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Astronomy > Final review > Flashcards

Final review Flashcards

1
Q

The Earth revolves around the Sun once each

a) day
b) month
c) year

A

Year

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2
Q

The average temperature is hotter in summer than winter. This is ultimately caused by

a) the greenhouse effect that warms the Earth by trapping infrared radiation.
b) the fact that the Earth is closer to the Sun in summer.
c) the tilt of the Earth’s axis relative to the Earth’s orbit.
d) the fact that the Sun emits more energy per second in the summer than it does in the winter

A

c) the tilt of the Earth’s axis relative to the Earth’s orbit.

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3
Q

The average temperature is hotter in summer
than winter. This is ultimately caused by

a) the greenhouse effect that warms the Earth by trapping infrared radiation.
b) the fact that the Earth is closer to the Sun in summer.
c) the tilt of the Earth’s axis relative to the Earth’s orbit.
d) the fact that the Sun emits more energy per second in the summer than it does in the winter

A

c) the tilt of the Earth’s axis relative to the Earth’s orbit.

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4
Q

How many days during each year is the Sun directly over the equator?

a) 1
b) 2
c) 182 or 183
d) 365

A

b) 2

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5
Q

The shortest night in Madison is on

a) the winter solstice
b) the spring equinox
c) the autumn equinox
d) the summer solstice

A

d) the summer solstice

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6
Q

The shortest night in Madison is on

a) the winter solstice
b) the spring equinox
c) the autumn equinox
d) the summer solstice

A

d) the summer solstice

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7
Q
  1. Where on Earth are you if Polaris is on your horizon?

a) north pole
b) south pole
c) Tropic of Cancer
d) Tropic of Capricorn
e) equator

A

e) equator

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8
Q

If the Moon’s orbit were exactly in the plane of the Earth’s orbit about the Sun, one would expect an eclipse of the Moon to occur about once every

a) week
b) 2 weeks
c) month
d) year
e) never

A

c) month

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9
Q

At full moon, as seen from the Earth, the Moon lies

a) opposite the Sun
b) 90 degrees east of the Sun
c) 90 degrees west of the sun
d) close to the Sun in the sky

A

a) opposite the Sun

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10
Q

At full moon, as seen from the Earth, the Moon lies

a) opposite the Sun
b) 90 degrees east of the Sun
c) 90 degrees west of the sun
d) close to the Sun in the sky

A

a) opposite the Sun

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11
Q

If the Moon rises at 4 am, what is its phase?

a) new
b) waxing crescent
c) waning crescent
d) waxing gibbous
e) waning gibbous

A

c) waning crescent

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12
Q

What causes the Moon’s phases?

a) The Earth’s shadow covers part of the Moon.
b) As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.
c) Depending on where the Moon is in its or- bit, light from the Sun lights up a larger or smaller part of the Moon’s surface.
d) The Earth interferes with the Sun’s rays in a way that depends on where the Moon is in its orbit.
e) None of the above

A

b) As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.

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13
Q

The absorption lines of helium have the same wavelength as its emission lines.

a) true b) false

A

a) true

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14
Q

When a light source moves away from you, the wavelength of the light you see is:

a) longer
b) shorter
c) the same length

A

a) longer

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15
Q
  1. Match each action of an electron in an atom to its corresponding process.

A an electron jumps to a lower energy level
B an electron leaves its atom
C an electron jumps to a higher energy level

and

1 atom is ionized
2 atom absorbs light
3 atom emits light

a) Aand1,Band2,Cand3
b) Aand2,Band1,Cand3
c) Aand2,Band3,Cand1
d) Aand3,Band2,Cand1
e) Aand3,Band1,Cand2

A

e) Aand3,Band1,Cand2

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16
Q

When an electron emits light, it moves

a) closer to the nucleus
b) further from the nucleus

A

a) closer to the nucleus

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17
Q

When an electron emits light, it moves

a) closer to the nucleus
b) further from the nucleus

A

a) closer to the nucleus

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18
Q

An element can be identified by looking at its:

a) spectral lines
b) continuous spectrum
c) temperature
d) gamma-ray burst

A

a) spectral lines

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19
Q

An element can be identified by looking at its:

a) spectral lines
b) continuous spectrum
c) temperature
d) gamma-ray burst

A

a) spectral lines

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20
Q

What kinds of particles comprise the nucleus of an atom?

a) electrons and protons
b) protons and neutrons
c) electrons and neutrons
d) none of these

