Deck 12: The Milky Way Galaxy

Question 1

___________ of the Milky Way contains mostly old (population II) stars and globular clusters.

A) The disk component
B) The spherical halo component
C) The hydrogen gas in the disk
D) The spiral arms
E) Sgr A^*

Answer 1

B

Question 2

Good tracers of the spiral arms of our galaxy are all
I) very old.
II) very young.
III) very luminous.
IV) moving with large radial velocities.

A) I & III
B) I & IV
C) II & III
D) II & IV
E) I, III, & IV

Answer 2

C

Question 3

Younger stars have more heavy elements because

A) old stars destroy heavy elements as they age.
B) young stars burn their nuclear fuels faster.
C) the heavy elements were made in previous generations of stars.
D) heavy elements haven't had time to settle to the core of these younger stars.
E) All of the other choices are correct.

Answer 3

C

Question 4

Who first used RR Lyrae variable stars to determine distances in our Milky Way galaxy?

A) Henrietta Leavitt
B) Edwin Hubble
C) John Glenn
D) Carl Sagan
E) Harlow Shapley

Question 5

Pulsating variable stars are useful in determining

A) the mass of a star for which the distance is known.
B) the temperature of a star for which we know the luminosity.
C) the radius of the bulge of our galaxy.
D) the distance to globular clusters.
E) the mass of the Milky Way galaxy.

Question 6

Which of the following is not a characteristic of the stars of the disk component of our galaxy?

A) circular orbits
B) randomly inclined orbits
C) higher metal abundance
D) young stars
E) star-formation regions

Question 7

The center of our galaxy lies in the direction of (but far beyond) the stars in the constellation of

A) Ursa Minor.
B) Ursa Major.
C) Sagittarius.
D) Orion.
E) Monoceros.

Question 8

The first stars to form in our galaxy

A) had circular orbits.
B) had highly elongated elliptical orbits.
C) were population I stars.
D) all had orbits in the same plane.
E) formed the galactic clusters we see today.

Question 9

Population II stars
I) are primarily found in the disk of the galaxy.
II) contain more heavy metals than population I stars.
III) are primarily old low-mass stars.
IV) are located in globular clusters.

A) III & IV
B) I & II
C) II
D) IV
E) I, II, & III

Question 10

CO observations of the galaxy reveal

A) the location of dense neutral hydrogen clouds.
B) the location of population II stars.
C) the location of population I stars.
D) the location of the galactic corona.
E) the location of giant molecular clouds.

Question 11

The galactic halo or corona is believed to contain mostly

A) O and B stars.
B) G, K, and M stars.
C) open clusters.
D) globular clusters.
E) dark matter.

Question 12

Who first determined that the energy/s emitted by (luminosity of) Cepheid variable stars is larger the longer their period of variation is?

A) Henrietta Leavitt
B) Edwin Hubble
C) John Glenn
D) Carl Sagan
E) Harlow Shapley

Question 13

The nuclear bulge of our galaxy

A) contains stars that are primarily population I stars.
B) is primarily composed of gas and dust.
C) contains stars primarily associated with the spherical component of our galaxy.
D) contains stars primarily associated with the disk component of our galaxy.
E) contains stars that are primarily population I stars, is primarily composed of gas and dust, and contains stars primarily associated with the disk component of our galaxy.

Question 14

If the spiral density wave were the only thing producing spiral arms, it would be expected that

A) all spiral arms would be gas and dust free.
B) all galaxies would have only two smooth spiral arms.
C) the Milky Way would show and irregular pattern of short arms .
D) the Milky Way wouldn't have any spiral arms.
E) the halo component of the Milky Way would show spiral arms as well.

Question 15

The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on

A) observations of globular clusters.
B) observations of open clusters.
C) 21-cm radiation from H I regions.
D) the rotation curve of the galaxy.
E) the energy produced by Sagittarius A*.

Question 16

The energy source at the center of our galaxy

A) is not visible at optical wavelengths.
B) produces X-rays.
C) must be less than 10 AU in diameter.
D) is not visible at optical wavelengths, produces X-rays, and must be less than 10 AU in diameter.
E) None of the other choices are correct.

Question 17

___________ in other galaxies should contain luminous O and B stars if they are like the Milky Way.

A) The halos
B) The bulges
C) The spiral arms
D) The globular clusters
E) The coronas

Question 18

Nucleosynthesis

A) is the process by which energy is produced at the center of the galaxy.
B) is the process by which hydrogen and helium are converted into heavier elements.
C) describes the structure of a globular cluster.
D) describes how the magnetic field of the galaxy traps cosmic rays.
E) describes the method by which neutral hydrogen produces 21-cm radiation.

