Deck 16: Galaxies

Question 1

Gravitational lensing can be used to detect the presence of dark matter.

Answer 1

True

Question 2

Galaxies contain 10 times as much dark matter as visible matter.

Answer 2

True

Question 3

When spiral nebulae were first discovered, astronomers quickly identified them as distant groupings of stars.

Answer 3

False

Question 4

Spiral and irregular galaxies have active star formation.

Question 5

A standard candle is an object with a known luminosity.

Question 6

Gentle gravitational tidal forces appear to be necessary to create spiral arms.

Question 7

The identification of "spiral nebulae" as large groupings of stars outside of our own galaxy was proven by ____.

A) photographic plates made by Edwin Hubble showing stars and Cepheid variables
B) the results of the Shapley-Curtis debate
C) Immanual Kant's "island universe" theory
D) William Parsons' observation and description of their spiral structure
E) Harlow Shapley's observations of their radio spectrum

Question 8

In which of the following types of galaxies would you expect to find active star formation?

A) elliptical galaxies only
B) elliptical and spiral galaxies
C) spiral galaxies only
D) elliptical and irregular galaxies
E) spiral and irregular galaxies

Question 9

The Milky Way galaxy has collided with several other large galaxies in its lifetime.

Question 10

"Starburst" events are a common outcome of galactic collisions.

Question 11

Elliptical galaxies contain a mix of old and young stars.

Question 12

All elliptical galaxies are more massive than the largest spiral galaxies.

Question 13

Which types of galaxies would contain very little gas and dust?

A) elliptical galaxies only
B) elliptical and spiral galaxies
C) spiral galaxies only
D) elliptical and irregular galaxies
E) spiral and irregular galaxies

Question 14

Globular clusters can be used to measure the distance of nearby galaxies.

Question 15

Which types of galaxies lack an ordered structure of stellar orbits?

A) elliptical galaxies only
B) spiral galaxies only
C) irregular galaxies only
D) elliptical and irregular galaxies
E) spiral and irregular galaxies

Question 16

The farthest galaxies that astronomers have seen are all elliptical galaxies.

Question 17

Hubble's Law is only effective in measuring the distance to nearby galaxies.

Question 18

NASA's Hubble Deep Field images and GOODS program observations have shown that ____.

A) there are large patchy regions of the sky covered with galaxies separated by empty areas
B) the entire sky is thickly covered with galaxies
C) galaxies can be found in all directions, but are relatively rare
D) galaxies are densely concentrated in a disk structure, which contains the Milky Way
E) galaxies are concentrated in two opposite directions on the sky, with very few in between

Question 19

Giant spirals are the largest galaxies in the Universe.

Question 20

The diameter and luminosity of a galaxy do not determine its type.

Question 21

The ____ depend(s) on the assumption that the mass of a galaxy or galactic cluster is large enough to keep moving matter bound to the main structure.

A) rotation curve method
B) velocity dispersion and cluster methods
C) Shapley-Curtis and Hubble methods
D) recessional velocity method
E) tangential velocity method

Question 22

A supermassive black hole in the center of a galaxy typically represents ____ of the galaxy's total mass.

A) a tiny fraction of a percent
B) about a percent
C) 1-5%
D) 10%
E) 50%

Question 23

The mass of visible matter in a galaxy can be estimated by measuring its luminosity. When this is compared with the measured mass of the galaxy, astronomers find that ____.

A) the measured mass is about ten times the estimated mass, due to the effects of the central black hole
B) the measured mass is approximately equal to the estimated mass
C) there is no clear relationship between the estimated and measured mass
D) the measured mass is about ten times the estimated mass, due to the effects of dark matter
E) the estimated mass is about ten times the measured mass, due to the effects of dark matter

Question 24

In order to calculate the size and luminosity of a galaxy, you must first determine its ____.

A) age
B) mass
C) shape
D) metallicity
E) distance

Question 25

The range of diameters and luminosities displayed by elliptical galaxies is ____.

A) similar to the range of spirals, and smaller than spiral galaxies on average
B) similar to the range of spirals, and about the same as spiral galaxies on average
C) similar to the range of spirals, and larger than spiral galaxies on average
D) wider than the range for spirals, extending to much larger sizes than spiral galaxies
E) wider than the range for spirals, extending to much smaller sizes than spiral galaxies

Question 26

In general, ____.

A) spiral galaxies are the most common galaxies, and are make up most of the cataloged galaxies
B) elliptical galaxies are the most common galaxies, and are make up most of the cataloged galaxies
C) most cataloged galaxies are spiral, but dwarf galaxies are the most common
D) most cataloged galaxies are elliptical, but spiral galaxies are the most common
E) most cataloged galaxies are spiral, but elliptical galaxies are the most common.

