc.
11.1 A Closer Look at the Sun
Our goals for learning:
•  Why does the Sun shine?
•  What is the Sun's structure?
© 2015 Pearson Education, Inc.
Why does the Sun shine?
© 2015 Pearson Education, Inc.
Is it on FIRE?
© 2015 Pearson Education, Inc.
Is it on FIRE?
Chemical Energy Content
~ 10,000 years
Luminosity
© 2015 Pearson Education, Inc.
Is it on FIRE? … NO!
Chemical Energy Content
~ 10,000 years
Luminosity
© 2015 Pearson Education, Inc.
Is it CONTRACTING?
© 2015 Pearson Education, Inc.
Is it CONTRACTING?
Gravitational Potential Energy
~ 25 million years
Luminosity
© 2015 Pearson Education, Inc.
Is it CONTRACTING? … NO!
Gravitational Potential Energy
~ 25 million years
Luminosity
© 2015 Pearson Education, Inc.
E = mc2
—Einstein, 1905
It is powered by NUCLEAR ENERGY!
Nuclear Potential Energy (core)
~ 10 billion years
Luminosity
© 2015 Pearson Education, Inc.
Weight of upper layers
compresses lower
layers.
© 2015 Pearson Education, Inc.
Gravitational
equilibrium:
Gravity pulling
in balances
pressure
pushing out.
© 2015 Pearson Education, Inc.
Energy balance:
Thermal energy
released by
fusion in core
balances
radiative energy
lost from surface.
© 2015 Pearson Education, Inc.
Gravitational
contraction…
provided energy
that heated the core
as the Sun was
forming.
Contraction stopped
when fusion started
replacing the
energy radiated into
space.
© 2015 Pearson Education, Inc.
What is the Sun's structure?
© 2015 Pearson Education, Inc.
Radius:
6.9 ✕ 108 m
(109 times Earth)
Mass:
2 ✕ 1030 kg
(300,000 Earths)
Luminosity:
3.8 ✕ 1026 watts
© 2015 Pearson Education, Inc.
Solar wind:
A flow of
charged
particles from
the surface of
the Sun
© 2015 Pearson Education, Inc.
Corona:
Outermost
layer of
solar
atmosphere
~ 1 million K
© 2015 Pearson Education, Inc.
Chromosphere:
Middle layer of
solar atmosphere
~ 104–105 K
© 2015 Pearson Education, Inc.
Photosphere:
Visible surface
of the Sun
~ 6000 K
© 2015 Pearson Education, Inc.
Convection
zone:
Energy
transported
upward by
rising hot gas
© 2015 Pearson Education, Inc.
Radiation
zone:
Energy
transported
upward by
photons
© 2015 Pearson Education, Inc.
Core:
Energy
generated by
nuclear fusion
~ 15 million K
© 2015 Pearson Education, Inc.
What have we learned?
•  Why does the Sun shine?
–  Chemical and gravitational energy sources
could not explain how the Sun could sustain
its luminosity for more than about 25 million
years.
–  The Sun shines steadily because nuclear
fusion in the core maintains both
gravitational equilibrium between pressure
and gravity and energy balance between
thermal energy released in core and radiative
energy lost from the Sun's surface.
© 2015 Pearson Education, Inc.
What have we learned?
•  What is the Sun's structure?
–  From inside out, the layers are
•  Core
•  Radiation zone
•  Convection zone
•  Photosphere
•  Chromosphere
•  Corona
© 2015 Pearson Education, Inc.
11.2 Nuclear Fusion in the Sun
Our goals for learning:
•  How does nuclear fusion occur in the Sun?
•  How does the energy from fusion get out of the
Sun?
•  How do we know what is happening inside the
Sun?
© 2015 Pearson Education, Inc.
How does nuclear fusion occur in the Sun?
© 2015 Pearson Education, Inc.
Fission
Fusion
Big nucleus splits into
smaller pieces.
Small nuclei stick together
to make a bigger one.
(Nuclear power plants)
(Sun, stars)
© 2015 Pearson Education, Inc.
High temperatures
enable nuclear
fusion to happen
in the core.
© 2015 Pearson Education, Inc.
The Sun releases energy by fusing four hydrogen
nuclei into one helium nucleus.
© 2015 Pearson Education, Inc.
The Proton–proton chain is how hydrogen fuses
into helium in the Sun.
© 2015 Pearson Education, Inc.
IN
4 protons
OUT
4He nucleus
2 gamma rays
2 positrons
2 neutrinos
Total mass is
0.7% lower.
© 2015 Pearson Education, Inc.
Thought Question
What would happen inside the Sun if a slight rise in
core temperature led to a rapid rise in fusion
energy?
A.  The core would expand and heat up slightly.
B.  The core would expand and cool.
C.  The Sun would blow up like a hydrogen bomb.
© 2015 Pearson Education, Inc.
Thought Question
What would happen inside the Sun if a slight rise
in core temperature led to a rapid rise in fusion
energy?
A.  The core would expand and heat up slightly.
B.  The core would expand and cool.
C.  The Sun would blow up like a hydrogen bomb.
Solar thermostat keeps the rate of fusion steady.
© 2015 Pearson Education, Inc.
Solar Thermostat
Decline in core temperature
causes fusion rate to drop,
so core contracts and heats
up.
© 2015 Pearson Education, Inc.
Rise in core temperature
causes fusion rate to rise,
so core expands and cools
down.
How does the energy from fusion get out of
the Sun?
© 2015 Pearson Education, Inc.
Energy gradually leaks out of the radiation zone in
the form of randomly bouncing photons.
© 2015 Pearson Education, Inc.
Convection (rising hot
gas) takes energy to the
surface.
© 2015 Pearson Education, Inc.
Bright blobs on
photosphere where hot
gas reaches the surface
© 2015 Pearson Education, Inc.
How do we know what is happening inside
the Sun?
© 2015 Pearson Education, Inc.
We learn about the inside of the Sun by
•  making mathematical models
•  observing solar vibrations
•  observing solar neutrinos
© 2015 Pearson Education, Inc.