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The Sun


The Sun Our Star Think About This! What would happen if the sun s temperature increased? How might the physical environment change? Would it change the way we live? – PowerPoint PPT presentation

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Title: The Sun

The Sun
  • Our Star

Think About This!
  • What would happen if the suns temperature
  • How might the physical environment change?
  • Would it change the way we live?
  • What would happen if the suns temperature

Energy from the Sun
  • Enormous energy results from the fusion of
    Hydrogen nuclei into Helium nuclei in its core.
  • Einsteins Theory
  • Emc2
  • E energy
  • m mass
  • c speed of light

Energy from the Sun
  • The energy produced moves outward through the
    distinct gaseous layers of the inner zone of the
    sun and through the atmosphere.
  • Think of this one square inch of the suns
    surface gives off heat that would be the same as
    300,000 burning candles crammed into that square

Whats the Sun made of?
  • It contains most of the known elements
  • 71 hydrogen
  • 27 helium

The Structure of the Sun
Measuring the Suns Properties
  • Distance originally measured by triangulation,
    now we use radar
  • We can determine the radius once we know the
    distance by using angular size
  • We can calculate the mass from Keplers Third Law
  • Surface gravity 30 X that of Earth
  • Radiates a total of 4 X 1026 watts of power into
    space energy that is replaced by the nuclear
    fusion of hydrogen into helium in the core
  • Gaseous throughout

The Solar Interior
  • Our view inside is obscured by a dense layer of
    gas below the surface
  • This layer is called the photosphere (it is what
    we see)
  • The photosphere helps the sun retain heat and
    reduces the amount of fuel that must be consumed

The Solar Interior
  • Density and Temperature rise steadily as we move
  • Near the core the density is 100 X greater than
    that of water
  • Still remains gaseous throughout because the heat
    doesnt allow the atoms to bond
  • Photosphere temperature 5780 K
  • Core 15 million K

Energy Transport
  • Moves from the core to the surface (hot to cold)
  • Near the core energy is transported by radiation
  • Zone is called the Radiative Zone
  • It takes 1 million years for a photon of energy
    to move from the core to the surface of the sun

Energy Transport
  • Next zone moving outward is the Convective Zone
  • Gases rise and sink as they are heated and cooled
    creating convection currents
  • This rising and falling creates a pattern called
  • Using the Doppler Effect scientists have
    determined that the gas bubbles rising are
    traveling at 100s of km/s

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The Solar Atmosphere
  • The solar atmosphere is composed of low density
    gases that lie just above the photosphere
  • Immediately above the photosphere the temperature
    decreases and then increases to several million K
    as we increase altitude
  • Scientists arent sure why this happens, but
    speculate that gravity may play a role

The Solar Atmosphere
  • Chromosphere is the first layer of the solar
  • Can only be seen during a total eclipse seen as
    a thin red zone
  • Contains thin columns called spicules which are
    jets of hot gas
  • Color comes from the strong emission line of
  • Temperature ranges from 4500 K to 50,000 K at an
    altitude of 2000 kilometers

The Solar Atmosphere
  • Corona is the outermost layer of the suns
    atmosphere that blends into space
  • Temperatures reach 1 million K
  • Such low density gas that we usually look right
    through it
  • Can only be seen during a total eclipse
  • Has huge regions of cooler gas called coronal
  • Contains very little energy despite the high

How does the Sun work?
  • Hydrostatic equilibrium the rapid motion of the
    atoms creates pressure that gives an outward push
    that creates a balance between the inward pull of
    gravity keeping the sun from collapsing under its
    tremendous gravity
  • The sun is powered by nuclear fusion

How does the Sun work?
  • From Einsteins Theory
  • E mc2
  • a 1 gram mass (about the size of an aspirin)
    produces 9 X 1013 joules of energy which is
    equivalent to 20 kilotons of TNT (the same as a
    small nuclear weapon)

Hydrogen Fusion
  • 2 hydrogen protons collide with each other and
  • One proton changes to a neutron (green) and an
    electron is given off
  • Results is a nucleus with one proton and one

