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astronomy > AST EXAM 3 > Flashcards

AST EXAM 3 Flashcards

1
Q

what two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

A

gravitational force and outward gas pressure

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2
Q

T/F: nuclear power plants on earth create energy in the same way as the sun

A

false

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3
Q

from center outward, which of the following lists the layers of the sun in the correct order

A

core, radiation zone, convection zone, photosphere, chromosphere, corona

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4
Q

why do sunspots appear dark?

A

they are regions that are significantly cooler than the rest of the photosphere

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5
Q

the sun has enough nuclear fuel to last for another

A

5 billion years

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6
Q

suppose you try to bring two protons close together, because of the electromagnetic force, the two protons will

A

repel on another

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7
Q

what is the approx temp of the sun’s core

A

15 million K

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8
Q

the star Alpha Centauri A is the same type of star as the sun, but its luminosity is about 1.6 times that of the sun, what can we conclude

A

ACA fuses hydrogen into helium in its core at a higher rate than our sun

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9
Q

approximately, what is the sun made of

A

70% H, 28% HE, 2% other elements

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10
Q

based on its surface temp of 6,000K, most photons that leave the sun’s surface lie in which region of the electromagnetic spectrum

A

visible

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11
Q

true or false: the corona and chromosphere are hotter than the photosphere

A

true

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12
Q

what is the solar wind

A

a stream of charged particles flowing outward from the surface of the sun

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13
Q

which of the following is the phase of matter in the interior of the sun

A

plasma

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14
Q

if the suns surface cooled, how would its appearance change

A

it would appear more red

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15
Q

the suns surface is called the

A

photosphere

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16
Q

true or false: the sun rotates more quickly at the equator than at the poles

A

true

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17
Q

by what process does the sun generate energy

A

nuclear fusion

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18
Q

what happens to energy in the sun’s convection zone

A

energy is transported outward by the rising of hot plasma

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19
Q

if star A is closer to us that Star B, then star A’s parallax angle is

A

larger than that of Star B

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20
Q

the spectral sequence sorts stars according to

A

surface temps

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21
Q

the faintest star visible to the naked eye has an apparent magnitude of about

A

6

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22
Q

star A has a absolute magnitude of 3, and star B has an absolute magnitude of 5, which star is brighter in our sky

A

there is not enough info to answer the question

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23
Q

which of the following is the most numerous type of main-sequence star

A

an M star

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24
Q

which of the following stars has a spectrum that peaks at the shortest wavelength

A

a blue star

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25
Q

which of the following best describes the axes of a Hertzsprung-russel disgram

A

surface temperature on the horizontal axis and luminosity on the vertical axis

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26
Q

ten parsecs is about

A

32.6 light-years

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27
Q

on a H-R diagram, stellar radii

A

increase diagonally from the lower left to the upper right

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28
Q

the total amount of power that a star radiated into space is called its

A

luminosity

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29
Q

the stellar spectral sequence, in order of decreasing temperatures is

A

OBAFGKM

30
Q

which star is the hottest star

A

O

31
Q

which of the following luminosity classes refers to stars on the main sequence

A

V

32
Q

on a H-R diagram, where would you find stars that are cool and luminous

A

upper right

33
Q

on a main sequence ,stars obtain their energy

A

by converting hydrogen to helium

34
Q

you observe a star and you want to plot it on a H-R diagram, you will need to measure all of the following, except the star’s

A

mass

35
Q

how is the lifetime of a star related to its mass

A

more massive stars live much shorter lives than less massive stars

36
Q

which of the following statements about spectral types of stars is not generally true

A

the spectral type of a star can be used to determine its distance

37
Q

The basic fusion reaction through which the Sun produces energy is __________.

A

Four hydrogen nuclei fuse to make one helium nucleus

38
Q

The energy that is released in the hydrogen fusion reaction comes from __________.

A

The difference in mass between the four hydrogen nuclei and the single resulting helium nucleus

39
Q

Place the layers of the Sun into the correct order from innermost at left to outermost at right.

A

Core, Radiation zone, convection zone, photosphere, chromosphere, corona

40
Q

All the phenomena of solar activity — including sunspots, flares, coronal mass ejections, and the sunspot cycle — are tied to changes in the Sun’s __________.

A

magnetic field

41
Q

Rank the layers of the Sun based on their density, from highest to lowest.

A

Core, radiation zone, convection zone, photosphere, chromosphere, corona

42
Q

In which of the following layer(s) of the Sun does nuclear fusion occur?

A

core

43
Q

What two items on the list below are in balance in what we call gravitational equilibrium?

A

gas pressure and gravity

44
Q

To place a star on an H-R diagram, we must know its __________.

A

surface temp and luminosity

45
Q

On the H-R diagram, most stars fall into the region labeled ____________.

A

main sequence

46
Q

Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.

A

cooler and larger in radius

47
Q

Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.

A

hotter and smaller in radius

48
Q

what is the fate of an isolated brown dwarf

A

it will remain a brown dwarf forever

49
Q

which of the following masses separates low mass stars from high mass stars

A

about 2 solar masses

50
Q

how does the surface temp and luminosity of a protostar compare to the surface temp and luminosity of the main sequence star it becomes

A

a main sequence star is hotter and dimmer than it was as a protostar

51
Q

what core temp is required before hydrogen fusion can begin in a star

A

Ten mil K

52
Q

what is a protostar

A

a star that is still in the process of forming

53
Q

what would happen if the sun was a black hole

A

NOTHING

54
Q

what is the max mass of a white dwarf

A

1.4

55
Q

max mass of a neutron star?

A

3

56
Q

Stars that are fusing hydrogen in their cores are

A

main-sequence stars

57
Q

what is a nova

A

The temperature of accreted matter eventually becomes
hot enough for hydrogen fusion. Fusion begins
suddenly and explosively

58
Q

what is a massive star super nova

A

Iron core of a massive star reaches
white dwarf limit and collapses into a
neutron star, causing total explosion.

59
Q

what is a white dwarf supernova

A

Carbon fusion suddenly begins as a white
dwarf in close binary system reaches
white dwarf limit, causing total explosion.

60
Q

what is the mass of the sun

A

2 X 10 to the 30 kg

61
Q

what is the rotation period of the sun

A

25 days

62
Q

true or false: bigger stars are built faster than smaller stars

A

TRUE

63
Q

what are sunspots

A

Are cooler than other parts of the Sun’s surface (4000 K) Are regions with strong magnetic fields

64
Q

a neutron star is

A

the core remnant of a star that died in a massive star supernova

65
Q

which of the following is closest in mass to a typical white dwarf

A

the sun

66
Q

the minimum mass of a black hole that forms during a massive star supernova is roughly

A

3 solar masses

67
Q

a white dwarf is mostly made of

A

carbon

68
Q

what triggers a nova explosion

A

hydrogen gas from a companion star builds up on the surface of the white dwarf and when the temp gets high enough, it fuses to helium

69
Q

true or false: our sun will likely undergo a nova event in about 5 billion years

A

false

70
Q

true or false:the remnant left behind by a white-dwarf supernova is a neutron star

A

false

71
Q

true or false: there is no upper limit to the mass of a neutron star

A

false

72
Q

which of the following best describes a black hole

A

a place from which the escape velocity exceeds the speed of light

astronomy (5 decks)

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