Transcript The Sun: Our Extraordinary Ordinary Star

The Sun: Our Extraordinary
Ordinary Star
Chapter 7: Page 235
Importance
• Early Man revered the sun
– They recognized the importance of the sun to life
on earth.
• The goings and comings of the sun were
carefully studied
– Stonehenge
• Early Greeks
– Estimated the size and distance of the sun
Average
• Mass
– Not most massive or least massive
• Size
– Not largest or smallest
• Brightness
– Not brightest or least bright
• Just sort of “Ordinary”
– But that is good for us
What we see…
• Be careful looking at the sun- never through a
telescope. Use #14 welder’s glass or special
coated Mylar sheets.
• We see the photosphere
– Lower of 3 outer regions
– Appears different depending on where we look
• During total solar eclipse we see
Corona and chromosphere
Solar Granulation
Granulation in the Photosphere
• Blotchy pattern = granulation
• 1000 km across
• Light colored areas surrounded by relatively
darker boundaries
• Several million cover the surface at any time
• Hot gases move upward at the center – bright
• Cooler gas move downward at the edges darker
• Convection currents bring hot gases to the
surface where they cool and sink
Center is
100 K
hotter than
edge
Chromosphere
• Chromo = color but it is visible only during a
total solar eclipse
• Dim layer of less dense stellar gas
• Pinkish strip 200 km thick
• Spicules – jets of gas shooting up 1000 km
• 1/3 of a million at any given time covering a
few percent of the Chromosphere
• Occur at boundaries of supergranules
– slightly larger than Earth
– contains 900 granules
1-2 million K
10,000 K
4000 K
5800 K
Temperature of Outer Layers
• Move farther from a fire and temperature
drops.
• Move farther from photosphere of sun and
temperature increases
• Corona contains ionized gases- plasma
– Electrons stripped
– Iron with 13 electrons removed
• Heat from Energy carried up from the core by
complex magnetic field
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•
Solar Wind
Gas in corona is moving fast because of temperature.
Gas escapes the Gun’s gravity
Particles move out from the sun in the Solar Wind
Solar wind “protects” solar system from material
from other stars or systems
• Contains
– 99.9% electrons, hydrogen, helium
– Silicon, sulfur, calcium, chromium, nickel, neon, argon
• Heliosphere- bubble surrounding the solar system
created by the solar wind particles
Active Sun
• Sun spots and related activity
• Plages (plahzh) Hotter, brighter areas
– Precede sun spots
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Filaments- dark streaks
Prominences- gigantic loops or arcs
Solar Flares- violent eruptions
Coronal Holes- darker, cooler regions
Coronal Mass Ejections
• Observed
Sun Spots
– Chinese astronomers 2000 yrs ago
– Observed by Galileo
• Explained
– Cooler regions on the Sun’s surface
– Umbra: Center is cooler - 4300 K
– Penumbra: Cool feather region around – 5000 K
– Sun’s surface - 5800 K
Center is
100 K
hotter than
edge
Sun Spot Cycles
• 11 year cycle
– Number of sunspots increase from max to min
– Location varies beginning at 30oN or S then middle
• Directly linked to magnetic field of the sun
– Concentrated north or south magnetic poles
project through photosphere
– Magnetic field repells ionized gases preventing
them from rising to the “surface”
– Cooler and darker than surrounding area
22 year cycle
• Sun spots and sunspot groups come in pairs
– Hemispheres differ
– N magnetic pole points out of one and S magnetic
pole points out of the other.
• Every 11 years sun’s magnetic field reverses
– For 11 years N mag points out of top hemisphere
– For 11 years S mag points out of top hemisphere
11 year cycles and location of sun spots
11 year cycles and location of sun spots
Maunder Minimum
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•
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1645-1715 Almost no sun spots
Extreme Cold in Europe
“Little Ice Age”
Severe Droughts in Western North America
2010- ?
Sun Spot Related Activity
• Plages (plahzh) Hotter, brighter areas
– Precede sun spots
•
•
•
•
•
Filaments- dark streaks
Prominences- gigantic loops or arcs
Solar Flares- violent eruptions
Coronal Holes- darker, cooler regions
Coronal Mass Ejections
Plages (plahzh)
• Very bright areas on the sun’s surface
• Occur often appear just before sun spots
appear near by.
• Theory – plages are caused by magnetic fields
crowding up from below and compressing the
gas. Compressed gas becomes hotter and
therefore brighter.
Filaments and Prominences
• Huge volumes of gas lifted upward from the
photosphere by the sun’s magnetic field.
• Viewed from above the gas appears dark
because it cools- filaments.
• Viewed from the side the gas looks like giant
loops and arches- prominences.
Solar
Prominence
Solar Ejections
• Solar Wind – constant ejection of material
(plasma) from the sun.
– 1 million ton of material per second
• Solar flares – violent eruptions of high-energy
particles lasting less than an hour.
• Coronal Mass Ejections – huge balloon-shaped
volumes of high energy gas
– Trillions of tons
Solar Activities and Communication
• Solar activity associated with sun spots result
in massive amounts of radiation and charged
particles being ejected into space.
• When this material overwhelms the protective
Van Allen Belt layer of our atmosphere all
electromagnetic activities can be interrupted.
– Electronic communication
– Electrical Distribution
– Satellites
Sun Spot Update
How does the sun keep burning?
• Earth has existed in its present condition for at least
hundreds of million years.
• If sun were burning coal or hydrogen gas would burn
for only 5000 years.
• So energy from the sun does not come from normal
combustion.
• 1905 Einstein
• E= mc2 c= 3.00 x 108 m/s
•
c2 = 9.00 x 1016 m2 /s2
• Small amount of mass large amount of energy
Thermonuclear Fusion
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•
•
•
Requires very high temperatures
> 10 x 106 K
Interior of the sun 15.5 x 106 K
Hydrogen fuses to form Helium with a
decrease in mass which is converted to
energy.
Appendix
A
Page A-29
Neutrinos (little neutrons)
• Proton Changes into a Neutron
– Releases gamma ray photons
– Releases a Neutrino- 1038 per second from sun
• Neutrino
– Almost massless
– Uncharged particle
– Difficult to detect
• Detect a neutrino
– If we could detect we could know what goes on in the middle of
the sun (a neutrino telescope)
– Neutrino strikes a neutron changes to a proton
– C2Cl4 dry cleaning fluid (carbon tetrachloride,
perchloroethylene)
– Changes chlorine atom into a radioactive argon atom
– Can detect radioactive atoms