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AST > Test 3 > Flashcards

Test 3 Flashcards

1
Q

What is an arc second?

A

the measurement of a parallax angle that is really small

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2
Q

What is an arc second?

A

the measurement of a parallax angle that is really small

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3
Q

What is a light year?

A

the distance light travels in one year

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4
Q

How does a light year compare to an parsec?

A

3 1/4 light years = 1 parsec

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5
Q

What is the system of stellar magnitudes?

A

O-B-A-F-G-K-M

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6
Q

how was the system originally set up?

A

it was originally based on the hydrogen absorbtion lines

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7
Q

Today a difference of 5 magnitudes corrisponds to what?

A

a factor in brightness of 100

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8
Q

What is the apparent magnitude?

A

measure how bright a star appears to be in the sky

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9
Q

what is absolute magnitude?

A

measure the intrinsic brightness of a star. Absolute magnitude equals what the apparent magnitude would be if the star was 10 parsecs away

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10
Q

What distance would a stars apparent brightness = the stars absolute magnitude?

A

at a distance of 10 parsecs away

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11
Q

what are the apparent and absolute magnitude of the sun?

A 
Apparent = -26.7
Absolute = 4.8
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12
Q

What was the original system of classification based on?

A

it was based on hydrogen absorption lines

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13
Q

what is the order of bightness going from hot to cool?

A

O-B-A-F-G-K-M

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14
Q

in which spectral class of the stars are the absorption lines of hydrogen the strongest?

A

A

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15
Q

What is the spectral type of the sun?

A

G2

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16
Q

what is HR diagram?

A

shows the life cycle of a star

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17
Q

what is along the horizontal and vertical axis?

A 
Horizontal = Temp at surface
Vertical = Brigthness
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18
Q

what property of a star determines its position on the main sequence?

A

The mass

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19
Q

What are red giants?

A

stars in the process of dying

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20
Q

What are white dwarfs?

A

dead embers of stars

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21
Q

What is hydro static equilibrium?

A

every layer of a star has to be ina pressure balance between gravity that wants to pull the gas inward and internal pressure that wants to push the as outward.

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22
Q

how does the pressure in a star change when going from the surface of the star to the center?

A

the pressure will increase

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23
Q

in what two ways can a star transport energy outwards?

A

.

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24
Q

what one factor determines where a star will be found on the main sequence?

A

the mass of a star

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25
Q

how does the main sequence lifetime depend on the mass and luminosity of a star?

A

life time = mass / luminosity

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26
Q

What will be the total main sequence life time for the sun?

A

10 billion years

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27
Q

what will be the life time of a massive O star ?

A

1 million years

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28
Q

What about a low mass M star?

A

300 billion years

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29
Q

What is the ZAMS

A

Zero age main sequence

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30
Q

how is the core of a star changing during the entire main sequence lifetime

A

drastic changes on the inside cause smaller changes on the outside

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31
Q

in what 3 ways does the surface of a star change during its main sequence lifetime

A

its gets a little bigger, brighter and cooler

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32
Q

How can we tell the age of a star cluster?

A

.

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33
Q

when the neuclear reactions in the core end the core begins to the contract. Why?

A

.

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34
Q

how do you understand what happens to the core in terms of hydro static equilibrium?

A

.

35
Q

as the core contracts there are now two energy sources in the center. what are they?

A

.

36
Q

how does the energy from the stars center now compare to the energy produced when the star was on the main sequence?

A

.

37
Q

what happens to the outer layers of the star?

A

.

38
Q

What is a light year?

A

the distance light travels in one year

39
Q

How does a light year compare to an parsec?

A

3 1/4 light years = 1 parsec

40
Q

What is the system of stellar magnitudes?

A

O-B-A-F-G-K-M

41
Q

how was the system originally set up?

A

it was originally based on the hydrogen absorbtion lines

42
Q

Today a difference of 5 magnitudes corrisponds to what?

