Download Earth Science 24.3B The Sun`s Interior

Earth Science 24.3B The Sun’s Interior
The Solar Interior
5/6/2010
Earth Science 24.3 The Sun
The Solar Interior:
 The interior of the sun can not be
observed directly.
 For that reason, all that we know
about it is based on information
acquired from the energy it
radiates and from theoretical
studies.
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Earth Science 24.3 The Sun
Nuclear Fusion:
 Deep in it’s interior, the sun
produces energy by a process
known as nuclear fusion.
 This nuclear reaction converts four
hydrogen nuclei into the nucleus of
a helium atom.
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Earth Science 24.3 The Sun
 During nuclear fusion, energy is
released because some matter is
actually converted to energy.
 How does the process of nuclear
fusion work?
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Earth Science 24.3 The Sun
 Consider the four hydrogen atoms
have a combined atomic mass of
4.032 atomic mass units ( 4 X 1.008)
whereas the atomic mass of helium is
4.003 atomic mass units. ( a
difference of 0.029 units)
 This tiny difference is emitted as
energy according to Einstein’s
equation ( E = mc2).
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Earth Science 24.3 The Sun
 According to Einstein’s equation,
seen at right, E equals energy, m
equals the mass, and c equals the
speed of light.
E = energy
M = mass
C = speed of light
(300,000 mp/s)
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Earth Science 24.3 The Sun
 Because the speed of light (c) is
great (300,000 kilometers per
second), the amount of energy
released from even a small amount of
material is enormous.
 The hydrogen bomb the United
States military developed was made
possible by creating such a reaction.
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Earth Science 24.3 The Sun
 The conversion of just one pinheads
worth of hydrogen to helium
generates more energy than
burning thousands of tons of coal.
 Most of this energy is in the form
of high-energy photons that work
their way toward the solar surface.
 The photons are absorbed and
reemitted many times until they
reach a layer just below the
photosphere.
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Earth Science 24.3 The Sun
 Here, convection currents help
transport this energy to the solar
surface, where it radiates through
the transparent chromosphere and
corona.
 Only a small percentage of the
hydrogen in the nuclear reaction is
actually converted to energy.
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Earth Science 24.3 The Sun
 Nevertheless, the sun is consuming
600 million tons of hydrogen each
second; about 4 million tons are
converted to energy.
 As hydrogen is consumed, the
product of this reaction, helium,
forms the solar core, which
continually grows in size.
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Earth Science 24.3 The Sun
 Just how long can the sun produce
energy at it’s present rate before
all of it’s hydrogen fuel is
consumed?
 Even at the enormous rate of
consumption, the sun, has enough
fuel to last easily for another 100
billion years.
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Earth Science 24.3 The Sun
 However, evidence from observing
other stars indicates that the sun
will grow dramatically and engulf
the Earth long before all of it’s
hydrogen is gone.
 It is thought that a star the size of
the sun can exist in it’s present
stable state for 10 billion years.
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Earth Science 24.3 The Sun
 As the sun is already 4.5 billion
years old, it is “middle aged” at
present.
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Earth Science 24.3 The Sun
 For fusion to occur however, the
sun’s internal temperature must
have reached several million
degrees.
 What caused this increase in
temperature?
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Earth Science 24.3 The Sun
 The solar system is believed
to have formed from an
enormous compressed cloud
of dust and gases, mostly
hydrogen.
 When gases are
compressed, their
temperature increases due
to the higher pressure they
are under.
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Earth Science 24.3 The Sun
 All of the bodies in our solar
system are compressed.
 The sun however, because of it’s
enormous size, was the only object
to become hot enough for nuclear
fusion to occur.
 Astronomers currently calculate it’s
internal temperature at 15 million
degrees Kelvin (K).
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Earth Science 24.3 The Sun
 The planet Jupiter is basically a
hydrogen-rich ball as well.
 If it were about 10 times more
massive, it too would have
converted into a star capable of
nuclear fusion.
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Earth Science 24.3 The Sun
 The idea of one star orbiting
another seems odd but recent
evidence indicates that about 50
percent of the stars in the
universe occur in pairs or
multiple stars within a single
system.
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