Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. Chapter
10 Our Star Slide 2 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. 10.1 A Closer Look at the Sun Our goals for learning:
Why does the Sun shine? What is the Suns structure? Slide 3 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Why does the Sun
shine? Slide 4 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Is it on FIRE? Slide 5 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Is it on FIRE? Luminosity ~ 10,000 years Chemical
Energy Content Slide 6 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Is it on FIRE? NO! Luminosity ~ 10,000 years Chemical
Energy Content Slide 7 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Is it CONTRACTING? Slide 8 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Luminosity Gravitational
Potential Energy Is it CONTRACTING? ~ 25 million years Slide 9
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Luminosity Gravitational Potential Energy Is it CONTRACTING? NO! ~
25 million years Slide 10 Scott Hildreth Chabot College Adapted
from Essential Cosmic Perspective 4 th ed. Copyright 2007 by
Pearson Publishing. It is powered by NUCLEAR ENERGY! Luminosity ~
10 billion years Nuclear Potential Energy (core) E = mc 2 Einstein,
1905 Slide 11 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Weight of upper layers compresses lower layers Slide 12 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Gravitational
equilibrium: Energy provided by fusion maintains the pressure.
Slide 13 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Gravitational contraction provided energy that heated the core as
the Sun was forming. Contraction stopped when fusion began
replacing the energy radiated into space. Slide 14 Scott Hildreth
Chabot College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. What is the Suns structure?
Slide 15 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Radius: 6.9 10 8 m (109 times Earth) Mass: 2 10 30 kg (300,000
Earths) Luminosity: 3.8 10 26 watts Slide 16 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Solar wind: A flow of charged
particles (electrons, protons, some helium nuclei) from the surface
of the Sun Creates Aurora Slide 17 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. Corona: Outermost layer of solar atmosphere
~1 million K Seen in X-rays Shows emission lines + faint continuous
spectrum Slide 18 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Chromosphere: Middle layer of solar atmosphere ~ 10 4
10 5 K Seen in UV Light Shows emission lines Features: Prominences,
Flares, Slide 19 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Photosphere: Visible surface of Sun ~ 6,000 K Seen in
Visible Light Shows Absorption lines Sunspots! Cut-away Section of
the Sun Slide 20 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Convection zone: Beneath Photosphere Creates granules
we see Energy transported upward by rising hot gas Slide 21 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Radiation zone: Energy
transported upward by Gamma Ray & X-ray photons Determine
extent based on computer models Slide 22 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Core: Energy generated by
nuclear fusion ~ 15 million K Generates gamma rays Inner 10% of sun
Slide 23 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
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 because gravitational
equilibrium keeps its core hot and dense enough to release energy
through nuclear fusion. Slide 24 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. What is the Suns structure? From inside out,
the layers are: Core Radiation zone Convection zone Photosphere
Chromosphere Corona These we cant see we model with computer
simulations These we CAN see and measure with X-ray, UV, and
visible-light telescopes in orbit & on Earth Slide 25 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. 10.2 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? Slide 26 Scott Hildreth
Chabot College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. How does nuclear fusion occur
in the Sun? Fusion is the UNITING of light atomic nuclei into
heavier nuclei, releasing binding energy in the form of gamma ray
radiation and other particles Slide 27 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Fission Big nucleus splits
into smaller pieces (Nuclear power plants) Fusion Small nuclei
stick together to make a bigger one (Sun, stars) Slide 28 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. High temperatures
enable nuclear fusion to happen in the core. Slide 29 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Sun releases energy by
fusing four hydrogen nuclei into one helium nucleus. Slide 30 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Protonproton chain is
how hydrogen fuses into helium in Sun Slide 31 Scott Hildreth
Chabot College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. IN 4 protons OUT 4 He nucleus
2 gamma rays 2 positrons 2 neutrinos Total mass is 0.7% lower.
