You could fit 109 Earths end to end in the Sun.

1

• You could fit 109 Earths end to end in the Sun.
• The Sun has a mass of 2 x 1030 kg
• ( 1 solar mass 1 M?)
• (333,000 times Earths mass).
• The Sun is composed mostly of Hydrogen and some
  Helium
• (and 2 other elements).
• The Sun is completely gaseous.
• The Sun generates energy in its core.
• The Sun has a strong magnetic field (compared to
  Earth).

2
Layers of the Sun
3
Energy Transport

• Radiation transport of energy due to
  propagation of photons.
• Convection Circulation in a fluid driven by
  heat.

4
Granulation

• Granules
• About the size of Texas.
• Last for 10 20 minutes.
• Based on spectroscopic data
• Brighter centers
• Stefan-Boltzmann Law - Center hotter than edges.
• Center blueshifted, edge redshifted
• Center rising, edge sinking.
• Convection!

5
The Photosphere

• Visible surface of the Sun.
• Avg. thickness 500 km.
• Radiates strongest in visible light.
• Surface temperature 5800 K.
• Very low density
• 3400x less dense than our air.
• Surface appears grainy.
• Granulation
• Dark regions observed.
• Sunspots

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Sunspots

• Position and number of sunspots change over time.
• The Sun rotates differentially
• 25.4 days at equator
• 27.8 days at 45º
• 11 year cycle of sunspot activity.
• 2001 Sunspot maximum (around 100 spots
  visible).
• 5.5 yrs. later Sunspot minimum (only a few
  spots visible).
• 22 year cycle of sunspot activity.
• The polarity of the sunspots flip every 11
  years, so a full cycle is actually 22 years.

7
The Zeeman Effect

• Spectral observations of sunspots show a
  splitting of emission lines.
• Splitting occurs due to the presence of a
  magnetic field.
• The Suns magnetic field is a few thousand times
  stronger than Earths.
• Prohibits rising gas from delivering heat to the
  surface.
• Dark regions on the Sun.
• Actually, cooler regions
• (lower temp. -gt less intense).
• Temperature 4240 K.

8
The Cause of Sunspots

• Differential rotation drags the equatorial part
  of the magnetic field ahead.
• As the Sun rotates, the magnetic field is
  eventually dragged all the way around.
• Differential rotation wraps the Sun in many turns
  of its magnetic field.
• Where loops of tangled magnetic field rise
  through the surface, sunspots occur.

9
The Chromosphere

• Layer above the photosphere.
• Avg. thickness 13,000 km.
• Radiates in Hydrogen Balmer
• Emission spectrum.
• Pink color (chromo color).
• Density 10-8 times our air.
• Temperature increases rapidly with height.

10
The Corona

• Layer above the chromosphere.
• Imaged extending out at least 20 solar radii.
• (10 of the distance to Earth).
• Observed during solar eclipses.
• Too dim to see unless photosphere blocked out.

• Radiates strongest in X-rays.
• Avg. temp. 106 K.
• Gas believed to be heated by magnetic field loops
  extending into the chromosphere and corona,
  agitating the gas.

11
The Solar Wind

• Gas follows magnetic field lines.
• Sometimes the magnetic field lines break apart,
  sending the gas streaming outward in a solar
  wind.
• Near Earth, the wind travels at around 300 800
  km/s.
• Source of solar wind coronal holes.

12
Prominences

• Active regions (regions of disturbed activity)
  observed in other layers as well.
• Prominences hot ionized gas trapped in magnetic
  field lines.

13

• TRACE image of filaments of hot gas ( 106 K).

14
Solar Flares

• When magnetic fields become too twisted, they
  sometimes cancel each other out and reconnect.
• Stored energy is released as photons and charged
  particles.

15
Coronal Mass Ejections

• Coronal Mass Ejections Giant magnetic bubbles
  of ionized gas that separates from the rest of
  the solar atmosphere and escapes into
  interplanetary space.

The Sun (for size comparison), blocked out by a
filter.
16

• Four images of the Sun, taken simultaneously.
• Notice the locations of sunspots, active regions,
  prominences, etc.

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Nuclear Fusion

• The Sun radiates energy due to nuclear reactions
  in its core.
• Due to high temperature and pressure, the gas is
  totally ionized.
• Nuclear Fusion lighter nuclei combine to create
  heavier nuclei, releasing energy in the process.
• Conservation of Mass and Energy Matter and
  energy cannot be created or destroyed, but can be
  transformed from one form into another.
• E mc2
• (amount of energy amount of mass x the speed
  of light, squared).

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Hydrogen Fusion

• At high enough temperature and pressure, 4
  hydrogen nuclei (protons) can fuse into a helium
  nucleus (two protons and two neutrons).
• In the process, mass is converted into energy.

• 4 1H -gt 4He energy
• Proton-proton chain A set of three reactions
  which converts 4 hydrogen nuclei into one helium
  nucleus.