A

b) protons and neutrons

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21
Q

Human body temperature is about 310 K. At what wavelength is most of the light we emit?

a) radio
b) infrared
c) visible
d) x-ray
e) gamma ray

A

b) infrared

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22
Q

Human body temperature is about 310 K. At what wavelength is most of the light we emit?

a) radio
b) infrared
c) visible
d) x-ray
e) gamma ray

A

b) infrared

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23
Q

A star emits light with a blackbody spectrum and a peak wavelength of 3 × 103 nm. What is the temperature of the star’s surface?

a) 100 K
b) 1,000 K
c) 3,000 K
d) 10,000 K
e) 30,000 K

A

b) 1,000 K

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24
Q

Light of which of the following kinds is observed by earthbound telescopes?

a) radio waves and visible light
b) x-rays and gamma rays
c) gamma rays and radio waves
d) visible light and x-rays

A

a) radio waves and visible light

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25
Q

The main advantage of the Hubble Space Tele- scope compared to telescopes on Earth is:

a) friendly aliens help out when it has problems
b) it avoids atmospheric turbulence
c) it can detect radio waves
d) it can detect sound waves that do not reach the Earth

A

b) it avoids atmospheric turbulence

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26
Q

Why are satellites used to detect x-rays?

a) space-based detectors are more sensitive
b) they avoid atmospheric turbulence
c) x-rays are absorbed by the Earth’s atmosphere
d) to avoid interference from x-ray sources on Earth

A

x-rays are absorbed by the Earth’s atmosphere

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27
Q

Sunspots appear dark because they are hotter than the surrounding gas of the photosphere.

a) True
b) False

A

b) False

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28
Q

About how hot is the Sun’s photosphere?

a) 3K
b) 300 K
c) 3000 K
d) 6000 K
e) 10,000 K

A

d) 6000 K

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29
Q

About how hot is the Sun’s photosphere?

a) 3K
b) 300 K
c) 3000 K
d) 6000 K
e) 10,000 K

A

d) 6000 K

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30
Q

The sun rotates

a) fastest near the equator
b) fastest near the poles
c) with the same speed at all latitudes
d) not at all.

A

a) fastest near the equator

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31
Q

The sun rotates

a) fastest near the equator
b) fastest near the poles
c) with the same speed at all latitudes
d) not at all.

A

a) fastest near the equator

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32
Q

What is the most abundant element in the Sun?

a) hydrogen
b) helium
c) carbon
d) oxygen
e) iron

A

a) hydrogen

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33
Q

The Sun is a stable star in which

a) the rate of fusion equals the rate of fission
b) the rate at which energy is emitted by the core is equal to the rate at which energy is absorbed in the corona
c) radiation and convection balance one an- other
d) gravity balances the force from pressure

A

d) gravity balances the force from pressure

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34
Q

The Sun’s energy is produced by the fusion of

a) hydrogen and oxygen to water
b) carbon to iron
c) helium to carbon
d) oxygen to iron
e) hydrogen to helium

A

hydrogen to helium

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35
Q

Compared to the Sun’s corona, its photosphere is

a) denser and hotter
b) denser and cooler
c) less dense and hotter
d) less dense and cooler

A

b) denser and cooler

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36
Q

When hydrogen fuses to helium, what fraction of its mass changes to energy?

a) 100%
b) 70%
c) 50%
d) 5%
e) 0.7%

A

e) 0.7%

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37
Q

The average temperature is hotter in summer
than winter. This is ultimately caused by

a) the greenhouse effect that warms the Earth by trapping infrared radiation.
b) the fact that the Earth is closer to the Sun in summer.
c) the tilt of the Earth’s axis relative to the Earth’s orbit.
d) the fact that the Sun emits more energy per second in the summer than it does in the winter

A

c) the tilt of the Earth’s axis relative to the Earth’s orbit.

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38
Q

Describe the daily motion of Polaris:

a) It rises due east and sets due west once in every 24-hour period.
b) It stays nearly fixed in the northern sky above our North Pole.
c) It rises due west and sets due east once in every 24-hour period.
d) It moves eastward by slightly less than 1 degree per day.

A

b) It stays nearly fixed in the northern sky above our North Pole.