Slide 32 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
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. Slide 33
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. 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
burning rate steady Slide 34 Scott Hildreth Chabot College Adapted
from Essential Cosmic Perspective 4 th ed. Copyright 2007 by
Pearson Publishing. Solar Thermostat Decline in core temperature
causes fusion rate to drop, so core contracts and heats up Rise in
core temperature causes fusion rate to rise, so core expands and
cools down Structure of the Sun Slide 35 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. How does the energy from
fusion get out of the Sun? Slide 36 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. Energy gradually leaks out of the radiation
zone in the form of randomly bouncing photons. Slide 37 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Convection (rising hot
gas) takes energy to the surface. Slide 38 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Bright blobs on photosphere
where hot gas reaches the surface Slide 39 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. How do we know what is
happening inside the Sun? Slide 40 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. We learn about the inside of the Sun by
making mathematical models. observing solar vibrations. observing
solar neutrinos. Slide 41 Scott Hildreth Chabot College Adapted
from Essential Cosmic Perspective 4 th ed. Copyright 2007 by
Pearson Publishing. Patterns of vibration on the surface tell us
about what the Sun is like inside. Slide 42 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Data on solar vibrations
agree with mathematical models of solar interior. Slide 43 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Neutrinos created
during fusion fly directly through the Sun. Observations of these
solar neutrinos can tell us whats happening in the core. Slide 44
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. Solar
neutrino problem: Early searches for solar neutrinos failed to find
the predicted number. Slide 45 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. Solar neutrino problem: Early searches for
solar neutrinos failed to find the predicted number. More recent
observations find the right number of neutrinos, but some have
changed form. Slide 46 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. What have we learned? How does nuclear fusion occur in
the Sun? The cores extreme temperature and density are just right
for the nuclear fusion of hydrogen to helium through the
protonproton chain. Gravitational equilibrium acts as a thermostat
to regulate the core temperature because the fusion rate is very
sensitive to temperature. Slide 47 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. What have we learned? How does the energy
from fusion get out of the Sun? Randomly bouncing photons carry it
through the radiation zone. The rising of hot plasma carries energy
through the convection zone to the photosphere. How do we know what
is happening inside the Sun? Mathematical models agree with
observations of solar vibrations and solar neutrinos. Slide 48
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. 10.3 The
SunEarth Connection Our goals for learning: What causes solar
activity? How does solar activity affect humans? How does solar
activity vary with time? Slide 49 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. What causes solar activity? Slide 50 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. Solar activity is like
weather Sunspots Solar flares Solar prominences All are related to
magnetic fields. Slide 51 Scott Hildreth Chabot College Adapted
from Essential Cosmic Perspective 4 th ed. Copyright 2007 by
Pearson Publishing. Sunspots Are cooler than other parts of the
Suns surface (4,000 K) Are regions with strong magnetic fields
Slide 52 Scott Hildreth Chabot College Adapted from Essential
Cosmic Perspective 4 th ed. Copyright 2007 by Pearson Publishing.
Zeeman Effect We can measure magnetic fields in sunspots by
observing the splitting of spectral lines Slide 53 Scott Hildreth
Chabot College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Charged particles spiral
along magnetic field lines. Slide 54 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. Loops of bright gas often connect sunspot
pairs. Slide 55 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. Magnetic activity causes solar flares that send bursts
of X-rays and charged particles into space. Slide 56 Scott Hildreth
Chabot College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. Magnetic activity also causes
solar prominences that erupt high above the Suns surface. Slide 57
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. The
corona appears bright in X-ray photos in places where magnetic
fields trap hot gas. Slide 58 Scott Hildreth Chabot College Adapted
from Essential Cosmic Perspective 4 th ed. Copyright 2007 by
Pearson Publishing. How does solar activity affect humans? Slide 59
Scott Hildreth Chabot College Adapted from Essential Cosmic
Perspective 4 th ed. Copyright 2007 by Pearson Publishing. Coronal
mass ejections send bursts of energetic charged particles out
through the solar system. Slide 60 Scott Hildreth Chabot College
Adapted from Essential Cosmic Perspective 4 th ed. Copyright 2007
by Pearson Publishing. Charged particles streaming from the Sun can
disrupt electrical power grids and disable communications
satellites. Slide 61 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. How does solar activity vary with time? Slide 62 Scott
Hildreth Chabot College Adapted from Essential Cosmic Perspective 4
th ed. Copyright 2007 by Pearson Publishing. The number of sunspots
rises and falls in 11-year cycles. Slide 63 Scott Hildreth Chabot
College Adapted from Essential Cosmic Perspective 4 th ed.
Copyright 2007 by Pearson Publishing. The sunspot cycle has
something to do with the winding and twisting of the Suns magnetic
field. Slide 64 Scott Hildreth Chabot College Adapted from
Essential Cosmic Perspective 4 th ed. Copyright 2007 by Pearson
Publishing. What have we learned? What causes solar activity? The
stretching and twisting of magnetic field lines near the Suns
surface causes solar activity. How does solar activity affect
humans? Bursts of charged particles from the Sun can disrupt
communications, satellites, and electrical power generation. How
does solar activity vary with time? Activity rises and falls in
11-year cycles.
