Deck 16: A Universe of Galaxies

Question 1

The distinguishing feature of a starburst galaxy is _ .

A)a very large luminosity compared to the total luminosity of the Milky Way
B)a rate of star formation that may be 100 or more times greater than that in the Milky Way
C)strong radio emission from "lobes" of material well outside the visible boundaries of the galaxy
D)the presence of an unusually large number of binary star systems containing X- ray bursters

Answer 1

B

Question 2

Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?

A)The more frequent collisions between particles randomize the particle orbits.
B)The higher density of gas has a stronger force of gravity, and therefore the cloud collapses more quickly.
C)The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.
D)The force of gravity can pull the material into a more spherical shape.
E)The thickness of the dense cloud prevents a disk from forming.

Answer 2

C

Question 3

Which of the following is true about irregular galaxies?

A)They have significant spheroidal component.
B)They are composed solely of old stars.
C)They have well defined spiral arms.
D)They have reddish colors.
E)They were more common when the universe was younger.

Answer 3

E

Question 4

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

A)radar ranging
B)Cepheid variables
C)main sequence fitting
D)stellar parallax
E)Hubble's law

Question 5

The most basic difference between elliptical galaxies and spiral galaxies is that .

A)elliptical galaxies are very old and spiral galaxies are very young
B)elliptical galaxies lack anything resembling the disk of a spiral galaxy
C)elliptical galaxies lack anything resembling the halo of a spiral galaxy
D)elliptical galaxies have a spheroidal component (of stars distributed spherically about the galactic center), and spiral galaxies do not

Question 6

Which types of galaxies have a clearly defined disk component?

A)spirals and lenticulars
B)ellipticals only
C)irregulars only
D)spirals only
E)lenticulars only

Question 7

In a uniformly expanding universe, which statement best describes the situation as viewed from an observer in Galaxy C (not the Milky Way Galaxy)?

A)Galaxy C observer sees some galaxies moving away, some moving towards itself.
B)Galaxy C observer sees all galaxies moving away from the Milky Way Galaxy.
C)Galaxy C observer sees all other galaxies moving away from itself.

Question 8

The observed relationship between the masses of central black holes and the bulge masses of galaxies implies that .

A)quasars were more common 10 billion years ago than they are today
B)the black hole will eventually suck in the rest of the galaxy
C)galaxy formation and supermassive black hole formation must be related somehow
D)the biggest galaxies have the most luminous quasars

Question 9

Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?

A)It will allow us to determine the mass of the galaxy.
B)Under the rules of the International Astronomical Union, we will be entitled to naming rights for the galaxy.
C)It will allow us to calculate the rotation rate of the galaxy.
D)We can learn the distance to the galaxy.

Question 10

One possible explanation for a galaxy's type invokes the angular momentum of the protogalactic cloud from which it formed. Suppose a galaxy forms from a protogalactic cloud with a lot of angular momentum. Assuming its type has not changed due to other interactions, we'd expect this galaxy to be .

A)a torn and incoherent galaxy
B)a spiral galaxy
C)an elliptical galaxy
D)an irregular galaxy

Question 11

Why are collisions between galaxies more likely than collisions between stars within a galaxy?

A)Relative to their sizes, galaxies are closer together than stars.
B)Galaxies are much larger than stars.
C)Galaxies have higher redshifts than stars.
D)Galaxies travel through space much faster than stars.

Question 12

This figure shows the Cepheid period- luminosity relation. A Cepheid star with a period of 30 days has the same apparent brightness as a nearby G2 star. How many times further away is the Cepheid star?

A)The Cepheid star is 100 times further away than the nearby G2 star.
B)The Cepheid star is 10,000 times further away than the nearby G2 star.
C)The Cepheid star is 10 times further away than the nearby G2 star.
D)The Cepheid star is actually a factor of 10 times closer than the nearby G2 star.

Question 13

A quasar's spectrum is hugely redshifted. What does this large redshift tells us about the quasar?

A)the distance to the quasar
B)the size of the quasar's central, supermassive black hole
C)the type of host galaxy in which the quasar resides
D)the composition of the quasar

Question 14

What is the major difference between an elliptical galaxy and a spiral galaxy?

