Introduction to Solar System 1

7/28/2019 Introduction to Solar System 1

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18-Apr-13

IESO

Introduction to Solar System

Part 1


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The Sun: Our

Extraordinary OrdinaryStar


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Filaments

Across the Sun


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Bulk Properties of the Sun

Diameter

Mass

Density

Rotation Periods

Surface Temp. Core Temp.

109 Earth Diameters

333,000 Earth Masses

1408 kg/m3

Equatorial: 25 Days

Polar: 35 Days

5800 K15,500,000 K


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Limb Darkening

The sun is not as bright near the limb as it is in the center. Also it is moreyellow, indicating that we are looking through cooler layers near the limbthan at the center.

This is because we see deeper into the photosphere when we look straightdown than when we look obliquely.

Mercury


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Explanation of Limb Darkening


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The Suns Atmosphere

The photosphere is the visible layer of the Sun.

The chromosphere is a mostly cooler layer that lies just abovethe photosphere. This region creates the Suns absorption linespectrum.

The transition region is a thin region above thechromosphere, where the temperature rises rapidly from about10,000 K to a million K.

The coronais the Suns outer atmosphere. The temperature ofthe corona is 1 to 2 million K. The corona extends severaltimes the diameter of the Sun.


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Photosphere

showing

Solar Granulation


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Solar Granulation

High-resolution

photographs of the

Suns surface reveal a

blotchy pattern, called

granulation. Granules,

which measure about1000 km across, are

convection cells in the

Suns photosphere.

Solar Granulation Video
http://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-2_GranulesSunspots.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-2_GranulesSunspots.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-2_GranulesSunspots.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.html


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Spicules and Supergranules in the Chromosphere

Supergranules are regions of rising and

falling gas, spanning hundreds of granules


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The Solar Corona


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The Active Sun

Sunspots and the Sunspot Cycle Solar Magnetism and the Solar Cycle

Other Atmospheric Phenomena Plages

Active Regions Prominences

Filaments

Coronal Holes

Flares

Coronal Mass Ejections


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Sunspots

Sunspots are typically about 10,000 km in diameterabout the size of theEarth. They have a dark central umbra surrounded by a grayish, structured

penumbra.

They appear dark only by comparison to the brighter surroundingphotosphere. They are cooler regions of the photosphere. The temperatureof the umbra is about 4500 K and that of the penumbra is about 5000 K.

A large group of sunspots typically lasts about 50 days.

Galileo determined the Suns rotation period by timing the movement ofsunspots. The Sun rotates in 25.4 days at the equator and in 33 days in the

polar region.

Motion of Sunspots Video
http://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-3_MotionSunspot.movhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-3_MotionSunspot.movhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.html


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The Sunspot Cycle


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Solar Magnetism

Sunspots are directly linked to intense magnetic fields on the Sun. Whenatoms are in magnetic fields, their spectrum lines are split into two or morelines on each side of the central line. This is called the Zeeman effect.

The strong magnetic field in sunspots lowers their temperature byinterfering with the convective flow of hot gas toward the surface.

Sunspots usually come in pairs with the magnetic field coming out of onemember of the pair and going in at the other member. In oppositehemispheres, sunspot pairs are reversed in their polarity.

Solar Cycle: The 11-year sunspot cycle is the solar cycle. In alternatesunspot cycles, the Suns magnetic field reverses direction causing the

polarity of the sunspots to reverse.


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Zeeman Splitting of Spectrum Lines


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Magnetic Field Lines and Sunspot Pairs


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Effect of Suns Differential Rotation on its Magnetic Field


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Other Atmospheric Phenomena

Plagesbrighter (hotter) areas in chromosphere

Filamentsdark streaks above the chromosphere. Huge volumes of gas

uplifted into the corona

Prominencesfilaments viewed from the side

Coronal Holesdarker (cooler) areas in corona, visible in X-rays,

where gases easily can escape from the Sun

Flaresviolent eruptive events seen in UV & X-rays

Coronal Mass Ejectionshuge, balloon-shaped volumes of high-energy gas being ejected


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Solar Prominences

Prominences and the Corona photographed during the

solar eclipse of July 11, 1991, near sunspot maximum


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23Active Sun in H


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24A Solar Prominence from SOHO


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25Prominences


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26X-ray picture of a Coronal Hole


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27UV picture of a Solar Flare


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28A Coronal Mass Ejection


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The Suns Composition

The main elements are hydrogen and helium, as in the gas giant planets andin other stars and nebulae in the universe.

