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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

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

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)

Why is our Sun stable?

Gravitational Equilibrium - if this wasn't true the Sun would cook down and collapse

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

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

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)

Combining simple nuclei releases energy (nuclear fusion) up until which element?


-Iron is big enough that if you try to put two together, it requires energy rather than releasing it

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

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

What is solar weather caused by?

Convective motion + Sun's rotation

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

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)

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)

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)

What is the sunspot cycle?

11 year cycle (from almost no sunspots to maximum number)

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)

What is the hypothesized explanation for whey there was no record for sunspots on the Sun between 1650 - 1700?

"Little Ice Age"

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

How do you prove causation?

Double-blind experiment (use a experimental and control group)

What is the relationship between sample size and variation?

Smaller the sample size, the larger the natural variation

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)