Deck 23: Galaxies

Question 1

The masses of galaxies are often determined by

A)Determining their star formation rates
B)Counting their stars
C)Measuring their tidal forces on the Milky Way
D)Measuring their rotation curves

Answer 1

Measuring their rotation curves

Question 2

The Milky Way galaxy is

A)Irregular
B)Elliptical
C)Spiral
D)Barred spiral

Answer 2

Barred spiral

Question 3

What evidence do we have that galaxies have extended haloes of dark matter?

A)Orbital speed doesn't fall off in the outer parts of galaxies
B)The outer parts of galaxies are intense infrared sources
C)Light from background galaxies is blocked by the dark matter
D)The orbits of distant globular clusters are distorted by the dark matter

Answer 3

Orbital speed doesn't fall off in the outer parts of galaxies

Question 4

The most massive galaxies in the universe are

A)Elliptical
B)Spiral
C)Barred spiral
D)Irregular

Question 5

Suppose stars at 1000 ly from the center of a galaxy and those at 2000 ly from the center of the galaxy both revolve at the same speed.How would the mass within 2000 ly of the center of the galaxy compare to the mass within 1000 ly of the center of the galaxy?

A)Twice as great
B)Half as great
C)The same
D)1000 times as great

Question 6

A primary difference between spiral and elliptical galaxies is

A)All ellipticals are more massive than spirals
B)Ellipticals have more extensive interstellar media than spirals
C)Star formation has ceased in ellipticals,but not in spirals
D)Spirals have more stars than ellipticals

Question 7

The most numerous galaxies are probably

A)Irregulars
B)Spirals.
C)Ellipticals
D)Barred spirals

Question 8

Which of the following is the best description of an SBc galaxy?

A)A barred spiral galaxy with loose,open arms
B)A spiral galaxy with tightly wound arms
C)A relatively faint quasar
D)An irregular galaxy in the Sculptor cluster

Question 9

Suppose a galaxy has a flat rotation curve.How does the amount of mass within 20 kpc compare to the amount of mass within 10 kpc?

A)Twice as great
B)4 times as great
C)Half as great
D)One-quarter as great

Question 10

One would expect the Hertzsprung-Russell diagram of an elliptical galaxy to resemble that of a(n)

A)Globular star cluster
B)Open star cluster
C)Star formation region
D)Irregular galaxy.

Question 11

A barred spiral with loosely wound arms would be classified

A)SBc
B)Sb
C)BS
D)S0a

Question 12

Which of the following types would be assigned to a normal spiral galaxy with a bright nucleus and tightly wound spiral arms?

A)SBa
B)Sa
C)SBc
D)Sc

Question 13

The Magellanic clouds are

A)Ellipticals
B)Spirals
C)Barred spirals
D)Irregulars

Question 14

Elliptical galaxies are reddish in color because they

A)Shine due to synchrotron radiation
B)Are moving away faster than other galaxies
C)Contain relatively few young,hot stars
D)Are surrounded by intergalactic dust clouds

Question 15

A rotation curve for a galaxy is a plot of

A)Orbital speed versus distance from center
B)Number of rotations versus time
C)Orbital distance versus eccentricity
D)Amount of mass versus distance from center.

Question 16

The Magellanic clouds are

A)Regions of star formation in the Andromeda galaxy
B)Close clusters of galaxies about 10 Mpc away
C)Nearby irregular galaxies gravitationally bound to the Milky Way
D)An optical illusion caused by dust in the interplanetary medium
E)Regions of little gas and dust in the plane of the galaxy

Question 17

A normal spiral with a bright nucleus and tightly wound spiral arms is classified

A)Sba
B)SBc
C)Sa
D)Sc

Question 18

Which type of galaxy contains the least amount of interstellar material?

A)Ellipticals
B)Spirals
C)Barred spirals
D)Irregulars

Question 19

What type of galaxy is the Andromeda galaxy (M31)?

A)Barred spiral
B)Normal spiral
C)Elliptical
D)Irregular

Question 20

A spiral galaxy with a small nucleus and loosely wound spiral arms would be classified

A)Sc
B)Sba
C)S0
D)Sa

Question 21

The expansion of the universe was discovered by

A)Hertzsprung
B)Schmidt
C)Penzias and Wilson
D)Hubble

Question 22

A super massive black hole at the center of the Andromeda Galaxy is estimated to contain between __________ solar masses.