A)Elliptical galaxies are not as big as spiral galaxies.
B)A spiral galaxy contains mostly younger stars.
C)An elliptical galaxy lacks a disk component.
D)There are no dwarf spiral galaxies, but there are dwarf ellipticals.
E)A spiral galaxy has a spherical halo.

Question 15

What can be inferred about the distance traveled by the blob of plasma shown moving in this figure at almost the speed of light?

A)It moved several light years between 1991 and 1997.
B)It could only have moved a small fraction of a light year between 1991 and 1997.
C)There is not enough information to tell anything about the distance traveled by the plasma.

Question 16

In this picture, we are seeing light from the circled elliptical galaxy (HUDF- JD2)from when the universe was only about 800 million years old. The spiral galaxy below it is much closer. Why does HUDF- JD2 appear a deep red, compared to the whitish color of the nearby spiral?

A)Thick dust from active star formation blocks all the blue light, only letting red light escape.
B)At such a large distance, all the light emitted by it is very redshifted.
C)Even at this young age, the galaxy contains few high mass blue stars.
D)A and B
E)B and C

Question 17

Why should galaxy collisions have been more common in the past than they are today?

A)Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars and light.
B)Galaxies were much bigger in the past because they had not contracted completely.
C)Galaxies were closer together in the past because the universe was smaller.
D)Galaxy collisions shouldn't have been more common in the past than they are now.
E)Galaxies were more active in the past and therefore would have collided with each other more frequently.

Question 18

According to current understanding, what is a quasar?

A)any object with an extremely large redshift
B)an active galactic nucleus that is particularly bright
C)a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster
D)a galaxy with an unusually high rate of star formation

Question 19

Current estimates place the age of the universe at about .

A)10 million years
B)10 billion years
C)4 1/2 billion years
D)14 billion years

Question 20

Which characteristic is not generally true of a starburst galaxy?

A)Its rate of star formation is many times higher than the rate of star formation in the Milky Way.
B)Supernovae occur so frequently that their effects combine to drive a galactic wind that blows material into intergalactic space.
C)The observed features that cause us to classify it as a "starburst" must be only temporary phenomena in the galaxy's history.
D)The observed features of the starburst are thought to be caused by the presence of a supermassive black hole in the galaxy's center.

Question 21

Although the entire universe may be much larger than our observable universe, we can see only within our observable universe. The "boundary" of our observable universe is called .

A)the lookback time
B)the cosmological horizon
C)the Big Bang
D)the Hubble Deep Field

Question 22

Which types of galaxies have a clearly defined spheroidal component?

A)lenticulars only
B)irregulars only
C)ellipticals only
D)spirals only
E)all but irregulars

Question 23

Which of the following statements is not an assumption used in models of galaxy formation?

A)The universe started out filled almost uniformly with hydrogen and helium.
B)Gas contracted to form the disks of galaxies before any stars were born.
C)The universe is expanding.
D)Some regions in the universe were slightly more dense than others.

Question 24

Which of the following is a consequence of Hubble's Law?

A)More distant galaxies appear younger.
B)All galaxies are moving away from us equally fast.
C)The more distant a galaxy is from us, the faster it moves away from us.
D)The Big Bang
E)The closer a galaxy is to us, the faster it moves away from us.

Question 25

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

A)ellipticals
B)irregulars
C)lenticulars
D)spirals

Question 26

Given that white dwarf supernovae are such good standard candles, why don't we use them to measure the distance to all galaxies?

A)We cannot see them beyond a distance of about 100 million light- years.
B)They are rare events, so we have observed them in only a tiny fraction of all galaxies.
C)They can occur only in spiral galaxies, not elliptical galaxies.
D)We would, but we don't have enough telescopes.

Question 27

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?

A)He was the first person ever to look through a telescope at the object we now call the Andromeda Galaxy.
B)By observing individual Cepheid variable stars in Andromeda and applying the period- luminosity relation
C)He was able to measure the parallax of the Andromeda Galaxy.
D)He found that the universe is expanding, and therefore concluded that Andromeda must lie outside our own galaxy.

Question 28

A standard candle is _ .