Question 27

A key piece of evidence that leads astronomers to conclude that most galaxies include a supermassive black hole in the center is that ____.

A) high-speed disks of gas are observed in the central parsecs of other galaxies
B) streamers of gas from stars that have been torn apart are detected in most galactic centers
C) stars near the center of other galaxies are orbiting more rapidly than expected
D) the mass of all galaxies is much more than expected based on the visible material in the galaxy
E) the disks of all spiral galaxies rotate more quickly than Kepler's laws predict

Question 28

The rotation curve of a galaxy is important in determining the galaxy's ____.

A) mass
B) age
C) luminosity
D) type
E) diameter

Question 29

Cepheids and globular clusters are limited in their ability to measure the distance to galaxies because they ____.

A) are too rare
B) are not bright enough to detect at large distances
C) behave differently in other galaxies than they do in our own
D) do not appear in dwarf galaxies
E) are only found in elliptical galaxies

Question 30

The mass of a galaxy's central black hole is related to the mass of the galactic bulge. This implies that ____.

A) central black holes formed when the galaxy bulges formed
B) central black holes have grown during the galaxy's lifetime as the galactic bulge has grown
C) galactic bulges shrink over time as mass is consumed by the central black hole
D) central black holes cause the formation of galactic bulges
E) black holes are only present in spiral galaxies

Question 31

Because t he Hubble constant has a value of 70 km/s/Mpc, a galaxy 100 Mpc away would have a recession velocity of ____.

A) 0.7 km/s
B) 1.43 km/s
C) 30 km/s
D) 170 km/s
E) 7,000 km/s

Question 32

Dark matter is detectable in the coronae of ____.

A) elliptical galaxies only
B) spiral galaxies only
C) irregular galaxies only
D) spiral and elliptical galaxies only
E) all galaxies

Question 33

Globular clusters can be used to estimate the distance to galaxies by measuring the clusters' ____.

A) angular diameter
B) mass
C) orbital speed
D) age
E) recession velocity

Question 34

Compared to other spiral galaxies, the Milky Way is ____.

A) comparable to the smallest and dimmest spirals known
B) smaller and dimmer than most spirals
C) very average in size and luminosity
D) larger and brighter than most spirals
E) comparable to the largest and brightest spirals known

Question 35

Cepheid variables are useful in measuring the distance to ____.

A) globular clusters and dwarf galaxies around the Milky way, but nothing farther
B) globular clusters and the Andromeda Galaxy, but not more distant objects
C) galaxies that are within 30 megaparsecs, a relatively short distance
D) galaxies that are moderately far away, up to about 500 megaparsecs
E) galaxies and galactic clusters within a gigaparsec of the Milky Way

Question 36

An astronomer would find a type Ia supernova in a distant galaxy useful as a(n) ____.

A) spiral tracer
B) gravitational lens
C) age calibration
D) rotation curve
E) standard candle

Question 37

The structure of most galaxies is most apparent using near-infrared images that show the locations of ____.

A) dense molecular clouds
B) spiral tracers
C) atomic hydrogen clouds
D) cool, low-luminosity stars
E) hot, high-luminosity stars

Question 38

Edwin Hubble and Milton Humason discovered that there was a linear relationship between a galaxy's ____.

A) rotation curve and distance
B) mass and luminosity
C) age and distance
D) apparent recession velocity and distance
E) mass and recession velocity

Question 39

The Hubble law is one of the most important relations in modern astronomy because it ____.

A) allows astronomers to measure the distance to very distant galaxies using only their spectrum
B) explains the difference in the types of galaxies seen in different directions
C) relates the rotation curve of a galaxy to the amount of dark matter it contains
D) connects the mass of a spiral galaxy's bulge to the size of its central black hole
E) determines the mass of a cluster using the rotation period of the galaxies it contains

Question 40

Because the Hubble constant equals 70 km/s/Mpc, a galaxy with a recession velocity of 4,900 km/s would be a distance of ____ Mpc from Earth.

A) 0.014
B) 70
C) 4930
D) 4970
E) 343,000

Question 41

Hot, low-density gas can be detected in galactic clusters through X-ray emission. The gas is important in understanding dark matter because ____.

A) dark matter is responsible for heating the gas
B) dark matter must make the cluster massive enough to hold on to the hot gas
C) the gas may be the source of dark matter
D) the gas is clumped in empty places between galaxies where there is more dark matter
E) the gas is produced by dark matter

Question 42

Gravitational lensing is caused by ____.

