Chapter 29.1 Structure of the Sun

Std 1e: Students know the Sun is a typical star and is powered by nuclear reactions, primarily the fusion of hydrogen to form helium.

Objective 1: Explain how the sun converts matter into energy in its core

Objective 2: Compare the radiative and convective zones of the sun

Objective 3: Describe the 3 layers of the sun’s atmosphere

The Sun’s Energy

• 300,000x larger than Earth

• Spectrograph – a device used to break up the sun’s light into a spectrum– Used to determine

the amount of elements in the Sun

• Composition of the Sun –Both Hydrogen and Helium occur in the sun –75% of sun’s mass is hydrogen –Hydrogen and helium together make up

99% of the sun’s mass

Nuclear Fusion

• Nuclear fusion - the process by which nuclei of small atoms combine to form a new more massive nucleus

• Fusion releases huge amounts of energy and has 3 steps: *each step releases energy

• Step 1) Two hydrogen nuclei (or protons) collide and fuse.

• One proton will become a neutron (release of positron)• It is a proton-neutron pair

• Step 2) Another proton combines w/ the pair making a 2 proton 1 neutron nucleus

• Step 3) Two of these nuclei (2 pro 1 neu) collide and fuse. • 2 protons are released. • The remaining 2 protons and 2 neutrons fuse

forming a helium nucleus

The Final Product

• Nuclear fusion of 2 hydrogen nuclei combines to produce a helium nucleus

• The helium nucleus is only 0.7% mass of the hydrogen nucleus from which it formed

• The lost mass is converted into energy, which causes the sun to shine and it’s high temperature

Mass Changing in Energy

• The sun’s energy comes from nuclear fusion • The mass lost during fusion becomes energy–Subatomic particles are released = Neutrinos

• Einstein’s equation (E=mc2) can be used to calculate how mass (or matter) can be converted into energy– E = energy produced– m = mass or amount of matter– c = speed of light (3,000,000km/s)

• Astronomers used this equation to explain the huge quantities of energy produced by the sun

Objective 1: Explain how the sun converts matter into energy in its core

• What provides the sun with its energy?– Nuclear fusion

• What 2 elements make up the sun’s mass?– Hydrogen and helium

• In the equations E = mc2, what does the c represent?– Speed of light (3,000,000 km/s)

The Sun’s Interior

• Has 3 parts:–1) The Core –2) The Radiative

Zone –3) The

Convection Zone

1] The Core

• The center of the sun, it’s 25% of sun’s diameter

• Temp = 15,000,000 °C –

• Converts matter into energy!

2] The Radiative Zone

• The layer surrounding the core • Temps range from 2,000,000-7,000,000 °C. • Energy moves outward in the form of

electromagnetic waves, or radiation

3] The Convection Zone

•Surrounding the Radiative Zone•About 2,000,000 °C. •Energy in this zone moves by convection •As gases move outward from this zone it losses energy, becomes more dense and sinks – Therefore, energy is

transferred

Objective 2: Compare the radiative and convective zones of the sun

• What are the 3 parts of the sun’s interior?– Core, convection zone, and radiative zone

• What is the temperature of the core?– 15,000,000 °C

• How does energy move in the radiative zone?– Electromagnetic waves (radiation)

• What surrounds the radiative zone?– Convection zone

The Sun’s Atmosphere

• Surrounding the Convection Zone is the sun’s atmosphere (the uppermost region of solar gases) – The 3 layers are:• 1) Photosphere• 2) Chromosphere • 3) Corona

1] The Photosphere

• The innermost layer• Made of gases that

have risen from the convection zone

• Much of the energy given off is in the form of visible light, this light is seen from Earth

2] Chromosphere (above the photosphere)

• A thin layer of gases • From 4,000-50,000 °C. • The gases move away

from the photosphere forming narrow jets of hot gas that shoot outward

3] The Corona (outermost layer of

the atmosphere)

• Solar Wind - has a strong magnetic field, electrons and electrically charged particles stream out into space

*The chromosphere and the corona can only be seen from Earth during a solar eclipse

Objective 3: Describe the 3 layers of the sun’s atmosphere

• What are the 3 layers of the atmosphere?– Photosphere, chromosphere and corona

• What is the innermost layer?– Photosphere

• What is the layer above the photosphere?– Chromosphere

• What has a strong electromagnetic field and electrically charged particles stream into space?– Solar winds