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Astronomy > Chapter 11: Our Star > Flashcards

Chapter 11: Our Star Flashcards

1
Q

gravitational equilibrium

A

energy supplied by fusion maintains the pressure that balances the inward crush of gravity

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2
Q

energy balance

A

the rate at which energy radiated from the surface of the sun must be the same as the rate at which it is released by fusion in the core

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3
Q

gravitational contraction

A

the process in which gravity causes an object to contract, thereby converting gravitational potential energy into thermal energy

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4
Q

when provided the energy that heated the core as the sun was forming

A

contraction stopped when fusion began

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5
Q

sun’s radius

A

6.9 x 10^8 m (109 times the earth)

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6
Q

sun’s mass

A

2 x 10^30 kg (300,000 times the earth)

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7
Q

sun luminosity

A

3.8 x 10^26 watts

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8
Q

solar wind

A

a flow of charged particles from the surface of the sun

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9
Q

corona

A

outermost layer of solar atmosphere (around 1 million K)

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10
Q

chromosphere

A

middle layer of solar atmosphere (around 100,000-1,000,000 K)

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11
Q

photosphere

A

visible surface of Sun (around 6000 K)

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12
Q

convection zone

A

energy transported upward by rising hot gas

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13
Q

radiation zone

A

energy transported upwards by photons

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14
Q

core

A

energy is generated by nuclear fusion of hydrogen into helium (around 15 million K)

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15
Q

fission

A

big nucleus splits into smaller pieces (ex: nuclear power plants)

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16
Q

fusion

A

small nuclei stick together, making a bigger one (ex: the sun, stars)

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17
Q

solar thermostat

A

the regulation of the sun’s core temperature that comes when the sun is in both energy balance and gravitational equilibrium

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18
Q

decline in core temp causes fusion rate to drop so…

A

core contracts and heats up

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19
Q

rise in core temp causes fusion rate to rise so…

A

core expands and cools down

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20
Q

solar neutrino problem

A

disagreement between the predicted and observed neutrinos coming from the sun

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21
Q

why does the sun emit neutrinos

A

fusion in the suns core create neutrinos when protons turn into neutrons

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22
Q

facts about timeline of solar neutrino problem

A

-early searches failed to find predicted number
-recent observations find the right number neutrinos but some have changed form

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23
Q

sunspots

A

blotches on the sun that appear darker than surrounding regions
- cooler than other parts of suns surface
-regions with strong magnetic fields

24
Q

satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum….

A

because Earth’s atmosphere tends to expand during solar maximum exerting more drag on satellites in low orbits

25
Q

solar flares

A

huge and sudden release of energy on the solar surface, probably caused when energy stored in magnetic fields is suddenly released

26
Q

what are solar flares caused by?

A

magnetic activity

27
Q

what do solar flares send into space?

A

bursts of x-rays and charged particles

28
Q

coronal mass ejections

A

bursts of energetic charged particles from the sun’s corona out through the solar system

29
Q

how can we best observe the sun’s chromosphere and corona?

A

-the chromosphere is best observed with ultraviolet telescopes
-corona best observed with x-ray telescopes

30
Q

what determines the total amount of incoming sunlight?

A

a planet’s distance from the sun

31
Q

what affects the temp differences of day and night?

A

rotation rate

32
Q

reflectivity (albedo)

A

fraction of incoming sunlight it reflects
- low albedo planets absorb more sunlight leading to hotter temps

33
Q

planet with highest average surface temp

A

venus, because its dense carbon dioxide atmosphere

34
Q

Venus temp without greenhouse effect

A

510 degrees Celsius colder

35
Q

Earth temp without greenhouse effect

A

31 degrees Celsius colder

36
Q

What would happen is the Earth was more reflective?

A

temp would go down

37
Q

What would happen is the Earth did not have an atmosphere?

A

temp would go down more than 10 degrees Celsius

38
Q

Ionization

A

removal of an electron

39
Q

Dissociation

A

destruction of a molecule

40
Q

scattering

A

change in photon’s direction

41
Q

absorption

A

photon’s energy is absorbed

42
Q

What can ionize and dissociate molecules?

A

x-rays and UV light

43
Q

what do molecules scatter more, blue or red light?

A

blue light

44
Q

what light can molecules absorb?

A

infrared light

45
Q

troposphere

A

lowest layer of Earth’s atmosphere
- temp drops with altitude
- warmed by infrared light from surface and convection

46
Q

convection

A

process in which warm materials expand and rise while cool material contract and fall

47
Q

stratosphere

A

layer above the troposphere
- temp rises with altitude in lower part, drops with altitude in upper part
- warmed by absorption of ultraviolet sunlight

48
Q

thermosphere

A

layer at about 100 km altitude
-temp rises with altitude
-x-rays and ultraviolet light from sun heat and ionize gases

49
Q

exosphere

A

highest layer in which atmosphere gradually fades into space
- temp rises with altitude, atoms can escape into space
- warmed by x-rays and UV light

50
Q

why is the sky blue?

A

air molecules scatter blue light more than red light

51
Q

why are sunsets red?

A

red light scatters less

52
Q

why is earth the only planet with a stratosphere?

A

UV absorbing ozone molecules
- protect us from sun’s UV light

53
Q

what do magnetic fields of Earth’s atmosphere do?

A

protect us from charged particles streaming from the sun

54
Q

aurora

A

glow of charged particles from solar wind energizing upper atmosphere near magnetic poles

55
Q

what is the sun made of (by mass)

A

70% hydrogen, 28% helium, 2% other elements

Astronomy (7 decks)

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