EARTH & SPACE EARTH & SPACE SCIENCESCIENCE

Chapter 29 The SunChapter 29 The Sun

29.1 Structure of the Sun29.1 Structure of the Sun

29.1 Structure of the Sun 29.1 Structure of the Sun ObjectivesObjectives

Explain how the sun converts matter into Explain how the sun converts matter into energy in its core.energy in its core.

Compare the radiative and convective Compare the radiative and convective zones of the sun.zones of the sun.

Describe the three layers of the sun’s Describe the three layers of the sun’s atmosphere.atmosphere.

The Sun’s EnergyThe Sun’s Energy Using a device called a spectrograph, Using a device called a spectrograph,

scientists break up the sun’s light into a scientists break up the sun’s light into a spectrum. spectrum.

Dark lines form in the spectra of stars when Dark lines form in the spectra of stars when gases in the stars’ outer layers absorb gases in the stars’ outer layers absorb specific wavelengths of the light that passes specific wavelengths of the light that passes through the layers.through the layers.

By studying the spectrum of a star, scientists By studying the spectrum of a star, scientists can determine the amounts of elements that can determine the amounts of elements that are present in a star’s atmosphere.are present in a star’s atmosphere.

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The Sun’s EnergyThe Sun’s Energy Because each element produces a unique Because each element produces a unique

pattern of spectral lines, astronomers can pattern of spectral lines, astronomers can match the spectral lines of starlight to those match the spectral lines of starlight to those of Earth’s elements, and identify the elements of Earth’s elements, and identify the elements in the star’s atmosphere.in the star’s atmosphere.

Both hydrogen and helium occur in the sun. Both hydrogen and helium occur in the sun. About 75% of the sun’s mass is hydrogen, About 75% of the sun’s mass is hydrogen, and hydrogen and helium together make up and hydrogen and helium together make up about 99% of the sun’s mass. about 99% of the sun’s mass.

The sun’s spectrum reveals that the sun The sun’s spectrum reveals that the sun contains traces of almost all other chemical contains traces of almost all other chemical elements.elements.

The Sun’s EnergyThe Sun’s EnergyNuclear fusion is the process by which Nuclear fusion is the process by which

nuclei of small atoms combine to form a nuclei of small atoms combine to form a new, more massive nucleus; the process new, more massive nucleus; the process releases energyreleases energy

Nuclear fusion occurs inside the sun. Nuclear fusion occurs inside the sun. Nuclei of hydrogen atoms are the primary Nuclei of hydrogen atoms are the primary fuel for the sun’s fusion. fuel for the sun’s fusion.

Nuclear fusion produces most of the suns’ Nuclear fusion produces most of the suns’ energy and consists of three steps.energy and consists of three steps.

The Sun’s EnergyThe Sun’s Energy

In the first step, two hydrogen nuclei, or In the first step, two hydrogen nuclei, or protons, collide and fuse. protons, collide and fuse.

In this step, the positive charge of one of In this step, the positive charge of one of the protons is neutralized as that proton the protons is neutralized as that proton emits a particle called a positron.emits a particle called a positron.

As a result, the proton becomes a neutron As a result, the proton becomes a neutron and changes the original two protons into and changes the original two protons into a proton-neutron pair. a proton-neutron pair.

The Sun’s EnergyThe Sun’s Energy

In the second step, another proton combines In the second step, another proton combines with this proton-neutron pair to produce a with this proton-neutron pair to produce a nucleus made up of two protons and one nucleus made up of two protons and one neutron.neutron.

In the third step, two nuclei made up of two In the third step, two nuclei made up of two protons and one neutron collide and fuse. protons and one neutron collide and fuse.

As this fusion happens, two protons are As this fusion happens, two protons are released. The remaining two protons and two released. The remaining two protons and two neutrons are fused together and form a helium neutrons are fused together and form a helium nucleus. At each step, energy is released.nucleus. At each step, energy is released.

The Sun’s EnergyThe Sun’s Energy One of the final products of the fusion of One of the final products of the fusion of

hydrogen in the sun is always a helium hydrogen in the sun is always a helium nucleus.nucleus.

The helium nucleus has about 0.7% less mass The helium nucleus has about 0.7% less mass than the hydrogen nuclei that combined to form than the hydrogen nuclei that combined to form it do. it do.

The lost mass is converted into energy during The lost mass is converted into energy during the series of fusion reactions that forms helium.the series of fusion reactions that forms helium.

The energy released during the three steps of The energy released during the three steps of nuclear fusion causes the sun to shine and nuclear fusion causes the sun to shine and gives the sun its high temperature.gives the sun its high temperature.

The Sun’s EnergyThe Sun’s Energy

Nuclear Fusion Animation (1:49) - Nuclear Fusion Animation (1:49) - http://youtu.be/fSr3V498A3Ihttp://youtu.be/fSr3V498A3I

Solar Energy Nuclear Fusion in the Sun Solar Energy Nuclear Fusion in the Sun (3:44) - (3:44) - http://youtu.be/pusKlK1L5Tohttp://youtu.be/pusKlK1L5To

Mass Changing Into EnergyMass Changing Into Energy

The sun’s energy comes from fusion, and the The sun’s energy comes from fusion, and the mass that is lost during fusion becomes mass that is lost during fusion becomes energy.energy.

In 1905, Albert Einstein proposed that a small In 1905, Albert Einstein proposed that a small amount of matter yields a large amount of amount of matter yields a large amount of energy. energy.