Element by Atoms by Mass

Hydrogen, H 92% 74%

Helium, He 8% 25%

Others 0.1% 1%

This data is needed for the homework.


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Main Regions of the Sun


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The Suns Interior

The Standard Solar Model. Is a mathematical model of the Sun, made by

combining all available observations with theoretical insight into solarphysics. This model shows that the Suns interior has three major regions,listed from outside to inside.

Convection Zone. This zone extends downwards from the photosphereabout 200,000 km. The material is in constant convective motion.

Radiation Zone. Below the convection zone and extending to the core, isthe radiation zone, where energy is transported toward the surface byradiation rather than by convection.

Core. The central core, about 200,000 km in radius, is the site of thenuclear reactions that generate the Suns enormous energy output.


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Density & Temperature Profiles of the Suns Interior


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The Suns Source of Energy

Solar Constant is 1400 W/m2.

Luminosity of the Sun is 1400 W/m2 4 (1 AU)2 = 41026 W.

The Conversion of Mass to Energy: Mass and energy are related throughEinsteins equationE= mc2.

Solar Energy from Nuclear Fusion, the combining of light nuclei intoheavier ones. The sum of the masses of the light nuclei is a little greaterthan the mass of the heavier nucleus that is formed.

The Sun gets its energy from theProton-Proton Chain, fusing 4 hydrogen

atoms into 1 helium atom.


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The Proton-Proton Chain

Hydrogen to Helium Animation
http://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-1_HydrogenHelium.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-1_HydrogenHelium.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/10-1_HydrogenHelium.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_10/Animations/3-2_RefractingTelescope.html


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How Energy Gets from the Suns Core to

Its Surface part 1

Radiative Transfer.

In the central regions of the Sun, the temperature is so hot that all theelectrons are stripped from the nuclei. Thus there are no boundelectrons to move from one state to another, absorbing radiation.

This region is relatively transparent to radiation, allowing energy toflow out freely.

Radiation diffuses slowly outward in a haphazard zigzag pattern, takingabout 170,000 years on the average to go from the core to the bottom ofthe convective zone.


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How Energy Gets from the Suns Core to

Its Surface part 2

Convective Transfer. As the temperature drops outside the inner core,atoms can retain some electrons. This causes the gas to become more andmore opaque to radiation. The energy must still get out, but since theradiation is blocked, convection begins and carries the energy away to the

surface. This takes about 10 days to reach the photosphere. Convection Cells. In the deep solar interior they are thought to be large,

perhaps 30,000 km across. At higher levels the convection cells aresmaller, about 1000 km across just below the photosphere.


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Solar Neutrinos

Neutrinos are ghostly particles with no charge and having animmeasurably small mass.

They go through matter like it isnt there. Therefore they are

very difficult to detect.

Solar neutrinos are going from the Sun through the Earth and

through your body right nowroughly 100 billion of them per

square centimeter each second.

H li i l


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Helioseismology

Sound wavesresonating within thesolar interior cause the

photosphere to move inand out, rhythmicallydistorting the shape ofthe Sun. This heavingmotion can bedescribed as thesuperposition of millionsof oscillations, like theone shown here.

Sound waves inside theSun, like seismic waves

in the Earth, arerefracted back out. TheSuns surface reflects

waves back in. Howdeep a wave penetrates,and how far around theSun it goes before it hitsthe surface depends on

its wavelength.

Rising Gasses

Descending Gasses


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Summary of Key Ideas

Know and Understand: The size of the Sun compared with Earth and its

surface temperature

The regions of the Suns atmosphere

The nature of sunspots and the sunspot cycle

Where and how the Sun gets its energy

The regions of the Suns Interior

Documents

Introduction to Solar System 1