Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2 Doppler/ Sunspots/ Interior

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Doppler/

Sunspots/

Interior

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Lab notes

• “Sunspots” lab discussion today after class.• Telescope Lab next week.• Constellation Lab coming up.

• Picture• How to find it• Interesting objects• History/Mythology• Participation

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What is the speed of light?

A) 3x105

B) 3x108

C) Not enough information in A or B.

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The Doppler Effect

• One more tool…

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A source of light is approaching us at 3,000 km/s. All its waves are:

A) Red shifted by 1%

B) Blue shifted by 1%

C) Not affected, as c is constant in all reference frames.

D) Red shifted out of the visible into the infrared

E) Blue shifted out of the visible into the ultraviolet

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Figure 2.22Doppler Effect

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The Doppler Effect

• A “red” shift to longer wavelengths occurs when an object moves away from you.

• A “blue” shift to shorter wavelengths occurs when an object moves towards from you.

• Transverse velocities have no effect.

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The Doppler Effect

A Note on police radar• Pulses are emitted, and the

change in frequency of the echo pulse is what is measured - NOT a shift in the wavelength of the return pulse.

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Figure 2.23Doppler Shift

• For EM waves (astronomical purposes) wave speed = c• c = 3 x 108 m/s

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A source of light is approaching us at 3,000 km/s. All its waves are:

• Discuss what you think the effect will be on the spectral lines.

• Does frequency appear higher or lower?• By how much?

• Recall:

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A source of light is approaching us at 3,000 km/s. All its waves are:

A) Red shifted by 1%

B) Blue shifted by 1%

C) Not affected, as c is constant in all reference frames.

D) Red shifted out of the visible into the infrared

E) Blue shifted out of the visible into the ultraviolet

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A source of light is approaching us at 3,000 km/s. All its waves are:

A) Red shifted by 1%

B) Blue shifted by 1%

C) Not affected, as c is constant in all reference frames.

D) Red shifted out of the visible into the infrared

E) Blue shifted out of the visible into the ultraviolet

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Chapter 9

The Sun

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The temperature of the photosphere of the Sun is about:

A) 4500 K

B) 5800 K

C) 11000 K

D) 1 million K

E) 15 million K

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The temperature of the photosphere of the Sun is about:

A) 4500 K

B) 5800 K

C) 11000 K

D) 1 million K

E) 15 million K

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What is the meaning of the solar constant?

A) The regularity of the 11 year sunspot cycle.

B) The fact that features on the Sun appear to never change.

C) The stability of the Sun’s luminosity during its existence.

D) The amount of energy received at the Earth’s surface per unit area and unit time.

E) The fact that the amount of hydrogen turning into Helium in the core is fixed.

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What is the meaning of the solar constant?

A) The regularity of the 11 year sunspot cycle.

B) The fact that features on the Sun appear to never change.

C) The stability of the Sun’s luminosity during its existence.

D) The amount of energy received at the Earth’s surface per unit area and unit time.

E) The fact that the amount of hydrogen turning into Helium in the core is fixed.

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http://science.nasa.gov/science-news/science-at-nasa/2003/17jan_solcon/

http://www.nasa.gov/mission_pages/sdo/main/index.html

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Chapter 9

Sunspots

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Figure 9.15Sunspots

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Figure 9.16Sunspots, Up Close

• Darker (cooler) places on the Sun.

• Typically about the size of Earth (~10,000 km)

• Umbra - dark center (~4500K)

• Penumbra - lighter surrounding region (~5500 K)

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Sunspot Magnetism

• Zeeman effect - a slitting of spectral lines from magnetic fields. If you can measure the “splitting”, then you can determine the magnetic field.

• Magnetic field in sunspots • Typically ~1000x greater than that in the surrounding

region.• Field lines typically perpendicular to surface (either N or

S)• Magnetic field disrupts the convective flow. (Hot stuff in

the interior can’t “percolate” to the surface.)