A)another name for a main- sequence star
B)another name for a barred- spiral galaxy
C)a light source of known luminosity
D)a 7- cm- long wax candle

Question 29

Use the graph above showing data for the brightest galaxies in clusters of galaxies to answer the following question. You find a cluster of galaxies, but you do not know how far away it is. The brightest galaxy's infrared color is 0.65. Given the data for brightest galaxies in the graph above, your best estimate for the distance is

A)2)5 × 109 (2.5 billion)light years.
B)1 × 109 (1 billion)light years.
C)4 × 109 (4 billion)light years.
D)It is impossible to say since there are exceptions.

Question 30

Based on the number of galaxies visible in the Hubble Deep Field (Figure 16.1 in your textbook), the estimated number of galaxies in our observable universe is about .

A)Infinity
B)100 million
C)50,000
D)100 billion

Question 31

Most large galaxies in the universe are

A)spiral or lenticular.
B)irregular.
C)elliptical.
D)abnormal.

Question 32

Suppose that we 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?

A)the one that is bluest in color
B)the one that is reddest in color
C)the one that is closest to us
D)the one that is farthest away
E)the one that appears smallest in size

Question 33

How was Edwin Hubble able to use his discovery of Cepheids in Andromeda to prove that the "spiral nebulae" were actually galaxies external to the Milky Way?

A)He measured the parallaxes of the Cepheids in Andromeda to determine their distances. He showed that Andromeda was far outside the Milky Way Galaxy.
B)As a Cepheid is a type of luminous galaxy, Hubble's discovery of Cepheids in Andromeda proved that it was a separate galaxy from the Milky Way.
C)From the period- luminosity relation for Cepheids, he was able to determine the distance to Andromeda. He showed that it was far outside the Milky Way Galaxy.
D)There are no Cepheids in the Milky Way, so his discovery proved that Andromeda had to be in another galaxy.
E)He used main- sequence fitting to determine the distances to the Cepheids. He showed that Andromeda was far outside the Milky Way Galaxy.

Question 34

How did Edwin Hubble measure the distance to the Andromeda Galaxy?

A)He applied the period- luminosity relation to Cepheid variables in Andromeda.
B)He measured its parallax.
C)He detected white dwarf supernovae in Andromeda.
D)He applied main- sequence fitting to star clusters in Andromeda.
E)He measured its redshift and applied Hubble's Law.

Question 35

I observe a galaxy that is 100 million light years away. Which of the following do I see?

A)the light from the galaxy as it is today, and it is redshifted
B)the light from the galaxy as it was 100 million years ago, and it is redshifted
C)the light from the galaxy as it is today, and it is blueshifted
D)the light from the galaxy as it was 100 million years ago, and it is blueshifted
E)Nothing: the galaxy lies beyond the cosmological horizon.

Question 36

Which statement below correctly describes the relationship between expansion rate and age for the universe?

A)The faster the rate of expansion, the older the age of the universe.
B)The faster the rate of expansion, the younger the age of the universe.
C)Age is independent of the expansion rate.

Question 37

What is main- sequence fitting?

A)a way of forcing stars to fit into a standard main sequence, even when they have some unusual characteristics
B)a method for determining the age of a star cluster
C)a method for determining the distance to a star cluster by assuming that its main sequence should line up with the main sequence on a standard H- R diagram
D)the way we construct an H- R diagram by plotting the surface temperatures and luminosities of stars

Question 38

Why can't we see past the cosmological horizon?

A)Beyond the cosmological horizon, we are looking back to a time before the universe had formed.
B)We do not have detectors sensitive enough.
C)We do not have telescopes big enough.
D)The cosmological horizon is infinitely far away, and we can't see to infinity.
E)The universe extends only to this horizon.

Question 39

Suppose we observe a source of X- rays that varies substantially in brightness over a period of a few days. What can we conclude?

A)The X- ray source must have a strong, rapidly varying magnetic field.
B)We must be seeing the rapid orbit of two stars in a binary system.
C)The X- ray source must be a quasar.
D)The X- ray source must contain a black hole with an accretion disk.
E)The X- ray source can be no more than a few light- days in diameter.

Question 40

Interactions among galaxies also are thought to influence a galaxy's type in at least some cases. Which of the following does not support the idea that interactions can shape galaxies?

