Sun – chapter 16
Composition, Energy source,
Structure, “normal life” changes
Goals & Outcomes
• Explain how electromagnetic radiation and astronomical
instruments are used to reveal the properties of stars and
galaxies.
• Diagram the process of nuclear fusion.
• Learn about some problems astronomers and astrophysicists
are trying to solve, and understand the methods scientists are
using to try to solve these problems.
• Develop a sense of what scientists know about the overall
universe, its constituents, and our location
• Diagram and explain radiative transport in the Sun. Explain the
causes of surface features on the Sun.
Major Sun facts
• What’s a star?
– _______________________
– ________, so it must ___________________.
Must protect your body if in space!
• Which ___________________?
– ____________________________________
– Other: O=1%, C=0.4%, Fe=0.14%, N=0.1%,
Si, Mg, Ne, S 0.040.1%.
• How do we know these numbers?
Sun’s Age
• Easy to measure: ___________________
• Can figure out ______________
• __________________ tell us age must be
____________________________
• _________________ tell us ___________
• What can make the Sun shine so bright for
so long?
Sun
The picture shown to the
right is taken using the
Hydrogen 3  2 transition
(red colored, called H-alpha
Power Sources and how long Sun could shine
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This is discussed on page _________.
See common
____________________________________misconception
__________
____________________________________
____________________________________
Until 1920, ___ idea _____________________.
– _____________________________________
• _______________. (Do humans use _______?)
• ______________________________________
–
(For more details, see figure 14.7 – not on test)
– Every sec: ________tons ___ into ________tons __.
– Can do this for a total of _______________ years
– How old is Sun. How much time left?
• Review: what’s H atom made of? He atom?
Why is fusion difficult for people & Sun?
• What is nuclear fusion? What’s in the nucleus?
• Why would they be ____________________?
– Fig 14.6, top
• What must happen to ___________________?
• _____________ “turns on” when ___________
– Fig 14.6, bottom
• Why ________________________________?
• How do you overcome this?
• Where are conditions right?
– ____________________________________ water
• Humans use more energy than fusion releases,
with current technology. Wait 30 years!
At what temperature does helium
fuse with another helium?
1. Also at 15 million K
2. Less than 15 million K
3. More than 15 million K
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Calif. Elementary School Science
Standards for nuclear processes
•
From California Science Standards, high
school
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Students know protons and neutrons in the nucleus
are held together by nuclear forces that overcome
the electromagnetic repulsion between the protons
Students know the energy release per gram of
material is much larger in nuclear fusion or fission
reactions than in chemical reactions. The change in
mass (calculated by E = mc2 ) is small but
significant in nuclear reactions.
Students know the Sun is a typical star and is
powered by nuclear reactions, primarily
the fusion of hydrogen to form helium.
Structure & evolution of the Sun
• Start with a clicker question.
Star lives – a constant struggle
Figure _________, page _______
• Gravity tries to ____________________
• Shrinking wins until …
• Some source of _____________________
– What is the Sun? (What is any star?)
– Big sphere of _________________________.
– ____________________________________
_____________________________.
• Think of an example of balls of gas in your
everyday life.
• What do you do to _________________________
(i.e. _________________________)?
Gravity & Pressure imbalance
(pp. __________) Figure 14.8
• If _________________ than gas pressure,
what happens?
– Gas ___________ and becomes _____ when
it _________________.
– Fusion in the core will _________. Star _____
• If ______________________ than gravity,
what happens?
– Gas ___________ and becomes _____ when
it _____________.
– Fusion in the core will _________. Star _____
Review question: Does the mass of
the Sun change over its lifetime?
1. Yes
2. No
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Review question: How does the mass
of the Sun change over its lifetime?
1. Not at all
2. A little bit, but not noticeable
3. The Sun’s mass changes noticeably
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Sun’s structure –
radiation transport
• See figure _______, page ______.
• ___________________________
– ______________________ K
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______________ – where energy carried by ______
_______________ – energy carried by ____________
________________ – ________________________
______ – ______________________ – see pic above
– How could we see this?
• _________________ comes off the Sun.
– _______________________________________.
– Causes ____________________ (aurora borealis/australis).
– Affect atmospheres, magnetism
Radiation & Convection Zones
• Core is hot – thermal emitter
• __________________________________
– _____________________________________________
• _____________________________________. Figure ___________
– “_________________ photons”
• Takes __________________________ to “walk” from core  outside
• ___________________________________
–
–
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Outer layers are ________________, stuff gets _________
Photons get “_______________”
______________. _______________. _________________
Movement is visible through ECC scopes!
See figure ____________
• ___________________________
– __________________________. Outside temp: _______ K.
– Quick review question: how long does it take light to get here
once it leaves the Sun?
Evil scientist magically turns off
fusion. Would you notice after 6
minutes?
1. Yes
2. No
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Evil scientist magically turns off
fusion. Would you notice after 10
minutes?
1. Yes
2. No
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The amount of Helium in the Sun
is:
1. Increasing
2. Decreasing
3. Staying the same
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What’s happening to the number of
particles in the Sun’s core?
1. Increasing
2. Decreasing
3. Staying the same
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Slow evolution of the Sun
• What happens to core gas pressure as a result
of ________________________________?
• What happens to the core? It _____ and _____.
• That causes what?
• Balance restored!
• What happens to fusion rate?
• What happens to the Sun’s luminosity?
Studying Sun’s interior
• Helio__________________________
– See figure 14.11
– ____________________ tell us about insides
– Strongest clues about interior of the Sun
– Figure 14.12 shows results
Solar Neutrinos
• ________________(turning proton into neutron).
– 3% of Sun’s energy in neutrino form. 97% light.
• ________________________________________
– _________________________________________
• _________________they interact with stuff
– ___________. See figure 14.14 page 506
– 60 billion/cm2/sec. New million ton detectors “see” ___
neutrinos per day. [New versions: looking for dark
matter!]
• We saw 1/3 to ___________________from fusion
• HUGE puzzle
• Solution (May 2001): neutrinos _______________
– ____________________weren’t detectable in past.
Another
neutrino
detector
• Japanese Super
Kamiokande
• filled with
50,000 tons of
water
• 13,000 light
detectors
(seen on wall)
Link to Earth - spots
• What are the
spots?
• Hotter or colder
than the rest of the
photosphere?
• Like ___________
______________,
they’re _________
_______________
______________________
• ____________________:
–_____________________
–______________________
–___________________ (probably)
• _________ Rotation: figure _____
Solar _____________
• Sunspots go through _________________ –
few spots to many back to few.
– 2007 “Solar _______________________”
– When is the next “Solar maximum”
•
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Cycle isn’t a perfect clock
Some cycles stronger than others
Figures 14.22 & 14.23
There might be a link to _______________ /
_____. But __________________________.
Summary
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We know the Sun fuses based on its age
Fusion energy source & productS
Composition (general)
Why fusion is difficult (repulsion, strong force)
Gravity vs. pressure. How currently balanced?
Different “layers” of Sun, a little about each
Neutrinos – what, where, problem?
Magnetic fields
Solar Cycle – time, observable results
A PUZZLE: north pole is warmer than south pole by
80,000K all the time. (Does not flip when magnetic
field does.) Stay tuned.