Chapter 9 The Sun 2017 Pearson Education Inc Units of Chapter 9 The Sun in Bulk The Solar Interior The Solar Atmosphere The Active Sun The Heart of the Sun Summary of Chapter 9 2017 Pearson Education Inc ID: 621670
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Chapter
9 The Sun
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Units of Chapter 9
The Sun in Bulk
The Solar InteriorThe Solar AtmosphereThe Active SunThe Heart of the SunSummary of Chapter 9
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9.1
The Sun
in Bulk
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9.1 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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9.1 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
×
0
26
W
—
the equivalent
of 10 billion 1-megaton
nuclear bombs per second.
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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.
9.2 The Solar Interior
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9.2 The Solar Interior
Doppler shifts of solar spectral lines indicate a complex pattern of vibrations.
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9.2 The Solar Interior
Solar density and temperature,
according to the standard solar
model
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9.2 The Solar Interior
Energy transport:
The radiation zone is relatively transparent; the cooler convection zone is opaque.
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9.2 The Solar Interior
The visible top layer of
the convection zone is
granulated, with areas
of upwelling material
surrounded by areas
of sinking material.
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9.3 The Solar Atmosphere
Spectral analysis can tell us what elements are present, but only in the chromosphere and photosphere.
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9.3 The Solar Atmosphere
The cooler chromosphere is above the photosphere.
It is difficult to see directly, as the photosphere is too bright, unless the Moon covers the photosphere
and not the chromosphere during eclipse.
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9.3 The Solar Atmosphere
Small solar storms in chromosphere emit spicules.
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9.3 The Solar Atmosphere
Solar corona can be seen during eclipse if both photosphere and chromosphere are blocked.
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9.3 The Solar Atmosphere
Corona is much hotter than layers below it. It must have a heat source, probably electromagnetic interactions.
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9.4 The Active Sun
Sunspots
appear dark because they are slightly cooler than their surroundings.
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9.4 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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9.4 The Active Sun
The rotation of the Sun drags magnetic field lines around with it, causing kinks.
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9.4 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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9.4 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: There are few, if any, sunspots.
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9.4 The Active Sun
Areas around sunspots are active; large eruptions may occur in the photosphere.
Solar prominence is a large sheet of ejected gas.
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9.4 The Active Sun
Solar flare
is a large explosion on the Sun
’
s surface, emitting an amount of energy similar to a prominence, but in seconds or minutes rather than days or weeks.
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9.4 The Active Sun
A
coronal mass ejection
emits charged particles that can affect Earth.
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9.4 The Active Sun
Solar wind
escapes the Sun mostly through coronal holes, which can be seen in X-ray images. The coronal hole is the dark V-shaped region.
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9.4 The Active Sun
Solar corona
changes along with the sunspot cycle. It is much larger and more irregular at sunspot peak.
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9.5 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 kelvins.
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9.5 The Heart of the Sun
The process that powers most stars is a three-step fusion process, the proton–proton chain.
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9.5 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 gives us a direct picture of what is happening in the core.
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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9.5 The Heart of the Sun
Neutrino observatories
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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 are the photosphere, chromosphere, and corona. The photosphere is the visible “
surface
”
of the Sun. 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.
© 2017 Pearson Education, Inc.