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Sunspot Magnetism

• Sunspots typically occur in pairs• A N-S pair will follow each other in the

direction of the suns rotation.• Ordering (N-S or S-N) will be opposite

in northern and southern hemispheres.

• Direction reverses every 11 years.

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Figure 9.17Sunspot Magnetism

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Solar Rotation

• The sun rotates differentially• Equator – 25.1 days• 60° latitude - 30.8 days• Poles - 36 days• Interior - 26.9 days

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Figure 9.18Solar Rotation

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Solar Rotation

• Rope demonstration• Every 11 years, the polarity of the magnetic fields

reverse.• Number of sunspots follows this 11 year cycle.• Most recent maximum was in 2001.

• Solar Cycle - Two complete reversals of the magnetic field. Two sunspot cycles, or 22 years.

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Figure 9.19Sunspot Cycle

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Figure 9.20Maunder Minimum

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Active Regions

• Sites of explosive events on the photosphere.• Most associated with sunspots (magnetic fields)

• Prominences - loops or sheets of glowing gas ejected from an active region.

• Flares - more violent; may cause pressure waves• Coronal Mass Ejection - “bubbles” of ionized gas that

separate and escape from the corona. If these hit Earth, they disrupt Earth’s magnetic field.

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Figure 9.21Solar Prominences - ionized gas follows field lines

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Figure 9.22Solar Flare - more violent; may cause pressure waves

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Figure 9.23Coronal Mass Ejection - view from SOHO (Solar and Heliospheric Observatory.)

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As the Sun rotates, an individual sunspot can be tracked across its face.

From Eastern to Western limb, this takes about:A) 12 hours

B) A week

C) Two weeks

D) A month

E) 5.5 years

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As the Sun rotates, an individual sunspot can be tracked across its face.

From Eastern to Western limb, this takes about:A) 12 hours

B) A week

C) Two weeks

D) A month

E) 5.5 years

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Solar Interior/

Nuclear Fusion

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What about the internal structure?

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Solar Composition

Element

Number Percent

Mass Percent

H 91.2 71

He 8.7 27.1

O 0.078 0.97

C 0.043 0.4

N 0.0088 0.096

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Figure 9.2Solar Structure

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What about the internal structure?

• Core - • temperatures hot enough for nuclear reactions

• Radiation Zone - • Temperatures cooler, so no nuclear reactions.• Hot enough so everything is ionized. • Atoms can’t absorb photons.

• Convection Zone - • Temperature cooler. • Atoms form and can absorb radiation.

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Figure 9.6Solar Interior

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How do we know what is inside the Sun?

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How do we know what is inside the Sun?

Standard model

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Figure 9.4Stellar Balance

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Figure 9.5Solar Oscillations

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Figure 9.7Solar Convection

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Figure 9.8Solar Granulation

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Figure 9.11Solar Spicules

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Typically, a granule in the photosphere of the sun is about the size of?

A) A city, ~20-30 kilometers across.

B) Texas, ~1000 km across.

C) The Earth, ~12,000 km across.

D) Jupiter, ~100,000 km across.

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Typically, a granule in the photosphere of the sun is about the size of?

A) A city, ~20-30 kilometers across.

B) Texas, ~1000 km across.

C) The Earth, ~12,000 km across.

D) Jupiter, ~100,000 km across.

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From inside out, which is the correct order?

A) core, convective zone, radiative zone

B) photosphere, radiative zone, corona

C) radiative zone, convective zone, chromosphere

D) core, chromosphere, photosphere

E) convective zone, radiative zone, granulation

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From inside out, which is the correct order?

A) core, convective zone, radiative zone

B) photosphere, radiative zone, corona

C) radiative zone, convective zone, chromosphere

D) core, chromosphere, photosphere

E) convective zone, radiative zone, granulation

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Three Minute Paper

• Write 1-3 sentences.• What was the most important thing

you learned today?• What questions do you still have

about today’s topics?