Question 19

Our galaxy is suspected to be surrounded by a galactic halo or corona because the disk of the galaxy

A) rotates faster than expected in its outer region.
B) rotates more slowly than expected in its outer region.
C) is only visible during a total eclipse of our Sun.
D) is surrounded above, below, and well beyond by the brightly glowing corona.

Question 20

The chemical abundance of population I stars

A) indicates that they were formed before the population II stars.
B) indicates that the material they formed from had been enriched with material from supernovae.
C) indicates that they contain very few heavy metals compared to halo stars.
D) depends on the temperature of the star.
E) depends on the mass of the star.

Question 21

This is a "thought" question. Why are few galaxies outside our own galaxy seen by our eyes in the circle around the sky where the Milky Way is located? This is because

A) there aren't any galaxies in those directions.
B) dust in the Milky Way blots out our view of galaxies in those directions.
C) the missing mass is in those directions.
D) a massive explosion has blown galaxies away from those directions.

Question 22

In the edge-on sketch of a spiral galaxy, pick the letter corresponding most nearly to the location of globular clusters.

A) A
B) B
C) C
D) D

Question 23

The Herschels' grindstone model of the Milky Way star system was too small because

A) they did not count the brightest stars.
B) they did not study the southern sky.
C) they did not have large enough telescopes.
D) they only observed stars in the disk of the galaxy and not the halo.
E) they did not know about interstellar dust clouds.

Question 24

What behavior do galactic rotation curves exhibit to suggest the existence of dark matter in an extended halo?

A) Small velocities are seen at large distances from the galactic center.
B) Small velocities are seen at distances close to the galactic center.
C) Large velocities are seen at large distances from the galactic center.
D) Large velocities are seen at distances close to the galactic center.

Question 25

Sgr A* is believed to be the center of the Milky Way galaxy because
I) it lies in the general direction of the center of the galaxy based on observations of globular clusters in the plane of the Milky Way.
II) long-wavelength dust-penetrating images show it to be a region crowded with stars.
III) orbits of stars around it indicate a mass several million times that of the Sun within a volume a few light hours in size.
IV) radio observations show it is a concentrated source at the center of swirling clouds of gas.

A) I & II only
B) II & III only
C) I & IV only
D) II & IV only
E) All of I, II, III, & IV

Question 26

Radio maps of the spiral arms of our galaxy

A) reveal that our galaxy is a grand design spiral.
B) map the location of hot O and B stars by the radio radiation they emit.
C) reveal that the spiral arms are winding up and growing closer together.
D) reveal that the Sun is currently located in the center of a spiral arm.
E) map the location of dense neutral hydrogen clouds.

Question 27

The energy source at the center of our galaxy is called

A) Cygnus X-1.
B) the Orion arm.
C) the Sun.
D) Sagittarius A*.

Question 28

How did Harlow Shapley determine where the center of the galaxy lies?

A) He plotted the distribution of open clusters.
B) He plotted the distribution of globular clusters.
C) He made star counts in every direction of the galactic disk.
D) He measured the amount of dust obscuration in every direction of the galactic disk.

Question 29

The traditional "top-down" hypothesis states that the galaxy formed

A) from a large spherical cloud of gas that was rotating very slowly.
B) from a large cloud of material that broke off a larger galaxy.
C) from material that had been ejected in the violent explosion of a dying galaxy.
D) as a result of mergers between several smaller groups of gas, dust, and stars.
E) as two massive galaxies collided.

Question 30

The center of our galaxy lies in the direction of the constellation of

A) Ursa Minor.
B) Ursa Major.
C) Sagittarius.
D) Orion.
E) Monoceros.

Question 31

How is the age of the galaxy determined?

A) measuring the metallicity of Population II stars
B) finding the turnoff point in the H-R diagram of globular clusters
C) from the motion of stars in the galactic halo
D) counting the number of open clusters in the spiral arms

Question 32

Which of the following can't be associated with the spiral arms of a galaxy?

A) dust and gas
B) metal-poor stars
C) young, massive stars
D) star formation

Question 33

Figure 12-1 Refer to Figure 12-1. A Type II Cepheid has been located in a distant globular cluster with a period of 10 days. What is the star's absolute magnitude?