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39
Q

How many days during each year is the Sun directly over the equator?

a) 1
b) 2
c) 182 or 183
d) 365

A

b) 2

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40
Q

The shortest night in Madison is on

a) the winter solstice
b) the spring equinox
c) the autumn equinox
d) the summer solstice

A

d) the summer solstice

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41
Q
  1. Where on Earth are you if Polaris is on your horizon?

a) north pole
b) south pole
c) Tropic of Cancer
d) Tropic of Capricorn
e) equator

A

e) equator

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42
Q

A rover exploring a planet rolls north from the equator to a point whose latitude is 45 degrees north. If the rover has traveled 1,000 km, what is the circumference of the planet?

a) 450 km
b) 1,000 km
c) 2,000 km
d) 4,000 km
e) 8,000 km

A

e) 8,000 km

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43
Q

If the Moon’s orbit were exactly in the plane of the Earth’s orbit about the Sun, one would expect an eclipse of the Moon to occur about once every

a) week
b) 2 weeks
c) month
d) year
e) never

A

c) month

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44
Q

At full moon, as seen from the Earth, the Moon lies

a) opposite the Sun
b) 90 degrees east of the Sun
c) 90 degrees west of the sun
d) close to the Sun in the sky

A

a) opposite the Sun

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45
Q

There is an eclipse on a day when the Moon rises at 6pm.Is it an eclipse of the Sun or of the Moon?

a) Sun
b) Moon

c) It is not possible to have an eclipse when
the Moon rises at 6 pm

A

b) Moon

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46
Q

If the Moon rises at 4 am, what is its phase?

a) new
b) waxing crescent
c) waning crescent
d) waxing gibbous
e) waning gibbous

A

c) waning crescent

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47
Q

What causes the Moon’s phases?

a) The Earth’s shadow covers part of the Moon.
b) As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.
c) Depending on where the Moon is in its orbit, light from the Sun lights up a larger or smaller part of the Moon’s surface.
d) The Earth interferes with the Sun’s rays in a way that depends on where the Moon is in its orbit.
e) None of the above

A

b) As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.

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48
Q

The absorption lines of helium have the same wavelength as its emission lines.

a) true
b) false

A

a) true

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49
Q

When a light source moves away from you, the wavelength of the light you see is:

a) longer
b) shorter
c) the same length

A

a) longer

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50
Q
  1. Match each action of an electron in an atom to its corresponding process.

A an electron jumps to a lower energy level
B an electron leaves its atom
C an electron jumps to a higher energy level

and

1 atom is ionized
2 atom absorbs light
3 atom emits light

a) Aand1,Band2,Cand3
b) Aand2,Band1,Cand3
c) Aand2,Band3,Cand1
d) Aand3,Band2,Cand1
e) Aand3,Band1,Cand2

A

e) Aand3,Band1,Cand2

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51
Q

When an electron emits light, it moves

a) closer to the nucleus
b) further from the nucleus

A

a) closer to the nucleus

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52
Q

When an object is heated, the light it emits is:

a) brighter and with longer average wave- length
b) dimmer and with longer average wave- length
c) brighter and with shorter average wavelength
d) dimmer and with shorter average wave- length

A

c) brighter and with shorter average wavelength

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53
Q

An element can be identified by looking at its:

a) spectral lines
b) continuous spectrum
c) temperature
d) gamma-ray burst

A

a) spectral lines

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54
Q

Aldebaran is a red star, while the Sun’s peak wavelength is in the green part of the visible spectrum. (The Sun’s blue light is scattered by the air, giving us a blue sky and leaving the Sun looking yellow.) Compared to the Sun’s surface, Aldebaran’s surface is

a) hotter
b) cooler
c) the same
d) there is not enough information given to answer this question

A

b) cooler

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55
Q

What kinds of particles comprise the nucleus of an atom?

a) electrons and protons
b) protons and neutrons
c) electrons and neutrons
d) none of these

A

b) protons and neutrons

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56
Q

Human body temperature is about 310 K. At what wavelength is most of the light we emit?

a) radio
b) infrared
c) visible
d) x-ray
e) gamma ray

A

b) infrared

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57
Q

A star emits light with a blackbody spectrum and a peak wavelength of 3 × 103 nm. What is the temperature of the star’s surface?

a) 100 K
b) 1,000 K
c) 3,000 K
d) 10,000 K
e) 30,000 K

A

b) 1,000 K

58
Q

Light of which of the following kinds is observed by earthbound telescopes?

a) radio waves and visible light b) x-rays and gamma rays
c) gamma rays and radio waves d) visible light and x-rays