A)100 to 1000
B)1000 to 100,000
C)10 million to 100 million
D)10 billion to 100 billion

Question 23

If a dwarf elliptical galaxy has an absolute magnitude of -15 and could be detected to an apparent magnitude of +20,how far away could such a galaxy be and still be detected?

A)100 kiloparsecs
B)1 megaparsec
C)10 megaparsecs
D)100 megaparsecs

Question 24

A galaxy at a distance of 10 Mpc is moving away from us at a speed of 800 km/s.What would be the recession speed of a galaxy at a distance of 5 Mpc?

A)800 km/s
B)1600 km/s
C)3200 km/s
D)400 km/s

Question 25

What did early spectroscopic measurements show about spiral nebulae?

A)They are swirling gas clouds
B)Most of them have redshifted spectra
C)None of them are rotating
D)Most of them are within our own galaxy

Question 26

Black hole masses at the centers of galaxies can be estimated by ___________ .

A)measuring the absolute brightness of the galaxy.
B)measuring the orbital speeds of stars near the galactic center.
C)observing the overall shape of the galaxy.
D)determining the galactic type.

Question 27

Which of the following would be least useful in determining distances to other galaxies?

A)Parallax
B)Cepheid variables
C)The sizes of HII regions
D)The brightness of a supernova

Question 28

Which of the following was used by some astronomers in the early 1900s to argue that spiral nebulae were nearby objects?

A)Their large parallaxes
B)Measurements taken several years apart that showed rotation
C)Their small Doppler shifts
D)An absence of globular clusters in spiral nebulae

Question 29

Which of the following is the best analogy for Hubble's law of recession of the galaxies?

A)Raisins carried apart by dough in a rising loaf of raisin bread
B)Fragments of an exploding bomb
C)Leaves blown from a tree by the wind
D)An ocean current carrying a sailboat against the wind

Question 30

Hubble's relationship between the distance to a galaxy and its speed of recession is interpreted as evidence for

A)The expansion of the universe
B)Galaxies being outside the Milky Way
C)The evolution of galaxies
D)The Doppler effect

Question 31

According to current ideas on the evolution of galaxies,in the remote past,elliptical galaxies would have been

A)Much more massive than at present
B)Redder and fainter than now
C)The only type of galaxy in the universe
D)Brighter and bluer than at present

Question 32

A galaxy at a distance of 100 Mpc is receding at 6000 km/s.How far away is a galaxy that is receding at 24,000 km/s?

A)400 Mpc
B)600,000 Mpc
C)25 Mpc
D)200 Mpc

Question 33

The black hole mass at the center of the Sombrero Galaxy may be as large as __________ solar masses.

A)one billion
B)one million
C)100 billion
D)100 million

Question 34

A strong argument in favor of the theory that the universe is expanding is the observation of the

A)Ratio of helium to hydrogen of .25
B)Red shift of galaxies
C)Cosmic background radiation
D)Existence of quasars

Question 35

How was Hubble able to determine the distances of nearby galaxies?

A)By measuring the expansion speeds of supernova shells
B)By measuring trigonometric parallaxes
C)By measuring their radial velocities
D)By observing Cepheid variables in them

Question 36

Suppose an astronomer living on a planet in a galaxy of the Perseus cluster (distance = 300 Mpc)looked back at our Milky Way galaxy.If she measured the hydrogen line H alpha (rest wavelength 6500 A),what wavelength would she actually measure? (H = 70 km/s/Mpc)

A)6955 A
B)6500 A
C)5850 A
D)6200 A
E)6600 A

Question 37

A collision of two large spiral galaxies is likely to result in the formation of what type of galaxy?

A)Barred spiral
B)Normal spiral
C)Elliptical
D)None of the above,galaxies pass through each other with little interaction between them.

Question 38

Hubble's law describes the relationship between

A)Red shift and recession speed
B)Distance and parallax
C)Distance and red shift
D)Red shift and composition

Question 39

Physically,the Hubble constant is a measure of the

A)Luminosity of a galaxy
B)Strength of hydrogen lines in galaxies
C)Relation between temperature and age of a galaxy
D)Age of the universe