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PHYS 183 > Lecture 11 - Our Star > Flashcards

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
Q

what is the solar neutrino problem?

A

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
Q

what was the solar neutrino solution? how did they solve the problem?

A

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
Q

what is helioseismology?

A

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
Q

temperature of core, photosphere, chromosphere, corona

A
  1. CORE –> 15 million K
  2. PHOTOSPHERE –> 5700 K
  3. CHROMOSPHERE –> 10,000 K
  4. CORONA –> 1,000,000 K
29
Q

describe the visibility of the photosphere

A

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
Q

how is light transported in the radiation zone?

A

energy transported upwards by photons

31
Q

what is solar wind?

A

flow of charged particles from surface of sun into solar system

32
Q

what is gravitational eqb?

A

sun wants to collapse under gravity but fusion energy exerts

33
Q

what is energy balance of the sun?

A

rate at which energy radiates from the surface of the sun is EQUAL TO the rate at which energy is released by fusion

34
Q

what is the purpose of gravitational contraction?

when did gravitational contraction stop?

A

provided energy that heated the core as the sun was forming

contraction stopped when fusion began

35
Q

how can we detect the sun’s corona?

A

X-ray photos detect corona where magnetic fields trap hot gas

36
Q

what is the role of the sun’s magnetic field?

A

allows for high core temperature

37
Q

describe TRACE detection of magnetic field loops

A

UV light shows loops as highly ionized iron atoms traveling thru magnetic fields

38
Q

what are sunspots?

what are they caused by?

what do they indicate?

A

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
Q

what are solar flares? what are they caused by?

A

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
Q

what leads to solar wind?

A

solar flares

41
Q

what leads to auroras? why don’t they hit earth?

A

large mass ejections from solar flares

don’t hit earth bc of earth’s magnetic field

42
Q

how do sunspots vary?

A

number of sunspots varies in 11-year cycle

43
Q

what happens at the peak of solar cycle?

A

SOLAR MAXIMA

44
Q

how long is the solar cycle?

A

22 years but the sun’s magnetic field flips every 11 years

PHYS 183 (20 decks)

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