Charles Hakes Fort Lewis College1

Charles Hakes Fort Lewis College2 Chapter 9 The Sun

Charles Hakes Fort Lewis College3 Outline If you received a C- or below for your mid-term grade, please come by my office to discuss your situation. The Sun Solar atmosphere Sunspots Next time finish chapter 9

Charles Hakes Fort Lewis College4 Tutoring Tues, Wed, Thurs after 5:00 ????

Charles Hakes Fort Lewis College5 The temperature of the photosphere of the Sun is about: A) 4500 K B) 5800 K C) K D) 1 million K E) 15 million K

Charles Hakes Fort Lewis College6 The temperature of the photosphere of the Sun is about: A) 4500 K B) 5800 K C) K D) 1 million K E) 15 million K

Charles Hakes Fort Lewis College7 Chapter 9 The Sun

Charles Hakes Fort Lewis College8 Figure 9.1 The Sun Solar Properties Radius696,000 km Mass1.99x10 30 kg Ave. Density1410 kg/m 3 Rotation25.1 d (eq) 30.8 d (60°) 36 d (pole) Surface Temp5780 K Luminosity3.86x10 26 W

Charles Hakes Fort Lewis College9 How do you determine these properties? Solar Properties Radius696,000 km Mass1.99x10 30 kg Ave. Density1410 kg/m 3 Rotation25.1 d (eq) 30.8 d (60°) 36 d (pole) Surface Temp5780 K Luminosity3.86x10 26 W

Charles Hakes Fort Lewis College10 How do you determine these properties? Radius - Mass - Average Density - Rotation Period - Surface Temperature - Luminosity -

Charles Hakes Fort Lewis College11 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Average Density - Rotation Period - Surface Temperature - Luminosity -

Charles Hakes Fort Lewis College12 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Rotation Period - Surface Temperature - Luminosity -

Charles Hakes Fort Lewis College13 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Calculate from mass and radius Rotation Period - Surface Temperature - Luminosity -

Charles Hakes Fort Lewis College14 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Calculate from mass and radius Rotation Period - Sunspots Surface Temperature - Luminosity -

Charles Hakes Fort Lewis College15 How could you determine the temperature of the photosphere of the Sun? A) only direct spacecraft measurement B) Newton’s Law C) Stefan’s Law D) Wein’s law

Charles Hakes Fort Lewis College16 How could you determine the temperature of the photosphere of the Sun? A) only direct spacecraft measurement B) Newton’s Law C) Stefan’s Law D) Wein’s law

Charles Hakes Fort Lewis College17 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Calculate from mass and radius Rotation Period - Sunspots Surface Temperature - Wein’s Law Luminosity -

Charles Hakes Fort Lewis College18 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Calculate from mass and radius Rotation Period - Sunspots Surface Temperature - Wein’s Law Luminosity - Stefan’s Law and area of Sun

Charles Hakes Fort Lewis College19 Figure 9.3 Solar Luminosity Solar Constant is the energy reaching the Earth above the atmosphere ~1400 W/m 2

Charles Hakes Fort Lewis College20 How do you determine these properties? Radius - baseline = angle x distance distance from Kepler’s Laws/radar Mass - Newton’s Law of gravitation Average Density - Calculate from mass and radius Rotation Period - Sunspots Surface Temperature - Wein’s Law Luminosity - Stefan’s Law and area of Sun Measure solar constant and multiply by area at 1 AU.

Charles Hakes Fort Lewis College21 What about the atmosphere? Photosphere - What we see. (~5780 K) Chromosphere - pinkish color (from H  line); can see during eclipse. cooler temperature (~4500 K) Transition zone/Corona - Shift from absorption spectrum to emission spectrum Corona very hot (~3 million K) Solar Wind - The Sun is evaporating!

Charles Hakes Fort Lewis College22 Figure 9.10 Solar Chromosphere

Charles Hakes Fort Lewis College23 Figure 9.12 Solar Corona

Charles Hakes Fort Lewis College24 Figure 9.24 Active Corona

Charles Hakes Fort Lewis College25 Figure 9.13 Solar Atmospheric Temperature

Charles Hakes Fort Lewis College26 Chapter 9 Sunspots

Charles Hakes Fort Lewis College27 Figure 9.15 Sunspots

Charles Hakes Fort Lewis College28 Figure 9.16 Sunspots, 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)

Charles Hakes Fort Lewis College29 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.)

Charles Hakes Fort Lewis College30 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.

Charles Hakes Fort Lewis College31 Figure 9.17 Sunspot Magnetism

Charles Hakes Fort Lewis College32 Solar Rotation The sun rotates differentially Equator – 25.1 days 60° latitude days Poles - 36 days Interior days

Charles Hakes Fort Lewis College33 Figure 9.18 Solar Rotation

Charles Hakes Fort Lewis College34 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 Solar Cycle - Two complete reversals of the magnetic field. Two sunspot cycles, or 22 years.

Charles Hakes Fort Lewis College35 Figure 9.19 Sunspot Cycle

Charles Hakes Fort Lewis College36 Figure 9.20 Maunder Minimum

Charles Hakes Fort Lewis College37 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.

Charles Hakes Fort Lewis College38 Figure 9.21 Solar Prominences - ionized gas follows field lines

Charles Hakes Fort Lewis College39 Figure 9.22 Solar Flare - more violent; may cause pressure waves

Charles Hakes Fort Lewis College40 Figure 9.23 Coronal Mass Ejection - view from SOHO (Solar and Heliospheric Observatory.)

Charles Hakes Fort Lewis College41 l field trip

Charles Hakes Fort Lewis College42 The Doppler Effect …is that waves moving toward you are (observed) at a higher frequency than waves moving away from you (observed at a lower frequency). When objects are moving sideways there will be no dopper effect.

Charles Hakes Fort Lewis College43 Figure 2.23 Doppler Shift For EM waves (astronomical purposes) wave speed = c c = 3 x 10 8 m/s

Charles Hakes Fort Lewis College44 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:

Charles Hakes Fort Lewis College45 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

Charles Hakes Fort Lewis College46 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

Charles Hakes Fort Lewis College47 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.

Charles Hakes Fort Lewis College48 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.

Charles Hakes Fort Lewis College49 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?