A

a) radio waves and visible light

59
Q

The main advantage of the Hubble Space Tele- scope compared to telescopes on Earth is:

a) friendly aliens help out when it has problems
b) it avoids atmospheric turbulence
c) it can detect radio waves
d) it can detect sound waves that do not reach the Earth

A

b) it avoids atmospheric turbulence

60
Q

Why are satellites used to detect x-rays?

a) space-based detectors are more sensitive
b) they avoid atmospheric turbulence
c) x-rays are absorbed by the Earth’s atmosphere
d) to avoid interference from x-ray sources on Earth

A

x-rays are absorbed by the Earth’s atmosphere

61
Q

The Herschel Infrared Space Telescope is stationed far from earth because

a) This increases the telescope’s field of view
b) The telescope is sensitive to electromagnetic interference from terrestrial radio stations
c) Doing so avoids the obscuring effects of dust close to the ground.
d) Earth is a heat source and the telescope must be kept very cold.

A

d) Earth is a heat source and the telescope must be kept very cold.

62
Q

Sunspots appear dark because they are hotter than the surrounding gas of the photosphere.

a) True
b) False

A

b) False

63
Q

About how hot is the Sun’s photosphere?

a) 3K
b) 300 K
c) 3000 K
d) 6000 K
e) 10,000 K

A

d) 6000 K

64
Q

The visible light we see from the Sun comes
from what part of the Sun?

a) photosphere
b) corona
c) chromosphere
d) core

A

a) photosphere

65
Q

The sun rotates

a) fastest near the equator
b) fastest near the poles
c) with the same speed at all latitudes
d) not at all.

A

a) fastest near the equator

66
Q

What is the most abundant element in the Sun?

a) hydrogen
b) helium
c) carbon
d) oxygen
e) iron

A

a) hydrogen

67
Q

The Sun is a stable star in which

a) the rate of fusion equals the rate of fission
b) the rate at which energy is emitted by the core is equal to the rate at which energy is absorbed in the corona
c) radiation and convection balance one an- other
d) gravity balances the force from pressure

A

d) gravity balances the force from pressure

68
Q

The Sun’s energy is produced by the fusion of

a) hydrogen and oxygen to water
b) carbon to iron
c) helium to carbon
d) oxygen to iron
e) hydrogen to helium

A

hydrogen to helium

69
Q

Compared to the Sun’s corona, its photosphere is

a) denser and hotter
b) denser and cooler
c) less dense and hotter
d) less dense and cooler

A

b) denser and cooler

70
Q

When hydrogen fuses to helium, what fraction of its mass changes to energy?

a) 100%
b) 70%
c) 50%
d) 5%
e) 0.7%

A

e) 0.7%

71
Q

Which of the following lists gives the spectral types of stars in order from the type corresponding to stars with the hottest surfaces to the type corresponding to stars with the coolest surfaces?

a) F,B,G,O,M
b) A,B,F,G,O
c) O,B,F,G,M
d) K,M,F,G,B
e) B,G,F,M,K

A

c) O,B,F,G,M

72
Q

Star A appears brighter than star B, as seen from Earth. Therefore, start A must be closer to Earth than star B.

a) True
b) False

A

b) False

73
Q

Stars with cool surfaces can be very luminous
if they are very

a) small
b) hot
c) large
d) close to our solar system

A

c) large

74
Q

Which two of the following need to be mea- sured in order to determine the luminosity of a star?

a) apparent brightness and temperature
b) temperature and mass
c) distance and apparent brightness
d) mass and distance

A

c) distance and apparent

75
Q

Once the luminosity of a star is known, what has to be measured in order to find the star’s radius?

a) parallax angle to find distance
b) color to find distance
c) color to find surface temperature
d) parallax angle to find surface temperature

A

c) color to find surface temperature

76
Q

About what fraction of stars are in binary systems?

a) 1/10
b) 1/2
c) 9/10

A

b) 1/2

77
Q

What two physical characteristics of stars are related by an H-R diagram?

a) mass and luminosity
b) luminosity and surface temperature
c) mass and surface temperature
d) mass and radius
e) luminosity and radius

A

b) luminosity and surface temperature

78
Q

About what fraction of stars are on the main sequence?

