i.the solar spectrum : sun’s composition and surface temperature ii.sun’s interior: energy...

I. The Solar Spectrum: Sun’s composition and surface temperature

II. Sun’s Interior: Energy source, energy transport, structure, helioseismology.

III. Sun’s Atmosphere: Photosphere, chromosphere, corona

IV. Solar Activity: Sunspots, solar magnetism, solar cycle, prominences and flares.

Outline of The Sun (Ch. 10)(Not exactly like the book)

I. Solar Spectrum: Composition and Surface Temperature

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I. Solar Spectrum: How do we know the composition of the Sun?

I. Solar Spectrum: How do we know the composition of the Sun?

What type of Spectrum is this?

How do we know this?

Surface Temperature: approximately 6,000 K





Outline of The Sun (Ch. 10)

What is the source of the Sun’s energy?

a) Chemical reactions

b) Gravitational contraction

c) Nuclear fission (like in nuclear power plants)

d) Nuclear fusion

Question 1

Why does the Sun shine?

Is it on FIRE?

Fuel

Rate of burning that fuel

Is it on FIRE?

Luminosity~ 10,000 years

Chemical Energy Content

Is it on FIRE? … NO!

Luminosity~ 10,000 years

Chemical Energy Content

Is it CONTRACTING?

Luminosity

Gravitational Potential Energy

Is it CONTRACTING?

~ 25 million years

Luminosity

Gravitational Potential Energy

Is it CONTRACTING? … NO!

~ 25 million years

E = mc2

- Einstein, 1905

Is it powered by NUCLEAR ENERGY?

Luminosity~ 10 billion years

Nuclear Potential Energy (core)

Is it powered by NUCLEAR ENERGY? … YES!

Luminosity~ 10 billion years

Nuclear Potential Energy (core)

What is the source of the Sun’s energy?

a) Chemical reactions b) Gravitational contraction c) Nuclear fission (like in nuclear

power plants) d) Nuclear fusion

Question 1

Fission

Big nucleus splits into smaller pieces

(Nuclear power plants)

Fusion

Small nuclei stick together to make a bigger one

(Sun, stars)

4 protons one Helium nucleus + Energy

Hydrogen Fusion into Helium in the Sun’s Core

4 protons one helium nucleus + Energy

The mass of the four protons is higher than that of the helium nucleus where did the missing mass go?


4 protons one helium nucleus + Energy

The mass of the four protons is higher than that of the helium nucleus where did the missing mass go?

The mass became energy, and E=mc2 so a little mass can produce a lot of energy


Proton-proton chain is how hydrogen fuses into helium in Sun

• Sun’s interior

Core:

Energy generated by nuclear fusion

Radiation Zone:

Energy transported upward by photons

Convection Zone:

Energy transported upward by rising hot gas

In the Sun, gravity is balanced by outward pressure (due to the outflow of energy)

Solar Thermostat

Temperature Restored

Temperature Decreases

Fusion Rate Decreases

Core compresses

Solar Thermostat

Temperature Restored

Temperature Increases

Fusion Rate Increases

Core expands

Helioseismology

By studying the motion of the Sun’s surface we can learn about its interior in a similar way to the study of Earthquakes.

What have we learned? How does the solar thermostat work? There is a equilibrium between gravity

and energy outflow……. How does the energy from fusion get

out of the Sun? Energy is produces in the core by nuclear

fusion and it gets radiated outward. The convection zone carries energy the rest of the way to the photosphere, where it is radiated into space as sunlight.

How do we know what is happening inside the Sun?

Helioseismology and other techniques

Photosphere:

Visible surface of Sun

T ~ 6,000 K

Chromosphere:

Middle layer of solar atmosphere

Corona:

Outermost layer of solar atmosphere

Solar Granulation in the Photosphere

Convection (rising hot gas) takes energy to surface

Cloud tops on Earth produced by convection: warm air rises

Sunspots

Why do sunspots look dark? a) They are dark clouds b) They are smoke from the Sun’s

interior c) They are cooler than the rest of

the Sun’s surface d) None of the above

Question

Why do sunspots look dark? a) They are dark clouds b) They are smoke from the Sun’s

interior c) They are cooler than the rest

of the Sun’s surface d) None of the above

Question

Loops trace magnetic field lines

Blackbody radiation:

The hotter the brighter

The hotter the bluer

Why do sunspots look dark? They are cooler than the rest of

the Sun’s surface Are they redder?

Review from Ch 5

Sunspots

Visible during a total solar eclipse

Solar Chromosphere

Solar Chromosphere

Visible during a total solar eclipse

Solar Corona

Coronal mass ejections send bursts of energetic charged particles out through the solar system

I. Sunspots: main indicator

II. Prominences and flares: also indicators of solar activity

III. Solar cycle: 11-year cycle

IV. Solar Activity

Charged particles streaming from Sun can disrupt electrical power grid and can disable communications satellites

Energetic particles high in Earth’s atmosphere cause auroras (aka Northern Lights)

How does solar activity affect humans?

Bursts of charged particles ejected from the Sun during periods of high solar activity can hamper radio communications,disrupt electrical power generation,and damage orbiting satellites.

Solar activity can also have a strong impact on Earth’s weather

Sunspot numbers and temperature on Earth: During the mid-to-late 1600s records indicate

a very cold period on Earth

i.the solar spectrum : sun’s composition and surface temperature ii.sun’s interior: energy...

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