Astronomy 101 Rio Salado

Front 1

The visible "surface" of the Sun is called the

Back 1

Photosphere

Front 2

The highest temperature in the solar atmosphere is found in

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The corona

Front 3

What is the visible evidence of overturning gases (convection) in the upper layer of the Sun's interior?

Back 3

The granular appearance (granules)

Front 4

Sunspots are cooler than the surrounding photosphere because

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The strong magnetic field inhibits the currents of hot gas rising from below.

Front 5

It appears that the differential rotation of the Sun winds up the magnetic fields. This is useful in explaining

Back 5

The sunspot cycle

Front 6

When sunspots increase in number, solar activity, such as the number of solar flares

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Increases

Front 7

The Sun is supported against the crushing force of its own gravity by

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Gas pressure

Front 8

The Sun produces its energy from

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Fusion of hydrogen into helium

Front 9

The apparent shift in the position of an object, such as a star, can be used to measure distance is

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Parallax

Front 10

The H-R diagram compares the intrinsic brightness of a star to its

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Temperature or color

Front 11

In the H-R diagram, 90% of all stars fall

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On the main sequence

Front 12

Where on the H-R diagram are the extremely bright, hot, and massive stars found?

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The upper left corner of the main sequence

Front 13

Where on the H-R diagram are the extremely bright, but cool stars?

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The red giant branch

Front 14

Where on the H-R diagram are the very small, but very hot stars?

Back 14

The white dwarf branch

Front 15

Which of the following star magnitudes is the brightest?

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???

Front 16

A star that is cool and very luminous must have

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A very large radius

Front 17

By observing the orbital periods of binary stars, astronomers can determine what property of stars?

Back 17

Mass

Front 18

Spectral class is which kind of sequence?

Back 18

Temperature

Front 19

Composition of a star can be measured from

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Its pattern of spectral lines

Front 20

Motion of a star away from or toward Earth can be measured by

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The shift in its spectral lines

Front 21

The element that makes up most of the mass of interstellar medium is

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Hydrogen

Front 22

To collapse into stars, an interstellar cloud must be

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Cold and dense

Front 23

The time a protostar takes to contract from a cool interstellar gas cloud to a main sequence star depends on its

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Mass

Front 24

Which of the following causes protostars to heat?

Back 24

Increased pressure from the weight of the collapse

Front 25

Nuclear fusion of hydrogen into helium occurs in the cores of

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Main sequence stars

Front 26

The mass-luminosity relation exists because

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Stars support their weight by making energy.

Front 27

When the core of a star is depleted of hydrogen causing the core to shrink and become hotter, the star itself becomes

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Larger and cooler

Front 28

The next stage in the evolution of the Sun is

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A red giant

Front 29

Main sequence stars of which classification spend the most time on the Hertzsprung-Russell diagram?

Back 29

M

Front 30

A turn-off point on the H-R diagram of a star cluster is used to determine the

Back 30

The age of the cluster

Front 31

What kinds of objects lie in the disk of the Milky Way galaxy?

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All of the above

Front 32

How does the interstellar medium obscure your view of most of the galaxy?

Back 32

It absorbs visible, ultraviolet, and some infrared light.

Front 33

All the iron on Earth originated from

Back 33

Nuclear fusion within the cores of high-mass stars

Front 34

What is the most common form of gas in the interstellar medium?

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Atomic hydrogen

Front 35

Where do most dust grains form?

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In the winds of red giant stars

Front 36

Suppose you read somewhere that 10% of the matter in the Milky Way is in the form of dust grains. Should you be surprised? If so, why?

Back 36

The 10% figure cannot be correct, because dust grains are solid but only about 2% of the matter in the galaxy is made of anything besides hydrogen and helium.

Front 37

How do you learn about what is going on in the center of the Milky Way galaxy?

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You cannot see the galactic center with visible or ultraviolet light, but radio and X-rays from the center can be detected.

Front 38

How do you know that there is much more mass in the halo of the galaxy than in the disk?

Back 38

Stars in the outskirts of the Milky Way orbit the galaxy at much higher speeds than you would expect if all the mass were concentrated in the disk.

Front 39

Why do astronomers believe that 90% of the mass of the Milky Way is in the form of dark matter?

Back 39

The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.

Front 40

Compared with stars in the disk, the orbits of stars in the halo

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Are elliptical, with random orientation

Front 41

Compared with the Sun, most stars in the halo are

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Old, red, dim, and have fewer heavy elements

Front 42

How does the interstellar medium affect your view of most of the galaxy?

Back 42

It prevents you from seeing most of the galactic disk with visible, ultraviolet, and some infrared light.

Front 43

The image of the galaxy in radio emission from CO, mapping the distribution of molecular clouds, is closest to the image of the galaxy in

Back 43

Infrared emission from interstellar dust grains

Front 44

Suppose a scientist holds a press conference, at which he claims that 10% of the matter in the Milky Way is in the form of dust grains. In light of what you think you now know, does his claim seem reasonable? Why or why not?

Back 44

The 10% figure seems far too high because there are not enough of the kinds of elements that can take solid form in the galaxy.

Front 45

Which of the following does not accurately describe what is observed toward the Galactic center?

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At optical wavelengths, you see a cluster of old, red stars.

Front 46

What evidence supports the theory that there is a black hole at the center of this galaxy?

Back 46

The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about one parsec across.

Front 47

What is Sgr A*?