A) refraction of light through hot intracluster gas
B) stimulated emission of light passing through dark matter
C) acceleration of photons by supermassive black holes
D) scattering of photons off of thin intergalactic dust
E) bending of light rays due to the curvature of space-time around a mass

Question 43

Spiral structures and steady star formation depend on ____.

A) gentle gravitational interactions with other galaxies
B) galactic cannibalism
C) major collisions with other galaxies
D) hot intergalactic gas flow
E) supermassive central black holes

Question 44

Galactic collisions ____.

A) are very rare, since few galaxies are in clusters
B) will cause stars in each galaxy to collide and trigger supernova events
C) often trigger bursts of star formation
D) only happen in poor clusters
E) usually break large galaxy into several small ones

Question 45

_______________ are objects of known luminosity used for finding distances.

Question 46

The Milky Way and other spiral galaxies ____.

A) must have formed recently, because they contain young stars
B) formed spiral arms as the result of major collisions with other galaxies
C) created their disks through the process of galactic cannibalism
D) must be very old because they contain so much gas and dust
E) cannot maintain their disk structure if they suffer a major collision

Question 47

Spiral galaxies are mostly found ____.

A) in poor clusters where their disk structure will not be disrupted
B) isolated in space with only small dwarf galaxies nearby
C) in the center of rich clusters where tidal forces can support their arm structure
D) in clusters with hot intergalactic gas helping support star formation
E) orbiting giant elliptical galaxies in a galactic binary system

Question 48

Because the Hubble constant has a value of 70 km/s/Mpc, a galaxy 50 Mpc away would have a recession velocity of _______________ km/s. (Round your answer to the nearest 1 km/s).

Question 49

The velocity dispersion method can be used to find the _______________ of a galaxy.

Question 50

At the longest look-back times, we see ____.

A) redshifted irregular galaxies
B) redshifted dwarf elliptical galaxies
C) redshifted dwarf spiral galaxies
D) blueshifted dwarf spiral galaxies
E) blueshifted dwarf elliptical galaxies

Question 51

Galactic _______________ describes the process of a large galaxy absorbing a smaller one.

Question 52

The mass of a galaxy can be determined from its _______________ curve.

Question 53

A galaxy with randomly oriented elongated star orbits and little gas and dust would be a(n)  _______________ galaxy.

Question 54

Rich galactic clusters ____.

A) are rare, because galaxies are usually isolated in space
B) contain gas that is rich in metals
C) are composed of mostly elliptical galaxies
D) are very spread out, without a defined center
E) contain a wide variety of galaxy types and sizes

Question 55

The mass of a galaxy's central black hole is proportional to the mass of its _______________.

Question 56

S0 galaxies have spiral arms, but little to no gas and dust. This is believed to happen because ____.

A) their gas has been cannibalized by other galaxies
B) they have had bursts of star formation during major collision the gas and dust formed new stars
C) starburst events have used up all of the gas and dust in the disk
D) gas and dust have been stripped from the galaxies as they pass through hot, intergalactic gas
E) tidal interactions have forced the gas into the central bulge

Question 57

One of the rare galaxies that is isolated in space is likely to be a(n) ____.

A) starburst galaxy
B) ultra luminous infrared galaxy
C) dwarf galaxy
D) antenna galaxy
E) spiral galaxy

Question 58

Because the Hubble constant has a value of 70 km/s/Mpc, a galaxy with a recession velocity of 21,000 km/s must be _______________ Mpc from Earth. (Express your answer as a whole number of Mpc)

Question 59

_______________ galaxies have star formation, but no clear shape.

Question 60

The _______________ time is the amount of time it took light to travel from a celestial object to Earth.

Question 61

How are standard candles used to measure distance?

Question 62

Why are methods to determine the distances to galaxies termed the "distance ladder"? Explain the term with examples.

Question 63

All of the farthest detectable galaxies are _______________ galaxies.

Question 64

Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them as distant clouds of billions of stars.

Question 65

Is dark matter important in other galaxies and galactic clusters?

Question 66

A galaxy that has created a large number of young stars all at once is a(n) _______________ galaxy.

Question 67

Briefly describe the characteristics of an elliptical galaxy.

Question 68

How does the Milky Way compare to other spiral galaxies in size?

Question 69

What is galactic cannibalism?

Question 70

A galaxy that has gone through many collisions and mergers must be a(n) _______________ galaxy.

Question 71

How have elliptical and spiral galaxies developed differently through interactions with other galaxies?

Question 72

Discuss two ways of detecting dark matter in distant galaxies and clusters.

Question 73

Gentle tidal interactions are probably necessary to support the formation of _______________ in a galaxy.

Question 74

Gravitational _______________ can be used to detect dark matter.

Question 75

What direct evidence is there for galactic collisions? Discuss examples of directly observable phenomena linked to collisions.