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Guiding Questions. What is the source of the Sun’s energy? What is the internal structure of the Sun? How can we measure the properties of the Sun’s interior? How can we be sure that thermonuclear reactions are happening in the Sun’s core? Does the Sun have a solid surface?

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Guiding questions l.jpg
Guiding Questions

  • What is the source of the Sun’s energy?

  • What is the internal structure of the Sun?

  • How can we measure the properties of the Sun’s interior?

  • How can we be sure that thermonuclear reactions are happening in the Sun’s core?

  • Does the Sun have a solid surface?

  • Since the Sun is so bright, how is it possible to see its dim outer atmosphere?

  • Where does the solar wind come from?

  • What are sunspots? Why do they appear dark?

  • What is the connection between sunspots and the Sun’s magnetic field?

  • What causes eruptions in the Sun’s atmosphere?


The sun s energy is generated by thermonuclear reactions in its core l.jpg

The Sun’s luminosity (power output) is

L = 3.9 x 1026 watts (or joules per second)

The Sun is powered by thermonuclear fusion reactions in the core, where hydrogen is converted into helium, releasing energy in a process called the proton-proton-chain.

Einstein’s equation, E = mc2 describes how much energy, E, can be created from an amount of mass, m.

The Sun’s energy is generated by thermonuclear reactions in its core.


Thermonuclear reactions in the sun s core turn mass into energy l.jpg
Thermonuclear reactions in the Sun’s core turn mass into energy.

At extremely high temperatures and pressures,

4 Hydrogen atoms can combine to make 1 Helium atom

and release energy by E = mc2

4H  He + energy

HYDROGEN FUSION


A theoretical model of the sun shows how energy gets from its center to its surface l.jpg
A theoretical model of the Sun shows how energy gets from its center to its surface.

Thermonuclear fusion can only occur at very high temperatures and pressures.


Solar energy flows from the 1 core 2 radiative zone 3 convective zone l.jpg
Solar energy flows from the its center to its surface.(1) core(2) radiative zone(3) convective zone


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Astronomers probe the solar interior using the Sun’s own vibrations.

Sections of the Sun’s surface quickly oscillate up on down.


The sun s surface vibrations reveal its internal structure and motions l.jpg
The Sun’s surface vibrations reveal its internal structure and motions.

  • Exploring the Sun’s interior by studying its vibrations is called HELIOSEISMOLOGY.

  • Because we can not actually “see” inside the Sun, helioseismology provides theoreticians with a way to check to be sure their models of the solar interior are correct.


Neutrinos provide information about the sun s core and have surprises of their own l.jpg
Neutrinos provide information about the Sun’s core - and have surprises of their own.

  • Current models of the solar interior predict that 1038 neutrinos should be released every second by solar fusion.

  • Neutrino (n) detectors on Earth measure captures by cleaning fluid:

    Cl + n Ar + e-

    n + n p + e-

  • MYSTERY: Only 1/3 of the expected neutrinos from the Sun are being detected.

  • Solution to this “solar neutrino problem”: neutrinos have mass, so they change identity enroute!


Outer layers of the sun s atmosphere l.jpg
Outer Layers of the Sun’s Atmosphere have surprises of their own.

  • Photosphere - the 5800 K “surface” we see.

  • Chromosphere - the lower solar atmosphere, which rises to 25,000 K

  • Corona - the very thin outer atmosphere at millions of degrees (T>106 K)




The chromosphere is characterized by spikes of rising gas l.jpg
The chromosphere is characterized by spikes of rising gas. Sun’s atmosphere.

  • The chromosphere is the thin, pinkish layer of SPICULES just above the photosphere.

  • Spectrum is dominated by Ha emission lines, suggesting it is quite tenuous.

  • MYSTERY: The temperature is rises with height about the solar surface, though we would expect it to cool with increasing distance from the source!

  • Solution = solar magnetic fields


The corona ejects mass into space to form the solar wind l.jpg

Most easily seen during an eclipse. Sun’s atmosphere.

Thin gas at millions of degrees

The outflow of mass from the Sun is called the solar wind.

The corona ejects mass into space to form the solar wind.


Slide23 l.jpg

Magnetic fields cause structure, heating, and energy outbursts from the Sun’s atmosphere.

Sunspots

Hot atmosphere

Flares and mass ejections

Solar cycle

Temperature changes on Earth


Slide24 l.jpg

Sunspots are low-temperature regions in the photosphere. outbursts from the Sun’s atmosphere.


The daily movement of sunspots reveals that the sun s rotation takes about 4 weeks l.jpg
The daily movement of outbursts from the Sun’s atmosphere.sunspots reveals that the Sun’s rotation takes about 4 weeks.


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The cyclical change in the latitude of sunspots also reveals that the Sun experiences an 11-year solar cycle.


Extreme peaks or absences of sunspots may change earth s climate l.jpg
Extreme peaks or absences of sunspots may change Earth’s climate

Maunder Minimum ~ 1650

  • Few sunspots

  • Colder climate

  • Famine in Europe

  • Thames froze

Mideval Maximum ~ 1100

  • Many sunspots

  • Hotter climate

  • Famine in N. America

  • Ancient Pueblo people abandoned Chaco canyon

  • Icemelt permitted Vikings to reach N. America


Sunspots are produced by a 22 year cycle in the sun s magnetic field l.jpg
Sunspots are produced by a 22-year cycle in the Sun’s magnetic field.

  • Charged particles, such as electrons, will move along magnetic field lines.

  • The Sun’s positive pole is in the North for 11 years, then switches to the South for 11 years



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The sunspot cycle is partly due to the Sun’s differential rotation. This helps solar magnetic fields twist up, intensify, emerge, cancel, then repeat the cycle.


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The interior of the Sun rotates at slower than the equator and faster than the poles.

The radiative zone seems to rotate as a rigid sphere.


The sun s magnetic field also produces other forms of solar activity l.jpg
The Sun’s magnetic field also produces other forms of solar activity.

  • The highly charged gases in the Sun’s outer atmosphere, follow loops in the Sun’s magnetic field.


Solar magnetic fields create plages and filaments prominences l.jpg
Solar magnetic fields create solar activity.plages and filaments / prominences.




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The Sun’s magnetic field affects all life on Earth, service

not just cell phone users.


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Guiding Questions service

  • What is the source of the Sun’s energy?

  • What is the internal structure of the Sun?

  • How can we measure the properties of the Sun’s interior?

  • How can we be sure that thermonuclear reactions are happening in the Sun’s core?

  • Does the Sun have a solid surface?

  • Since the Sun is so bright, how is it possible to see its dim outer atmosphere?

  • Where does the solar wind come from?

  • What are sunspots? Why do they appear dark?

  • What is the connection between sunspots and the Sun’s magnetic field?

  • What causes eruptions in the Sun’s atmosphere?


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