A

a factor in brightness of 100

43
Q

What is the apparent magnitude?

A

measure how bright a star appears to be in the sky

44
Q

what is absolute magnitude?

A

measure the intrinsic brightness of a star. Absolute magnitude equals what the apparent magnitude would be if the star was 10 parsecs away

45
Q

What distance would a stars apparent brightness = the stars absolute magnitude?

A

at a distance of 10 parsecs away

46
Q

what are the apparent and absolute magnitude of the sun?

A

Apparent =

Absolute =

47
Q

What was the original system of classification based on?

A

it was based on hydrogen absorption lines

48
Q

what is the order of bightness going from hot to cool?

A

O-B-A-F-G-K-M

49
Q

in which spectral class of the stars are the absorption lines of hydrogen the strongest?

A

A

50
Q

What is the spectral type of the sun?

A

G2

51
Q

what is HR diagram?

A

shows the life cycle of a star

52
Q

what is along the horizontal and vertical axis?

A 
Horizontal = Temp at surface
Vertical = Brigthness
53
Q

what property of a star determines its position on the main sequence?

A

.

54
Q

What are red giants?

A

stars in the process of dying

55
Q

What are white dwarfs?

A

dead embers of stars

56
Q

What is hydro static equilibrium?

A

every layer of a star has to be ina pressure balance between gravity that wants to pull the gas inward and internal pressure that wants to push the as outward.

57
Q

how does the pressure in a star change when going from the surface of the star to the center?

A

the pressure will increase

58
Q

in what two ways can a star transport energy outwards?

A

.

59
Q

what one factor determines where a star will be found on the main sequence?

A

the mass of a star

60
Q

how does the main sequence lifetime depend on the mass and luminosity of a star?

A

life time = mass / luminosity

61
Q

What will be the total main sequence life time for the sun?

A

10 billion years

62
Q

what will be the life time of a massive O star ?

A

1 million years

63
Q

What about a low mass M star?

A

300 billion years

64
Q

What is the ZAMS

A

Zero age main sequence

65
Q

how is the core of a star changing during the entire main sequence lifetime

A

drastic changes on the inside cause smaller changes on the outside

66
Q

in what 3 ways does the surface of a star change during its main sequence lifetime

A

its gets a little bigger, brighter and cooler

67
Q

How can we tell the age of a star cluster?

A

.

68
Q

when the neuclear reactions in the core end the core begins to the contract. Why?

A

.

69
Q

how do you understand what happens to the core in terms of hydro static equilibrium?

A

.

70
Q

as the core contracts there are now two energy sources in the center. what are they?

A

.

71
Q

how does the energy from the stars center now compare to the energy produced when the star was on the main sequence?

A

.

72
Q

what happens to the outer layers of the star?

A

.

72
Q

How have the surface temp and luminosity changed as they move into the red giant region?

A

The temp gets cooler and the luminosity gets brighter.

73
Q

What is this called and what element results from this reaction?

A

Helium fusion and it is 3helium to 1carbon plus energy

74
Q

At what temp does helium fusion start?

A

1million kelvin

75
Q

The rate of helium fusion reaction increases very rapidly with increasing temp.how does this lead to an explosion?

A

Because the electrons are squeezed to tightly

76
Q

How does the star move on the hr diagram after e star settles down to steady helium burning?

A

Moves left closer to the main sequence

77
Q

What happens to the core when it runs out of helium?

A

It starts burning carbon

78
Q

Will the sun ever burn elements past helium ?

A

Yes it will burn carbon

79
Q

What is a planetary nebula?

A

A supergiant star that pushes of its outer layers of gas

80
Q

What heats the gas in a planetary nebula and causes it to glow?

A

The uv light heats up e gas and causes it to glow

81
Q

Why can’t the nuclear burning of iron occur?

A

Because fusion of iron will not give you energy out of the reaction

82
Q

Once the core is full of iron what happens to the core?

A

When the core is big enough it will implode

AST (1 decks)

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