a) less than 10%
b) about 50%
c) about 90%

A

c) about 90%

79
Q

If the Sun had a cooler surface, it would be

a) bluer
b) redder
c) there would be no difference in its color

A

b) redder

80
Q

From a distance of 1 parsec, the angular size (radius) of Earth’s orbit would be

a) 1 arc second
b) 1 degree
c) 2 degrees
d) impossible to determine

A

a) 1 arc second

81
Q

The planets Londinium and Bellerophon orbit a star called the White Sun. Londinium is 1 AU from the star, and Bellerophon is 10 AU away. The brightness of light from the White Sun on Londinium is about 100 watt/meter2. What is the brightness of light from the White Sun on Bellerophon?

a) 1 watt/meter2
b) 10 watt/meter2
c) 1000 watt/meter2
d) 10,000 watt/meter2

A

a) 1 watt/meter2

82
Q

Compared to a main-sequence star of type G, a main-sequence star of type B is:

a) hotter and less massive
b) hotter and more massive
c) cooler and less massive
d) cooler and more massive

A

b) hotter and more massive

83
Q

Stars of spectral class M do not show strong lines of hydrogen in their spectra because

a) they contain very little hydrogen
b) their surfaces are so cool that most hydrogen is in the ground state
c) their surfaces are so hot that most hydro- gen is ionized elements
d) the hydrogen lines are swamped by even stronger lines of other elements

A

b) their surfaces are so cool that most hydrogen is in the ground state

84
Q

In the Hertzsprung-Russell diagram shown in the previous questions, which star would have the reddest color? to the Sun?

a) Alnilam
b) Sirius B
c) HR 5337
d) Arcturus
e) Antares

A

e) Antares

85
Q

What type of star is the Sun?

a) A
b) B
c) F
d) G
e) O

A

d) G

86
Q

The average density of the interstellar medium is

a) much denser than earths atmosphere
b) much less dense that the best vacuum on earth
c) about the same density as air ion the peak of Mount Everest
d) zero

A

b) much less dense that the best vacuum on earth

87
Q

What is the most likely explanation for the dark area in the image (taken in the visible spectral range) shown below?

a) It is a region where there are no stars
b) It is a region with lots of dark matter
c) It is a supermassive black hole
d) It is a region with thick dust blocking the starlight coming from behind
e) It is a dark star cluster

A

d) It is a region with thick dust blocking the starlight coming from behind

88
Q

Two clouds of interstellar gas contract to form stars. Suppose that no mass is lost in the con- traction and that when they stop contracting, cloud A is a type A star and cloud K is a type K star. Compared to cloud A, cloud K has

a) the same mass and the same percentage of hydrogen
b) a smaller percentage of hydrogen
c) a larger percentage of hydrogen
d) more mass
e) less mass

A

e) less mass

89
Q

You observe two stars in the sky. Star A is a spectral class O supergiant, star B is a spectral class O white dwarf. What can you say about their temperatures?

a) A is hotter than B
b) B is hotter than A
c) A and B have approximately the same temperature
d) We do not have enough information to de- rive their temperatures.

A

c) A and B have approximately the same temperature

90
Q

When visible light from a star passes through interstellar dust, the light

a) ionizes the dust, which then emits blue and ultraviolet light
b) is dimmed and becomes bluer
c) is dimmed and reddened
d) primarily excites electrons in the silicon atoms of the dust. We observe ultraviolet light when the electrons fall back to their ground state.
e) is Doppler shifted

A

c) is dimmed and reddened

91
Q

Two clouds of interstellar gas contract to form stars. Suppose that no mass is lost in the con- traction and that when they stop contracting, cloud A is a type A star and cloud K is a type K star. What stops the contraction of each star?

a) Cloud A is stopped by fusion of helium to carbon and cloud K is stopped by fusion of hydrogen to helium
b) Cloud K is stopped by fusion of helium to carbon and cloud A is stopped by fusion of hydrogen to helium
c) Both clouds are stopped by fusion of hydrogen to helium
d) Both clouds are stopped by fusion of he- lium to carbon
e) None of these answers is even remotely related to what happens in the formation of stars.

A

c) Both clouds are stopped by fusion of hydrogen to helium

92
Q

A main-sequence star with a mass of 15 times the mass of the Sun has a lifetime that is

a) much longer than the Sun’s.
b) much shorter than the Sun’s.
c) about the same as the Sun’s.