A)the fact that more distant galaxies have larger redshifts
B)the fact that galaxies with distorted appearances are more common at great distances than nearby
C)computer modeling of collisions between galaxies
D)the presence of features, such as "tails" extending out of galaxies, bridges between galaxies, and rings of stars around galaxies

Question 41

What evidence tells us that quasars are the centers of distant galaxies?

A)Images and spectra show quasars to be embedded at the centers of distant galaxies.
B)Rapid variations in quasar luminosity tell us that they must be quite small in size.
C)All quasars have large redshifts.
D)Quasars are extremely luminous.

Question 42

According to the theory that active galactic nuclei are powered by supermassive black holes, the energy released as light comes from .

A)gravitational potential energy released by matter that is falling toward the black hole
B)jets emerging from the accretion disk
C)nuclear fusion in the accretion disk surrounding the black hole
D)matter- antimatter annihilation occurring just outside the event horizon of the black hole

Question 43

Based on current estimates of the value of Hubble's constant, how old is the universe?

A)12 to 15 billion years old
B)more than 20 billion years old
C)15 to 20 billion years old
D)4 to 8 billion years old
E)8 to 12 billion years old

Question 44

How is the energy that powers radio galaxies, quasars, and other active galactic nuclei produced?

A)by matter that has been converted to pure energy by interacting with the jets shot out by a central black hole
B)by matter- antimatter annihilation near a central black hole
C)by nuclear fusion near a central black hole
D)by magnetic fields that trap and accelerate charged particles, which then radiate large amounts of energy
E)by gravity, which converts the potential energy of matter falling toward a central black hole into kinetic energy, which is then converted to thermal energy by collisions among the particles of matter

Question 45

What does Hubble's law tell us?

A)For every force, there is an equal and opposite reaction force.
B)The faster a spiral galaxy's rotation speed, the more luminous it is.
C)The more distant a galaxy, the faster it is moving away from us.
D)The longer the period of a Cepheid variable, the greater its luminosity.

Question 46

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

A)the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies
B)observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies
C)observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy
D)observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies
E)all of the above

Question 47

If we say that a galaxy has a lookback time of 1 billion years, we mean that .

A)its light traveled through space for 1 billion years to reach us
B)it was 1 billion light- years away when the light left the galaxy
C)it is now 1 billion light- years away
D)it is 400 million years old

Question 48

We can study how galaxies evolve because .

A)we can watch as they interact in real time
B)we are really smart astronomers
C)the farther away we look, the further back in time we see
D)galaxies are transparent to visible light

Question 49

Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy?

A)a very massive cloud with any density and a lot of angular momentum
B)a dense cloud with quite a bit of angular momentum
C)a low- density cloud with quite a bit of angular momentum
D)a dense cloud with very little angular momentum
E)a very low- density cloud with very little angular momentum

Question 50

Which of the following is not a good reason why white- dwarf supernovae are good standard candles for distance measurements?

A)White- dwarf supernovae are so bright that they can be detected even in very distant galaxies.
B)White- dwarf supernovae occur only among young and extremely bright stars.
C)White- dwarf supernovae are common enough that we detect several every year.
D)All white- dwarf supernovae have similar light curves, which makes them easy to distinguish from massive- star supernovae.
E)All white- dwarf supernovae involve the explosion of stars of nearly the same mass.

Question 51

What two observable properties of a Cepheid variable are directly related to one another?

A)its mass and its distance
B)the period between its peaks of brightness and its distance
C)the period between its peaks of brightness and its luminosity
D)its luminosity and its mass

Question 52

Which of the following features is not a feature of central dominant galaxies?

A)They are often spiral galaxies.
B)They often have multiple galactic nuclei near their centers.
C)They are thought to form by the merger of several smaller galaxies.
D)They're found in clusters of galaxies.

Question 53

Telescopes designed to study the earliest stages in galactic lives should be optimized for observations in .

A)infrared light
B)radio waves
C)X- rays
D)visible light

Question 54

Scale the Milky Way down to the size of a compact disc. Which of the following best describes the size, shape, and distance of the Andromeda Galaxy on the same scale?

A)a pecan nut about 1 centimeter away
B)a grapefruit about 1 kilometer away
C)a compact disk about the length of a football field away
D)a grapefruit a few meters away
E)a compact disk a few meters away

Question 55

Why can't we see past the cosmological horizon?

