Transcript 09 Sun

Chapter 9
The Sun
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Chapter 9
The Sun
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Large Tsunami Shock Wave on the Sun
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SOHO
Solar and Helospheric Observatory
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NSO – New Mexico
Units of Chapter 9
The Sun in Bulk
The Solar Interior
The Solar Atmosphere
The Active Sun
The Heart of the Sun
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Question 1
The visible light we see
from our Sun comes
from which part?
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a) core
b) corona
c) photosphere
d) chromosphere
e) convection zone
The Sun in Bulk
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The Sun in Bulk
Interior structure
of the Sun
Outer layers are
not to scale.
The core is where
nuclear fusion
takes place.
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Question 2
The density of the
Sun is most
similar to that of
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a) a comet.
b) Jupiter.
c) Earth.
d) interstellar gas.
e) an asteroid.
The Sun in Bulk
Luminosity – total energy radiated by the Sun –
can be calculated from the fraction of that
energy that reaches Earth.
Total luminosity is
about 4 × 1026 W – the
equivalent of 10 billion
1-megaton nuclear
bombs per second.
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The Solar Interior
Mathematical models, consistent with
observation and physical principles, provide
information about the Sun’s interior.
In equilibrium,
inward gravitational
force must be
balanced by
outward pressure.
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Question 3
The Sun is
stable as a
star because
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a) gravity balances forces from pressure.
b) the rate of fusion equals the rate of fission.
c) radiation and convection balance.
d) mass is converted into energy.
e) fusion doesn’t depend on temperature.
The Solar Interior
Doppler shifts of solar spectral lines indicate a
complex pattern of vibrations.
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The Solar Interior
Solar density and
temperature, according
to the standard solar
model.
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The Solar Interior
Energy transport:
The radiation zone is relatively transparent; the
cooler convection zone is opaque.
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The Solar Interior
The visible top layer of
the convection zone is
granulated, with areas
of upwelling material
surrounded by areas
of sinking material.
Solar Granulation
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The Solar Atmosphere
Spectral analysis can tell us what elements are
present, but only in the chromosphere and
photosphere.
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The Solar Atmosphere
The cooler chromosphere is above the
photosphere.
Difficult to see
directly, as
photosphere is too
bright, unless Moon
covers photosphere
and not chromosphere
during eclipse
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The Solar Atmosphere
Small solar
storms in
chromosphere
emit spicules.
Solar Chromosphere
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The Solar Atmosphere
Solar corona can be
seen during eclipse
if both photosphere
and chromosphere
are blocked.
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The Solar Atmosphere
Corona is much hotter than layers below it – must
have a heat source, probably electromagnetic
interactions.
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The Active Sun
Sunspots appear dark
because slightly cooler
than surroundings.
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The Active Sun
Sunspots come
and go, typically
in a few days.
Sunspots are
linked by pairs
of magnetic
field lines.
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The Active Sun
The rotation of the Sun drags magnetic field
lines around with it, causing kinks.
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The Active Sun
The Sun has an 11-year
sunspot cycle, during
which sunspot
numbers rise, fall,
and then rise again.
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Question 7
The number of
sunspots and solar
activity in general
peaks
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a) every 27 days, the apparent rotation
period of the Sun’s surface.
b) once a year.
c) every 5½ years.
d) every 11 years.
e) approximately every 100 years.
The Active Sun
This is really a 22-year cycle, because the spots
switch polarities between the northern and
southern hemispheres every 11 years.
Maunder minimum: few, if any, sunspots.
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The Active Sun
Areas around sunspots are active; large
eruptions may occur in photosphere.
Solar prominence is large sheet of ejected gas.
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The Active Sun
Solar flare is a large
explosion on Sun’s
surface, emitting a
similar amount of
energy to a
prominence, but in
seconds or minutes
rather than days or
weeks.
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The Active Sun
A coronal mass ejection
emits charged particles
that can affect the Earth.
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Filament/Prominence Eruption
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The Active Sun
Solar wind escapes
Sun mostly through
coronal holes, which
can be seen in X-ray
images.
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The Active Sun
Solar corona
changes along with
sunspot cycle; is
much larger and
more irregular at
sunspot peak.
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Question 6
What is probably
responsible for the
increase in temperature
of the corona far from
the Sun’s surface?
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a) a higher rate of fusion
b) the Sun’s magnetism
c) higher radiation pressures
d) absorption of X rays
e) convection currents
The Heart of the Sun
Nuclear fusion requires
that like-charged nuclei
get close enough to
each other to fuse.
This can happen only
if the temperature is
extremely high – over
10 million K.
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The Heart of the Sun
The process that powers most stars is a threestep fusion process.
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Question 4
The proton–proton cycle
involves what kind of
fusion process?
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a) carbon (C) into oxygen (O)
b) helium (He) into carbon (C)
c) hydrogen (H) into helium (He)
d) neon (Ne) into silicon (Si)
e) oxygen (O) into iron (Fe)
The Heart of the Sun
Neutrinos are emitted directly from the core of
the Sun, and escape, interacting with virtually
nothing. Being able to observe these neutrinos
would give us a direct picture of what is
happening in the core.
Unfortunately, they are no more likely to interact
with Earth-based detectors than they are with the
Sun; the only way to spot them is to have a huge
detector volume and to be able to observe single
interaction events.
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Question 8
The solar neutrino
problem refers to
the fact that
astronomers
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a) cannot explain how the Sun is stable.
b) detect only one-third the number of
neutrinos expected by theory.
c) cannot detect neutrinos easily.
d) are unable to explain how neutrinos
oscillate between other types.
e) cannot create controlled fusion
reactions on Earth.
Question 5
A neutrino can escape
from the solar core
within minutes. How long
does it take a photon to
escape?
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a) minutes
b) hours
c) months
d) hundreds of years
e) about a million years
The Heart of the Sun
Neutrino observatories
Super Kamiokande, Japan
Sudbury Neutrino Observatory
Canada
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Summary of Chapter 9
• The Sun is held together by its own gravity
and powered by nuclear fusion.
• Outer layers of the Sun: photosphere,
chromosphere, corona. The corona is very hot.
• Mathematical models and helioseismology
give us a picture of the interior of the Sun.
• Sunspots occur in regions of high magnetic
fields; darker spots are cooler.
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Summary of Chapter 9, cont.
• Nuclear fusion converts hydrogen to helium,
releasing energy.
• Solar neutrinos come directly from the solar
core, although observations have told us more
about neutrinos than about the Sun.
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