A

b) much shorter than the Sun’s

93
Q

It takes less and less time to fuse heavier and heavier elements inside a high-mass star.

a) True
b) False

A

True

94
Q

Star formation requires a sufficient amount of ……… to begin.

a) Hot gas with millions of degrees K
b) Cold gas with temperatures of tens of degrees K
c) Asteroid collisions
d) Emission from emission nebulae
e) Ionizing radiation

A

b) Cold gas with temperatures of tens of degrees K

95
Q

What is the next stage in the Sun’s evolution?

a) neutron star
b) T-Tauri star
c) white dwarf
d) type F main-sequence star e) red giant

A

e) red giant

96
Q

Most of the nitrogen on Earth was

a) formed in a supernova
b) formed in a star that later exploded in a supernova
c) formed in a planetary nebula
d) formed in a star that then lost its outer envelope in a planetary nebula

A

b) formed in a star that later exploded in a supernova

97
Q

In a core-collapse supernova, the outer part of the core rebounds from the inner, high-density core, destroying the entire outer part of the star.

a) True
b) False

A

a) True

98
Q

A nova is a sudden outburst of light coming from an old main sequence star.

a) True
b) False

A

b) False

99
Q

One billion years from now the Sun will be a

a) red giant
b) main-sequence star
c) white dwarf
d) none of the above

A

b) main-sequence star

100
Q

Match the phases of stellar evolution listed be- low (1-4) to the appropriate energy generating processes (A-D).

1 Contraction of the core and fusion of hy- drogen to helium in a shell
2 Fusion of helium to carbon in the core
3 Contraction of the entire star
4 Fusion of hydrogen to helium in the core

A The energy source for a star just after the helium flash.
B The energy source of a star in its first red- giant stage.
C The energy source of a main sequence star.
D The energy source of a protostar, before it has reached the main sequence.

a) 1andB,2andD,3andC,4andA
b) 1andA,2andB,3andD,4andC
c) 1andD,2andA,3andC,4andB
d) 1andC,2andB,3andA,4andD
e) 1andB,2andA,3andD,4andC

A

e) 1andB,2andA,3andD,4andC

101
Q 
Put the following stages in a star’s evolution in chronological order from first to last:
A contraction of a gas cloud
B main-sequence star
C ejection of a planetary nebula
D first red giant stage
E fusion of helium to carbon in the core

a) C,A,B,E,D
b) A,D,B,E,C
c) B,A,C,E,D
d) A,B,D,E,C
e) A,B,C,D,E

A

d) A,B,D,E,C

102
Q

What is the upper limit on the mass of a white dwarf?

a) 0.08 solar masses
b) 0.5 solar masses
c) 1.4 solar masses
d) 10 solar masses

A

c) 1.4 solar masses

103
Q

Match the descriptions below to their names:

A Type I supernova
B Nova
C Planetary nebula
D Type II supernova

1 The ejected outer part of a star whose core becomes a white dwarf.
2 The explosion that results from hydrogen from a companion star falling onto a white dwarf and suddenly fusing to helium when it gets hot enough to ignite.
3 The explosion that results from the gravitational collapse of the iron core of a massive star when it approaches its upper mass limit.
4 The explosion that results from the gravitational collapse of a white dwarf when it approaches or reaches its upper mass limit.

a) 1andC,2andB,3andD,4andA
b) 1andA,2andB,3andD,4andC
c) 1andD,2andA,3andC,4andB
d) 1andC,2andB,3andA,4andD
e) 1andB,2andA,3andD,4andC

A

a) 1andC, 2andB, 3andD, 4andA

104
Q

What ages does a star cluster have in which all stars have masses similar to or less than the mass of our Sun?

a) A large age of many billions of years
b) A very young age of at most a few millions
of years
c) Each star has a different age, so we can not tell the age of the cluster

A

a) A large age of many billions of years

105
Q

We should expect for galaxies to collide fairly often because

they are large with respect to their separating distances

galaxies contain large amounts of neutral hydrogen

galaxies occur in clusters

a and c above

none of the above

A

a and c above

106
Q

Starburst galaxies, such as Ultraluminous Infrared Galaxies,

contain a large number of very young stars, but very little evidence of gas clouds

contain a large number of very old stars and almost no gas or dust

are often associated with a galaxy that is colliding with another galaxy

are common in rich clusters

are composed of filaments and voids

A

are often associated with a galaxy that is colliding with another galaxy

107
Q

An elliptical galaxy could

evolve into an irregular galaxy when it has used up all its gas and dust

be formed from the collision of spiral galaxies

evolve from a single spiral galaxy when the spiral has used up all of its gas and dust