A)Beyond the cosmological horizon, we would be looking back to a time before the universe was born.
B)Every galaxy in the entire universe (not just the observable universe)exists within the cosmological horizon, so there's nothing to see beyond it.
C)The cosmological horizon is infinitely far away, and we can't see to infinity.
D)We do not have big enough telescopes.

Question 56

What is a Cepheid variable?

A)a bright source of variable X- ray emission, thought to harbor a supermassive black hole
B)a main- sequence star of spectral type B5
C)a type of galaxy that varies in its light output
D)a type of very luminous star that makes an excellent standard candle

Question 57

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

A)Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.
B)The beginning of the universe is modeled after a supernova explosion, and all elements were produced by this exploding star.
C)Hydrogen and helium filled all of space, and the entire universe had exactly the same density everywhere.
D)The universe has always been expanding, and denser areas contracted to form the first stars.
E)The universe was composed originally only of hydrogen, and all the other elements came from stars.

Question 58

Use the graph above showing data for the brightest galaxies in clusters of galaxies to answer the following question. If new studies show that the exceptions are a class of galaxies with extraordinarily bright centers, which conclusion is not justified based on the plot and the findings of these new studies?

A)Bright nuclei were more common long ago, since the light from more distant galaxies has been traveling much longer.
B)Bright nuclei are caused by supermassive black holes surrounded by hot gas.
C)Bright nuclei are more common in cluster galaxies that are farther away.
D)Galaxies appear redder the farther away they are.

Question 59

Suppose we observe a source of X- rays that varies substantially in brightness over a period of a few days. What can we conclude?

A)The X- ray source must have a strong, rapidly varying magnetic field.
B)The X- ray source is a quasar.
C)The X- ray source contains a black hole with an accretion disk.
D)The X- ray source is no more than a few light- days in diameter.

Question 60

All of the following observations are real. Which one does not support the theory that active galactic nuclei are powered by accretion disks around massive black holes?

A)The most luminous active galactic nuclei have huge redshifts.
B)Spectra of active galactic nuclei show that clouds of gas are orbiting a central object at very high speed.
C)X- ray emission from active galactic nuclei can vary significantly in times as short as a few days.
D)The total luminosity of an active galactic nucleus can be as high as about 10 billion times that of the Sun.

Question 61

Why is the Hyades Cluster important for building up a catalog of the true luminosities of main- sequence stars?

A)It is an extremely bright star cluster.
B)It is an old globular cluster whose age we can determine very accurately by measuring its main- sequence turn- off point.
C)It contains many Cepheid variable stars that can be used to determine its distance.
D)It is close enough to us that the distance to its stars can be found by stellar parallax.
E)It's a cluster that has been photographed over many decades, so we know how the stars vary in brightness.

Question 62

This figure shows the Cepheid period- luminosity relation. What is the approximate luminosity of a Cepheid star that varies in brightness on a 10 day cycle?

A)about 1000 times the luminosity of the sun
B)about 30,000 times the luminosity of the sun
C)about 10,000 times the luminosity of the sun
D)about 3000 times the luminosity of the sun

Question 63

How does a lenticular galaxy differ from a normal spiral galaxy?

A)It has no gas or dust.
B)It is flatter in shape.
C)It has an elongated bulge resembling a bar more than a sphere.
D)It has no bulge.
E)It has no spiral arms.

Question 64

Which of the following phenomena are not thought to be results of collisions or other interactions between galaxies?

A)the fact that elliptical galaxies are more common in clusters of galaxies than outside clusters
B)starbursts
C)the fact that spiral galaxies have both disk and halo components
D)the presence of very large, central dominant galaxies in clusters of galaxies

Question 65

What is a quasar?

A)a star- like object that actually represents a bright patch of gas in the Milky Way
B)the name given to the largest objects in the Kuiper Belt
C)a very large galaxy thought to be formed by the merger of several smaller galaxies, resulting in a quick burst of star formation
D)another name for very bright stars of spectral type O
E)the extremely bright center of a distant galaxy, thought to be powered by a supermassive black hole

Question 66

Molly measures a Hubble constant of 20 km/sec/million light- years. Sam measures a Hubble constant of 25 km/sec/million light- years. All other assumptions being the same, which person would estimate a LARGER age to the universe?

