Lecture 11 - Our Star Flashcards

1
Q

what are the 6 parts of the sun? and what happens in each

A
  1. solar core –> nuclear reactions, creates heat
  2. H and He gas but no nuclear reactions
  3. convection zone –> sends out energy via convection (hot gas rises, cool gas falls)
  4. photosphere –> visible surface of sun
  5. chromosphere –> middle layer of solar atmosphere, radiates most of sun’s UV light
  6. corona –> outer layer of solar atmosphere
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2
Q

how do nuclear reactions compare to chemical reactions?

A

nuclear reactions more efficient for producing energy

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3
Q

NUCLEAR FISSION
- what happens
- how does final mass compare to initial mass
- equation
- what happens to energy
- what is produced and why is this bad

A
  • break atoms apart
  • M > m+m
  • M = m+m +energy
  • energy released via E = mc2
  • releases unstable radioactive nuclei –> dangerous if not handled properly
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4
Q

NUCLEAR FUSION
- what happens
- equation
- what happens to energy

A
  • fuse 2 atoms together
  • m+m = M + energy
  • energy released via E = mc2
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5
Q

does the sun use nuclear fusion or fission? why?

A

FUSION
- sun has soup of hot gas with bare, positively charged atomic nuclei
- efficient and clean, no radioactive byproduct

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6
Q

is mass conserved in nuclear reactions?

A

YES

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7
Q

what is the 3rd type of nuclear reactions?

A

nuclear decay

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8
Q

describe the binding energy graph

A

energetically favourable to undergo FUSION of lighter elements to form iron –> increasing binding energy

energetically favourable to undergo FISSION of heavier elements to form iron –> decreasing binding energy

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9
Q

what is special about iron?

A

most stable element with lowest binding energy

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10
Q

why is it hard to start fusion on Earth?

A

requires A LOT of energy because light nuclei don’t know they prefer to be fused –> like charges repel so much have enough energy to push them together at high speed so nuclear force can take over

requires a lot of energy, but a lot is produced in return

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11
Q

why can the sun undergo fusion?

A

pressure, density, and heat at core of sun is large enough for nuclear fusion to occur easily —> overcomes energy requirement

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12
Q

what elements does the sun fuse? what is the process called and how does it work (3 steps)?

A

H fuses to He

via PP CHAIN
1. fuse 2 H protons to make DEUTERIUM (p+n)
2. deuterium interacts with another proton to make HELIUM 3 (p+p+n)
3. Two Helium 3 collide to form HELIUM 4 (p+p+p+n) and 2 extra protons

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13
Q

what is deuterium made of?

A

POSITRON –> antielectron
NEUTRON –> tiny mass

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14
Q

how much H is converted to He per second?
how long will it take for sun to run out of H?

A

4 million tons of H converted to He per second

takes 4 billion years to run out

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15
Q

what is released from fusion in the sun?

A

energy and radiation propagate outwards

light released (not particles) thru convective zone as heat

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16
Q

equation for release of energy from the sun

A

E = 0.007 (4m)c^2

4m = mass of 4 protons involved (6 protons enter, 2 protons leave)

energy difference btwn initial and starting products is 0.7%

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17
Q

how do you calculate # of atoms if sun was all hydrogen?

A

M_sun/M_Hatom

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18
Q

how do you calculate how much energy could be extracted from whole sun with pp chain?

A

E = mc^2
E = 0.007(# of atoms[10^57])mass of H*c^2

19
Q

how do you determine how long the sun will last based on the watts it emits?

A

W = J/s

J/(J/s) =time

20
Q

what would happen if the core temp increased? why does this happen?

A

high temp = more energy = more collisions = more fusion

higher core pressure exceeds gravity pressure so the core can expand and cools down

low temp = less energy = less collisions = less fusion

reaches gravitational equilibrium and energy balance is restored

BECAUSE SUN IS A SOLAR THERMOSTAT

21
Q

3 pieces of evidence for standard solar model

A
  1. fusion is the only way that the sun could produce enough energy
  2. sun composition is mostly H (76% H and 22% He)
  3. we can detect neutrinos from sun
22
Q

what do quarks form?

A

protons and neutrons

23
Q

what are 2 particles that are similar to electrons?

A

muons and tau

24
Q

what are neutrinos

A

produced due to fusion –> most abundant particles with mass in the universe

25
what is the solar neutrino problem?
HOMESTAKE mine detected too few neutrino reactions by a factor of 3 could solar model have been wrong? could the experiment have been wrong?
26
what was the solar neutrino solution? how did they solve the problem?
the solar model was correct but the homestake experiment only detected ELECTRON NEUTRINOS, which is only 1 type of neutrinos out of 3 SUDBURY NEUTRINO OBSERVATORY --> sensitive to all types of neutrinos
27
what is helioseismology?
studies oscillations of sun, vibrations of sun to see how heat works in the sun, internal movements and structure of sun supports solar model very well
28
temperature of core, photosphere, chromosphere, corona
1. CORE --> 15 million K 2. PHOTOSPHERE --> 5700 K 3. CHROMOSPHERE --> 10,000 K 4. CORONA --> 1,000,000 K
29
describe the visibility of the photosphere
deepest visible region density of gas is low enough (opacity is low enough) to let light leave from convection zone (below photosphere, gas is dense and opaque)
30
how is light transported in the radiation zone?
energy transported upwards by photons
31
what is solar wind?
flow of charged particles from surface of sun into solar system
32
what is gravitational eqb?
sun wants to collapse under gravity but fusion energy exerts
33
what is energy balance of the sun?
rate at which energy radiates from the surface of the sun is EQUAL TO the rate at which energy is released by fusion
34
what is the purpose of gravitational contraction? when did gravitational contraction stop?
provided energy that heated the core as the sun was forming contraction stopped when fusion began
35
how can we detect the sun's corona?
X-ray photos detect corona where magnetic fields trap hot gas
36
what is the role of the sun's magnetic field?
allows for high core temperature
37
describe TRACE detection of magnetic field loops
UV light shows loops as highly ionized iron atoms traveling thru magnetic fields
38
what are sunspots? what are they caused by? what do they indicate?
dark regions in photosphere that are cooler than their surroundings caused by magnetic fields that inhibit convection only indicate temperature, they are not shadows!
39
what are solar flares? what are they caused by?
lots of high energy plasma escapes, allowing X-rays and charged particles to go into space due to reconnection event of magnetic field lines in coronal holes
40
what leads to solar wind?
solar flares
41
what leads to auroras? why don't they hit earth?
large mass ejections from solar flares don't hit earth bc of earth's magnetic field
42
how do sunspots vary?
number of sunspots varies in 11-year cycle
43
what happens at the peak of solar cycle?
SOLAR MAXIMA
44
how long is the solar cycle?
22 years but the sun's magnetic field flips every 11 years