become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster

A

be formed from the collision of spiral galaxies

108
Q

The Virgo cluster

is the galaxy cluster that contains the Milky Way

is the oldest known cluster of galaxies

is located at the center of the Universe

contains mostly spirals and very few elliptical galaxies

is a rich cluster and the closest cluster of galaxies outside of the Local Group

A

is a rich cluster and the closest cluster of galaxies outside of the Local Group

109
Q

The assumption of isotropy states that

the universe looks the same at all epochs

the universe looks the same from all locations over sufficiently great distances

the universe looks the same in all directions over sufficiently great distances

all of the above

A

the universe looks the same in all directions over sufficiently great distances

110
Q

The cosmic microwave background radiation comes from a time in the evolution of the universe

when protons and neutrons were first formed

when the big bang first began to expand

the inflationary period

when gamma rays had enough energy to destroy nuclei

when electrons began to recombine with nuclei to form atoms

A

when electrons began to recombine with nuclei to form atoms

111
Q

Current evidence suggests that the universe is

flat, infinite, and neither expanding nor contracting

closed, finite, and slowing in its expansion

open, infinite, and slowing in its expansion

open, finite, and accelerating in its expansion

flat, infinite, and accelerating in its expansion

A

flat, infinite, and accelerating in its expansion

112
Q

Which of the following are changing as the universe is expanding?

the laws of physics

the sizes of atoms

the cosmological distances

the diameters of stars and galaxies

A

the cosmological distances

113
Q

Which of the following is NOT a prediction of the standard Big Bang theory that has been successfully verified by observations?

The universe is expanding

The most distant galaxies are redder because they are older

Helium and lithium were made as the universe cooled after the Big Bang.

The early universe was dense and very hot

The most distant galaxies are redder because their light has been stretched during the time it took for the light to reach Earth.

A

The most distant galaxies are redder because they are older

114
Q

Why is it not possible to look all the way back to the Big Bang itself?

Photons are not produced until the stars begin to shine at redshifts of z=20.

From redshifts of z=0 to 100, photons are gravitationally lensed by the dark matter in the universe

At redshifts of z>1000, most of the photons are blocked by large amounts of cold gas and dust

For redshifts of z>1000, photons cannot travel freely because they easily interact with individual protons and electrons in the universe

Photons from the big bang would be so strongly redshifted that we could never detect them

A

For redshifts of z>1000, photons cannot travel freely because they easily interact with individual protons and electrons in the universe

115
Q

Does the temperature of the cosmic background radiation by itself tell us anything significant about the age of the universe?

Yes, since it was produced at redshift of approximately 1,000.

No, we still need to know the Hubble constant to know the Universe’s age

No, the temperature does not, but the magnitude of temperature variations in the CMB does tell us the age

No, the CMB formed at a wide variety of times and gives no information on the age o the whole universe.

A

No, we still need to know the Hubble constant to know the Universe’s age

116
Q

What is the celestial sphere?

A

The sky has the appearance of a sphere, and at night it looks like the sphere rotates, with all of the stars moving as if the sphere were rotating. The name given to this imaginary sphere is the celestial sphere

This is because the Earth really rotates once a day from west to east: counterclockwise, looking down at the north pole.

117
Q

The ____________Pole and _________ Pole are the points on the celestial sphere directly over the Earth’s North and South poles.

A

North Celestial

South Celestial Pole

118
Q

The seasons are caused by the _________. And the two effect of this are what?

A

The seasons are caused by the tilt of the Earth’s axis. The tilt has
two effects:

  1. Sunlight is more direct in the summer. In our summer, the
    northern hemisphere is tilted toward the Sun, in winter it is
    tilted away from the Sun.
  2. The Sun is up longer in summer than in winter.
119
Q

Atoms ______and_____________ a discrete spectrum of light

A

Atoms emit and absorb a discrete spectrum of light

120
Q

Hydrogen can turn into helium, and when it does, _____% of its mass changes to energy, and that energy powers _______.

A

Hydrogen can turn into helium, and when it does, 0.7% of its mass changes to energy, and that energy powers the Sun

121
Q

Speed of protons depend on temperature, and temperature of at least 10 million K required for fusion: only in center______ and most other _______.

A

Speed of protons depend on temperature, and temperature of at least 10 million K required for fusion: only in center of Sun and most other stars

122
Q

The classification of a star is its spectral type.