This proposal was part of Einstein’s special This proposal was part of Einstein’s special theory of relativity.theory of relativity.

This theory included the equation:This theory included the equation: E = mcE = mc22

Mass Changing Into EnergyMass Changing Into Energy

In Einstein’s equation E = mcIn Einstein’s equation E = mc22, E represents , E represents energy produced; m represents the mass; energy produced; m represents the mass; and c represents the speed of light, which is and c represents the speed of light, which is about 300,000 km/s.about 300,000 km/s.

Einstein’s equation can be used to calculate Einstein’s equation can be used to calculate the amount of energy produced from a given the amount of energy produced from a given amount of matter.amount of matter.

By using Einstein’s equation, astronomers By using Einstein’s equation, astronomers were able to explain the huge quantities of were able to explain the huge quantities of energy produced by the sun.energy produced by the sun.

The Sun’s InteriorThe Sun’s Interior Careful studies of motions on the sun’s surface Careful studies of motions on the sun’s surface

have supplied more detail about what is have supplied more detail about what is happening inside the sun. happening inside the sun.

The parts of the sun include the core, the radiative The parts of the sun include the core, the radiative zone, and the convective zone.zone, and the convective zone.

At the center of the sun is the core. At the center of the sun is the core. The core makes up 25% of the sun’s total The core makes up 25% of the sun’s total

diameter of 1,390,000 km. diameter of 1,390,000 km. The temperature of the core is about 15,000,000 The temperature of the core is about 15,000,000

ºC. ºC. The core is made up entirely of ionized gas, and is The core is made up entirely of ionized gas, and is

10 times as dense as iron.10 times as dense as iron.

The Sun’s InteriorThe Sun’s Interior The radiative zone is the zone of the sun’s interior The radiative zone is the zone of the sun’s interior

that is between the core and the convective zone that is between the core and the convective zone and in which energy moves by radiation.and in which energy moves by radiation.

The radiative zone of the sun surrounds the core. The radiative zone of the sun surrounds the core. The temperature of the radiative zone ranges The temperature of the radiative zone ranges

from about 2,000,000ºC to 7,000,000 ºC .from about 2,000,000ºC to 7,000,000 ºC . In the radiative zone, energy moves outward in In the radiative zone, energy moves outward in

the form of electromagnetic waves, or radiation.the form of electromagnetic waves, or radiation.

The Sun’s InteriorThe Sun’s Interior

Convective zone the region of the sun’s interior that Convective zone the region of the sun’s interior that is between the radiative zone and the photosphere is between the radiative zone and the photosphere and in which energy is carried upward by convectionand in which energy is carried upward by convection

The convective zone surrounds the radiative zone. The convective zone surrounds the radiative zone. The temperature of the convective zone is about The temperature of the convective zone is about

2,000,000ºC.2,000,000ºC. Energy produced in the core moves through this Energy produced in the core moves through this

zone by convection.zone by convection. Convection is the transfer of energy by moving Convection is the transfer of energy by moving

matter.matter.

The Sun’s AtmosphereThe Sun’s Atmosphere

The sun’s atmosphere surrounds the The sun’s atmosphere surrounds the convective zone of the sun’s core.convective zone of the sun’s core.

Because the sun is made of gases, the Because the sun is made of gases, the term atmosphere refers to the uppermost term atmosphere refers to the uppermost region of solar gases. region of solar gases.

The sun’s atmosphere has three layers: The sun’s atmosphere has three layers: the photosphere, the chromosphere, and the photosphere, the chromosphere, and the corona.the corona.

The Sun’s AtmosphereThe Sun’s Atmosphere The photosphere is the visible surface of the The photosphere is the visible surface of the

sun.sun. Photosphere means “sphere of light.” Photosphere means “sphere of light.” The photosphere of the sun is the innermost The photosphere of the sun is the innermost

layer of the sun’s atmosphere.layer of the sun’s atmosphere. The photosphere is made of gases that have The photosphere is made of gases that have

risen from the convective zone. risen from the convective zone. The temperature in the photosphere is about The temperature in the photosphere is about

6,000ºC.6,000ºC. Much of the energy given off from the Much of the energy given off from the

photosphere is in the form of visible light.photosphere is in the form of visible light.

The Sun’s AtmosphereThe Sun’s Atmosphere The chromosphere is the thin layer of the sun The chromosphere is the thin layer of the sun

that is just above the photosphere and that that is just above the photosphere and that glows a reddish color during eclipses.glows a reddish color during eclipses.

The chromosphere lies just above the The chromosphere lies just above the photosphere. photosphere.

The chromosphere’s temperature ranges The chromosphere’s temperature ranges from 4,000°C to 50,000 °C.from 4,000°C to 50,000 °C.

The gases of the chromosphere move away The gases of the chromosphere move away from the photosphere, forming narrow jets of from the photosphere, forming narrow jets of hot gas that shoot outward and then fade hot gas that shoot outward and then fade away within a few minutes.away within a few minutes.

The Sun’s AtmosphereThe Sun’s Atmosphere

The corona is the outermost layer of the The corona is the outermost layer of the sun’s atmosphere.sun’s atmosphere.

The corona is a huge region of gas that has a The corona is a huge region of gas that has a temperature above 1,000,000ºC. temperature above 1,000,000ºC.

As the corona expands, electrons and As the corona expands, electrons and electrically charged particles called ions electrically charged particles called ions stream out into space.stream out into space.

These particles make up solar wind, which These particles make up solar wind, which flows outward from the sun to the rest of the flows outward from the sun to the rest of the solar system.solar system.

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