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A source of bright radio emission in the center of the galaxy

Front 48

Suppose you want to observe and study the radiation from gas inside an interstellar bubble. Which of the following observatories will be most useful?

Back 48

The Chandra X-ray Observatory

Front 49

How should you expect that the interstellar medium of the Milky Way to be different in 50 billion years?

Back 49

The total amount of gas will be much less than it is today.

Front 50

The most common form of gas in the disk of the Milky Way galaxy is

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Atomic hydrogen gas

Front 51

All the following types of objects are found almost exclusively in the disk, rather than halo of the Milky Way except:

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Globular clusters

Front 52

Red and orange stars are found evenly spread throughout the galactic disk, but blue stars are typically found

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Only near star-forming regions

Front 53

Most nearby stars move relative to the Sun at speeds below about 30 km/s. Suppose you observe a Suppose you discover a nearby star that is moving much faster than this (say, 300 km/s). Which of the following is a likely explanation for its high speed?

Back 53

It is probably a halo star, which is currently passing through the disk.

Front 54

Why do scientists believe that most of the mass of the Milky Way is in the form of dark matter?

Back 54

The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.

Front 55

If you were to take a voyage across the Milky Way, what kind of material would you spend most of your time in?

Back 55

Warm, rarefied clouds of atomic hydrogen

Front 56

What do astronomers consider heavy elements?

Back 56

All elements besides hydrogen and helium

Front 57

Which of the following statements is not true of the object known as Sgr A* in the center of this Galaxy?

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Its accretion disk is so large that it shines brightly in visible light.

Front 58

Why are spiral arms bright?

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Because they contain more hot young stars than other parts of the disk

Front 59

Approximately how long does it take the Sun to orbit the Milky Way Galaxy?

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230 million years

Front 60

What produces the 21-cm line that is used to map out the Milky Way Galaxy?

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Atomic hydrogen

Front 61

Suppose that you look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?

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The one that is farthest away

Front 62

Which of the following types of galaxies are most spherical in shape?

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Ellipticals

Front 63

Which of the following types of galaxies are reddest in color?

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Ellipticals

Front 64

Compared to spiral galaxies, elliptical galaxies are

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Redder and rounder

Front 65

The disk component of a spiral galaxy includes which of the following parts?

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Spiral arms

Front 66

Which of the following is true about irregular galaxies?

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They were more common when the universe was younger.

Front 67

What two quantities did Edwin Hubble compare to discover the expansion of the universe?

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Velocity and distance

Front 68

What is the most accurate way to determine the distance to a nearby star?

Back 68

Stellar parallax

Front 69

Which of the following gives the two main assumptions of theoretical models of galaxy evolution?

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Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.

Front 70

What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy?

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All of the above

Front 71

What evidence suggests that the Milky Way contains dark matter?

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You observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at unexpectedly high speeds, higher speeds than they would have if they felt only the gravitational attraction from objects that you can see.

Front 72

If there is no dark matter in the Milky Way Galaxy, what is the best alternative explanation for the observations?

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The current understanding of gravity is not correct for galaxy-size scales.

Front 73

How do you determine the amount of dark matter in elliptical galaxies?

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You measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit.

Front 74

Which of the following is not evidence for dark matter?

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The expansion of the universe

Front 75

Why isn't space expanding within systems such as this solar system or the Milky Way?

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Their gravity is strong enough to hold them together against the expansion of the universe.

Front 76

If all the "dark matter" in the universe were to be instantaneously removed, which of the following would not happen?

Back 76

The solar system would fly apart.

Front 77

Which model of the universe gives the youngest age for its present size?

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A recollapsing universe

Front 78

What does the universe look like on very large scales?

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Galaxies appear to be distributed in chains and sheets that surround great voids

Front 79

Which of the following is not one of the three main strategies used to measure the masses of galaxy clusters?

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Measuring the temperatures of stars in the halos of the galaxies

Front 80

Which of the following statements best summarizes what studies of the masses of individual galaxies and of clusters of galaxies say about dark matter?

Back 80

Dark matter is the dominant form of mass in both clusters and individual galaxies.

Front 81

The Planck era refers to the time

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Before the Planck time

Front 82

Why can't current theories describe what happened during the Planck era?

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Scientists do not yet have a theory that links quantum mechanics and general relativity.

Front 83

What is meant by inflation?

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A sudden expansion of the universe after the strong force froze out from the GUT force

Front 84

What direct evidence exists that the weak and electromagnetic forces were once unified as a single electroweak force?

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Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.

Front 85

What is postulated to have caused a sudden inflation of the early universe?

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The "freezing out" of the strong force from the GUT force

Front 86

Olbers' paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question?

Back 86

Why is the sky dark at night?

Front 87

The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?

Back 87

The first theory predicts the existence of and the specific characteristics of the observed cosmic microwave background while the second theory correctly predicts the observed overall chemical composition of the universe.

Front 88

Which statement about the cosmic microwave background is not true?

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It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.

Front 89

Based on the Big Bang theory, what do observations of the cosmic microwave background and of chemical abundances in the universe suggest about dark matter?

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Much of the dark matter must be made of non-ordinary (nonbaryonic) matter, such as WIMPs.

Front 90

Which of the following observations cannot be explained by the Big Bang theory unless you assume that an episode of inflation occurred?

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The fact that the temperature of the cosmic microwave background is almost the same everywhere