Ordered from hottest to coolest, the spectral types are:

A

O, B, A, F, G, K, M (L, T)
(Use the mnemonic Oh, Be A Fine Guy/Girl Kiss Me, or make up your own!)

● O stars are hottest with surface temperature > 25,000 K.
● G stars (like the Sun) have surface temperature of
approximately 6000 K.
● M stars are coolest (Betelgeuse for example) with surface
temperatures approximately 3000 K.

123
Q

The H-R diagram plots luminosity versus surface temperature
More than _______% of all stars lie on the main sequence.
The ________ stars on the main sequence are also the brightest stars, and the dimmest are also the

A

90% and hottest

124
Q

A star similar to the Sun spends its life where?

A

On the main sequence, and then a shorter and shorter amount of time in each phase until it cools as a white dwarf.

125
Q

Stars like the sun go through these phases:

A
  1. Main sequence
  2. Red giant phase
  3. Helium flash
  4. Asymptotic Giant
    Phase
  5. Planetary Nebula
  6. White Dwarf
126
Q

What is the gas in the ISM

A

Gas in the ISM is mostly hydrogen. It is in three phases:
● Cold (10-100s K)
● Warm (around 8000 K) ● Hot (106 K)
Most of the volume is hot, but hot gas is very diffuse – most of the gas is warm or cold. This cold gas is important because it is found in clouds that form stars. Cold gas clouds are what stars come from

127
Q

Star formation - Stage 2 and 3: Cloud fragmentation and core collapse

A

The cloud collapses due to its own gravity
The collapsing cloud fragments into lots of tiny little pieces, called cores – all of which continue to contract and build mass from infalling gas.

128
Q

What is a protostar?

A

Stage 4: The protostar
Because a protostar is star-like, we can put it on the HR diagram. Notice that it is brighter and cooler than the sun, which means that it is very, very big at this stage!
Most of the power output is still generated by gravitational collapse and compression of the gas.

129
Q

What is stage 5 protostellar evolution?

A

As the protostar contracts, it heats up, but gets dimmer!! This is because the star is getting smaller
During this phase, many protostars give off jets of gas – these are called Herbig-Haro objects
Eventually nuclear fusion starts up and the protostar becomes a star

130
Q

What is Hydrostatic balance

A

Recall that stars are a balance between pressure pushing stuff out and gravity pulling stuff in.
Because stars are constantly losing energy, they would contract if it were not for a heat source (nuclear fusion) in the center.

131
Q

Up the Red Giant Branch

A

At first the star cools with the luminosity staying roughly constant—core contraction (stage 8).
Later, hydrogen shell burning makes the star expand (stage 9)

132
Q

What are white dwarfs?

A

White dwarfs
The star burns so brightly that it sheds a planetary nebula—gas that travels away from the star (12).
Once the star runs completely out of nuclear fuel what remains of the star contracts and forms a white dwarf (13).
The star cools eventually becoming a black dwarf, too small and faint to see (14).

133
Q

What are the 6 phases a star like the sun goes through

A 
Stars like the sun go through these phases:
1. Main sequence
2. Red giant phase
3. Helium flash
4. Asymptotic Giant
Phase
5. Planetary Nebula
6. White Dwarf
134
Q

What is a CMB map?

A

The CMB can be used to study the temperature of the universe. This was done since ~20 years ago using satellites.
To reveal small fine structure, we first need to subtract the constant, global temperature and the dipole moment (caused by doppler shift of the signal as the sun moves relative to the CMB).

135
Q

Makeup of Universe:

A

70% DE, 25% DM 4% Elements

136
Q

Evidence for Dark matter:

A

-Rotation Curve, Cluster member velocities, Cluster gravitational lensing

137
Q

Large scale structure:

large scale distribution is clumpy and filamentary, known through large scale redshift surveys of thousands of galaxies

A

biggest structures are ~200 Mpc (1Mpc to Andromeda)

138
Q

-Universe is homoegenous and isotropic

A

homoegenous and isotropic

139
Q
  • Recombination after 300,000 years which released the CMB

- The CMB is the _____________

A

blackbody radiation of the universe

140
Q

-Age of Universe:

A

1/H0, most distant galaxies, oldest stars are 10-13 Gyrs

141
Q

-The universe is dominated by

A

dark energy and will expand forever.

-Inflation solves horizon problem

142
Q

-Early universe: Different particles when T is very large, first 30 minutes big bang ___________.

A

nucleosynthesis

Astronomy (4 decks)

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