Step 2
Hydrogen Fusion
  • We will call this step 3
  • Another proton combines with the proton/neutron
  • Gamma rays (energy) given off
  • Nucleus now contains 2 protons and 1 neutron

Hydrogen Fusion
  • We will call these steps 4 and 5
  • Two - 2proton/1neutron nuclei collide and fuse
    giving 4p2n (Step 4)
  • Two protons are thrown off giving nucleus with
    2 protons and 2 neutrons (helium) (Step 5)

Step 5
Mass into Energy
  • Einstein and his theory of relativity 1905
  • Showed how a large amount of energy can be
    created from a very small amount of matter
  • Think of this The sun converts 600,000,000 tons
    of hydrogen into Helium every second.
  • How much hydrogen is converted every day?

How much energy is given off? We can do the
  • 4 hydrogen to make the Helium atom
  • Mass of 4 hydrogen 6.693 X 10-27 kg
  • Mass of 1 helium 6.645 X 10-27 kg
  • Mass lost 0.048 X 10-27 kg
  • Plugging this into E mc2
  • E 0.048 X 10-27 kg X (3 X 108m/s)2
  • E 4.3 X 10-12 joules per atom

We can do the calculations
  • This number seems small be when we consider that
    600,000,000 tons of hydrogen are converted into
    helium every second we can see the tremendous
    amount of energy that is produced every second
  • The total energy released is equivalent to 100
    million megaton H-bombs exploding per second

Probing the Suns Core
  • Solar Nutrinos particles released during
    hydrogen fusion they dont have a charge or any
    mass which gives them tremendous penetrating
  • Roughly a trillion nutrinos pass through your
    body every second
  • They penetrate through the earth and keep on
  • 4 nutrino detectors located worldwide deep

Nutrino Detector
Solar Seismology
  • Waves like earthquakes pass through the sun
  • We can use a Doppler shift and computer models to
    predict how the observed surface waves are
    affected by conditions in the Suns deep
    interior. (Called helioseismology)

Solar Magnetic Activity
  • Many features we see on the surface of the Sun
    are caused by its magnetic field
  • Sunspots the most common of the magnetic
    phenomena appear as large dark-appearing regions
    ranging in size from a few hundred to many
    thousands of kilometers
  • Sunspots last from a few days to a few months
  • They are darker because they are cooler (about
    4500K as compared to 6000 K)
  • They are cooler because they contain strong
    magnetic fields

Solar Magnetic Fields
  • On Earth our magnetic field drives matter to the
  • On the Sun the field slows the ascent of hot gas
    in the convection zone and because it starves the
    area above of heat it becomes cooler and darker
    creating a sunspot

Solar Magnetic Fields
Prominences and Flares
  • Take place in the Suns atmosphere
  • Prominences huge plumes of glowing gas that jut
    from the lower chromosphere into the corona
  • Solar flares Usually come from sunspots as a
    brief bright eruption of hot gas in the
  • Last only a few minutes or hours

Flares and Prominences
Heating of the Chromosphere and Corona
  • Heating caused by the magnetic field
  • More energy for smaller numbers of atoms
  • Like cracking the whip
  • Magnetic waves are created in the convective zone

The Solar Wind
  • Solar wind a tenuous flow of mainly hydrogen and
    helium that sweeps across the solar system
  • Creates comet tails and auroras
  • On average the wind speed is about 500 km/s (How
    long does it take to get to Earth?)

The Solar Cycle
  • Sunspot and flare activity change from year to
    year in what is called the solar cycle
  • The numbers clearly fall and rise approximately
    every 11 years
  • Discovered by Heinrich Schwabe
  • Flares and prominences also follow the solar
    cycle and Earths climate may be affected as well
  • May be as short as 7 years or as long as 16

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Cause of the Solar Cycle
  • Probably caused by the suns differential
    rotation (26 days at the equator and 30 at the
  • Differential rotation causes a winding up of the
    magnetic field
  • Eventually this winding gets too tight and

Links to our climate
  • Maunder Minimum period of time when the cycle
    turned off and Europe experienced 70 years of
    colder than normal weather called the Little Ice
  • This is a period of time of low solar activity