A)Sam
B)Molly
C)They both would measure the same age.

Question 67

Most active galactic nuclei are at large distances from us; relatively few nearby galaxies harbor active galactic nuclei. What does this imply?

A)Active galactic nuclei can form only at large distances from the Milky Way.
B)Massive black holes existed only when the universe was young and no longer exist today.
C)Active galactic nuclei tend to become less active as they age.
D)The jets seen in many active galactic nuclei must cause them to move far away from us.

Question 68

What is the most accurate way to determine the distance to a very distant galaxy?

A)main- sequence fitting
B)Hubble's law
C)Cepheid variables
D)Stellar parallax
E)white dwarf supernova

Question 69

What makes white- dwarf supernovae very good standard candles for distance measurements?

A)They are very bright, so they can be used to determine the distances to galaxies billions of light- years away.
B)They should all have approximately the same luminosity.
C)We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately.
D)They occur so frequently that we can use them to measure the distances to virtually all galaxies.
E)both A and B

Question 70

Which of the following is not one of the three major categories of galaxies?

A)spiral galaxies
B)elliptical galaxies
C)irregular galaxies
D)globular galaxies

Question 71

Compared to spiral galaxies, elliptical galaxies are

A)bluer and flattened.
B)redder and rounder.
C)always much smaller.
D)redder and flattened.
E)bluer and rounder.

Question 72

What is the current limit to distances we can measure via parallax, until the results of the new Gaia mission become available?

A)about 100 light years
B)about 1000 light years
C)about 100,000 light years
D)about 10,000 light years

Question 73

Dr. X believes that the Hubble constant is H0 = 20 km/s/Mly while Dr. Y believes it is H0 = 24 km/s/Mly. Which statement below automatically follows?

A)Dr. X believes that the universe is older than Dr. Y believes.
B)Dr. X believes that the Andromeda Galaxy (a member of our Local Group)is moving away from us at a slower speed than Dr. Y believes.
C)Dr. X believes that the universe has a much higher density than Dr. Y believes.
D)Dr. X believes that the universe is expanding, but Dr. Y does not.
E)Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever.

Question 74

Which of the following phenomena is probably not related to the presence of a supermassive black hole?

A)the presence of globular clusters in the halos of galaxies
B)the radio emission from radio galaxies
C)the huge jets seen emerging from the centers of some galaxies
D)quasars

Question 75

Which of the following processes slowed the collapse of protogalactic clouds?

A)the radiating away of thermal energy
B)the formation of the first generation of stars
C)the shock waves from the exploding supernovae of the earliest stars
D)the pull of gravity of the mass of the cloud material
E)the conversion of gravitational potential energy into kinetic and thermal energy as the cloud collapsed

Question 76

Recall that a raisin cake is sometimes used to imagine how an expanding universe behaves. Suppose you are in a uniformly expanding raisin cake, sitting on Raisin A, looking at Raisin B, 2 cm away from you. Raisin B is moving away from you at 1 cm/sec. At the same time, you observe another Raisin C, which is moving away from you at 3 cm/sec. How far away is Raisin C from Raisin A?

A)2/3 cm
B)3/2 cm
C)6 cm
D)3 cm
E)impossible to say

Question 77

Most active galactic nuclei are found at large distances from us, with relatively few nearby. What does this imply?

A)Supermassive black holes existed only when the universe was young, and no longer exist today.
B)Active galactic nuclei can form only at large distances from the Milky Way.
C)The jets seen in many active galactic nuclei must cause them to move far away from us.
D)Active galactic nuclei tend to become less active as they age.

Question 78

Use the graph above showing data for the brightest galaxies in clusters of galaxies to answer the following questions. Which statement describes this graph?

A)The more distant the galaxy, the redder it is, but there are some exceptions.
B)The more distant the galaxy, the bluer it is, but there are some exceptions.
C)There is no trend because there are some exceptions.

Question 79

Approximately how many stars does a dwarf elliptical galaxy have?

A)less than a million
B)1 trillion
C)100 billion
D)less than a billion
E)10 billion

Question 80

How many more stars does a starburst galaxy form, in one year, than the Milky Way?

A)about ten
B)about a thousand
C)about a hundred
D)a few
E)about the same, but it does so for much longer