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22 Cards in this Set
- Front
- Back
The Sun's Structure: |
-Darkening around edges (cool atmosphere compared to hot inner core) -Sun spots -Luminosity = 3.8 x 10^26 -70% H, 28% He, 2% metal -Rotation rate 25 days (equator), 30 days (poles) -Surface Temp: 5800K (cooler at sunspots 4000K) -Core temp 15 million K -Average density of Sun (1g/cm^3) less than Earth (5.5g/cm^3) --> core so hot that density is lower than what you'd expect |
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Since we cannot directly make a spectrum of the Sun's core, how do we know that it is 15 million K? |
Directly observe the luminosity of the surface, & b/c of gravitational equilibrium, we know that the energy let off must be the same amount that is generated |
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Components of the Sun: |
Photosphere - thin outer layer (thinner than an orange peel)
Core - nuclear reactions take place (only place for energy generation)
Convection Zone - over turning layers of hot and cool gas (how energy gets out of last third of Sun)
Corona - gas surrounding the sun, part of the solar atmosphere (only seen in total solar eclipse) |
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Why is our Sun stable? |
Gravitational Equilibrium - if this wasn't true the Sun would cook down and collapse |
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What is the process of Nuclear Fusion? |
Building He nuclei out of H nuclei
4H (proton) --> 1 He (1 protons, 2 neutrons) + energy
Rearranging protons and neutrons among atomic nuclei -lots of potential energy b/c atoms of nucleus bound very tightly |
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How long would the Sun last if it were 1) burning 2) gravitationally contracting 3) nuclear fusion |
1) Burning - few thousand years (chemical reaction rearranging electrons among atoms
2) Gravitational Contraction - millions of years
3) Nuclear fusion - billions of years |
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Contrast Fission with Fusion |
Fission: "Breaking things apart" -Start with heavy nuclei (238U) -Unstable, so break apart (radioactivity), or break them apart with neutron (nuclear reactor)
Fusion: "Putting things together" -Start with simple nuclei (H) -Collide them together at high energy -Tremendous electric repulsion from protons, but Strong nuclear force binds them together releasing energy (increasing density(pressure)/temp so more particles collide) |
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Combining simple nuclei releases energy (nuclear fusion) up until which element? |
Iron -Iron is big enough that if you try to put two together, it requires energy rather than releasing it |
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Is there direct evidence that nuclear reactions are occurring in the center of the Sun? |
Solar Neutrinos!
-low mass, weakly interacting fundamental particles -to stop a neutrino, would need a lead shield 1 light year thick -neutrinos escape from the center of the sun |
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How does energy escape once created in the core of the Sun? |
Inner radiation zone - light scatters
Outer convective envelope - hot gas rises, cool stuff sinks
* Takes 200,000 years for energy to be release from the sun |
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What is solar weather caused by? |
Convective motion + Sun's rotation |
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What are the three ways that we can know anything about the interior of the Sun? |
1) Mathematical models + Consistency
2) Helioseismology -Convective motion of sun leads to solar oscillations (seismic waves) which can tell us about the interior of the sun
3) Solar neutrinos |
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What is the Solar Neutrino Problem? |
3 types of neutrinos and the take detected only 1 type (explains why it only detected 1/3 expected) |
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What causes aurora in the Earth's atmosphere? |
Solar wind
-see aurora in northern atmospheres, b/c aurora funnel some of solar wind down into magnetic poles of Earth (particles are high speed and collide with particles in our atmosphere which causes gases to glow) |
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What are sunspots? How are they created? |
-Magnetic field lines travel from one spot to another (with differing poles) -Sunspots are regions of very strong magnetic fields so they suppress convective motion locally (make regions slightly cooler -dark) |
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What is the sunspot cycle? |
11 year cycle (from almost no sunspots to maximum number) |
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What is the 22 year magnetic activity cycle of the Sun? |
Every 11 years the Sun's North and South pole switch
-reflects that both the magnetic field in the Sun and Earth are regenerating themselves
-this occurs in part of the differential rotation (faster at equator than poles) |
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What is the hypothesized explanation for whey there was no record for sunspots on the Sun between 1650 - 1700? |
"Little Ice Age" |
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What is the relationship between temperature on Earth and the Sun spot cycle? |
During periods where there are no sunspots, does seem to be cooler periods on earth
(can reconstruct temperature by looking at growth rings of trees)
**But we don't know if this is causation or just correlation |
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How do you prove causation? |
Double-blind experiment (use a experimental and control group) |
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What is the relationship between sample size and variation? |
Smaller the sample size, the larger the natural variation |
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What is the "butterfly diagram" for sunspot formation? |
Sunspots start up in mid-latitudes and as time goes on there are more sunspots and the move toward the equator -Magnetic field is stretched out at equator (spins faster here) |