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Chapter 14Our Star

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Why does the Sun Shine?

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Is it on FIRE?

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Is it on FIRE?

Luminosity~ 10,000 years

Chemical energy content

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Is it on FIRE? …NO!

Luminosity~ 10,000 years

Chemical energy content

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Is it CONTRACTING?

Insert TCP 6e Chapter 14 opener

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Is it CONTRACTING?

Luminosity

Gravitational potential energy~ 25 million years

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Is it CONTRACTING?...NO!

Luminosity

Gravitational potential energy~ 25 million years

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Why does the Sun shine?

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Weight of upper layers compresses lower layers.

Insert TCP 6e Figure 14.1

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Gravitational equilibrium:

There is a balance between the outward fusion pressure and the inward pressure, due to gravity.

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What is the Sun’s structure?

Insert TCP 6e Figure 14.3

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Solar wind:

A flow of charged particles from the surface of the Sun

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Corona:

Outermost layer of solar atmosphere and seen only during a total solar eclipse.

~1 million K

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Chromosphere:

Middle layer of solar atmosphere and seen only during a total solar eclipse.

~ 104–105 K

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Photosphere:

Visible surface of Sun

~ 6000 K

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Convection Zone:

Energy transported upward by rising hot gas

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Radiation Zone:

Energy transported upward by photons

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Core:

Energy generated by nuclear fusion

~ 15 million K

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Clicker QuestionWhat is the surface we see?

A. coronaB. photosphereC. chromosphereD. solar wind

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Clicker QuestionWhat is the surface we see?

A. coronaB. photosphereC. chromosphereD. solar wind

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Clicker QuestionWhat layer is the hottest?

A. coronaB. photosphereC. chromosphere

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Clicker QuestionWhat layer is the hottest?

A. coronaB. photosphereC. chromosphere

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Clicker QuestionWhat layer is the coolest?

A. coronaB. photosphereC. chromosphere

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Clicker QuestionWhat layer is the coolest?

A. coronaB. photosphereC. chromosphere

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How does nuclear fusion occur in the Sun?

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Fission

Big nucleus splits into smaller pieces.

(Example: nuclear power plants)

Fusion

Small nuclei stick together to make a bigger one.

(Example: the Sun, stars)

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High temperatures enable nuclear fusion to happen in the core.

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The Sun releases energy by fusing four hydrogen nuclei into one helium nucleus.

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The proton–proton chain is how hydrogen fuses into helium in Sun.

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IN4 protons

OUT4He nucleus

2 gamma rays2 positrons2 neutrinos

Total mass is 0.7% lower.

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Proton-Proton Chain in Gory Detail

Step 1: 1H1 + 1H1 --> 2H1 + e+ + 1H1 is a hydrogen nucleus - subscript is the number of protons

in nucleus, superscript is the number of protons + neutrons in the nucleus. Hydrogen nucleus has 1 proton, 0 neutrons.

2H1 is a deuterium nucleus (hydrogen isotope) with 1 proton and 1 neutron in nucleus.

e+ is a positron or antiparticle of the e-. When e+ and e- meet,

e+ + e- __ > 2 two gamma rays are producedis a neutrino and helps to carry away energy.

Step 2: 1H1 + 2H1--> 3He2 +

3He2 is a helium isotope, is a gamma ray.

Step 3: 3He2 + 3He2 --> 4He2 + 1H1 + 1H1 4He2 is ordinary or ‘balloon’ helium.

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Clicker QuestionWhat is e+?

A. electronB. positronC. NeutronD. protonE. neutrino

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Clicker QuestionWhat is e+?

A. electronB. positronC. NeutronD. protonE. neutrino

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Clicker QuestionWhat is 2H1?

A. gamma rayB. helium nucleusC. deuterium nucleusD. ordinary hydrogen nucleus

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Clicker QuestionWhat is 2H1?

A. gamma rayB. helium nucleusC. deuterium nucleusD. ordinary hydrogen nucleus

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Clicker QuestionWhat is ?

A. gamma rayB. positronC. NeutronD. protonE. neutrino

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Clicker QuestionWhat is ?

A. gamma rayB. positronC. NeutronD. protonE. neutrino

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Clicker QuestionWhat is ?

A. gamma rayB. positronC. NeutronD. protonE. neutrino

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Clicker QuestionWhat is ?

A. gamma rayB. positronC. NeutronD. protonE. neutrino