A) − 1
B) 0
C) − 4
D) − 6
E) The absolute magnitude of a Cepheid variable cannot be determined unless its distance is known.

Question 34

The traditional "top-down" hypothesis of the formation of our galaxy cannot explain

A) why not all globular clusters are the same age.
B) why the youngest globular clusters are in the outer halo.
C) why the oldest stars are metal poor but not completely metal free.
D) streams and rings of scattered stars in the halo.
E) All of the other choices are correct.

Question 35

The disk of our galaxy consists of

A) the nine known planets.
B) only stars.
C) stars, dust, and gas.
D) quasars.
E) only black holes.

Question 36

The orbits of population I stars
I) are confined to disk of the galaxy.
II) are very elliptical.
III) are nearly circular.
IV) are randomly inclined to the disk of the galaxy.

A) I
B) IV
C) I & IV
D) II & IV
E) I & III

Question 37

Figure 12-1 Refer to Figure 12-1. A Type I Cepheid has been located in an open cluster. The period of the Cepheid variable is 30 days and the variables apparent visual magnitude, m , is 10. First, use 12-1 to estimate the absolute visual magnitude, M . Calculate the distance to this open cluster? Hint: d _pc = 10^{( m - M + 5)/5}

A) 100 pc
B) 10,000 pc
C) 20 pc
D) 300 pc
E) 2500 pc

Question 38

The mass of the black hole at the center of our galaxy can be estimated using the ____ of a star orbiting it.

A) semi-major axis
B) orbital period
C) semi-major axis and orbital period
D) neither semi-major axis nor orbital period

Question 39

How did Harlow Shapley use the period-luminosity relationship of RR Lyrae variables to determine the size of the Milky Way galaxy?

A) He determined the proper motion of globular clusters in the outer disk of the galaxy.
B) He found the distances to individual variables free floating in the halo.
C) He found the distances to open clusters found throughout the disk of the galaxy.
D) He found the distances to globular clusters distributed about the center of the galaxy.

Question 40

The first scientific attempt to map the Milky Way galaxy

A) showed that the Sun was located in the center of the system of planets making up our galaxy.
B) showed that our galaxy is a round ball on which we live.
C) showed that our galaxy has 9 stars.
D) used globular clusters to determine the location of the center of the Earth.
E) was completed by William and Caroline Herschel.

Question 41

The spherical component is the __________.

A) halo
B) bulge
C) halo and bulge
D) dark matter

Question 42

More massive stars are _________ luminous and __________ than less massive stars, thus they pulsate _____________.

A) less, smaller, faster
B) more, larger, slower
C) more, larger, slower
D) less, smaller, faster

Question 43

Where are the Large Magellanic Cloud and Small Magellanic Cloud located?

A) in the spiral arms
B) in the disk
C) in the bulge
D) None of the other choices are correct.

Question 44

The above light curve shows a period that indicates ________________________.

A) the star gets dimmer quickly and brighter gradually
B) the star gets brighter quickly and dimmer gradually
C) the binary star system has an elliptical orbit
D) the system remains at constant absolute magnitude

Question 45

The galaxy shown above is ___________.

A) a grand design
B) a flocculent
C) in between a grand design and a flocculent
D) the Milky Way galaxy

Question 46

The blue color in this visual wavelength image indicates

A) globular clusters.
B) halo stars.
C) young stars.
D) cool stars.

Question 47

What is the orientation of the galaxy shown above relative to us on Earth?

A) edge-on
B) face-on
C) nearly edge-on
D) None of the other choices are correct.

Question 48

The relative abundance of chemical elements are shown by atomic mass number. Of those shown, which is the most abundant?

A) hydrogen
B) helium
C) carbon
D) iron

Question 49

What color in the above image best represents the bulge?

A) pink
B) blue
C) black
D) milky white

Question 50

In the above graph, what does 5.36634 indicate according to your text?

A) orbital period
B) rotation period
C) period of the star changing size
D) period of the star changing brightness

Question 51

The relative abundance of chemical elements are shown by atomic mass number. Which is/are the metal(s)?

A) helium
B) carbon, nitrogen, oxygen
C) hydrogen, helium
D) carbon, nitrogen, oxygen, iron

Question 52

Compared to stars within the disk, halo stars

A) orbit at random inclinations to the galactic plane
B) orbit at different speeds
C) orbit with paths crossing
D) All of the other choices are correct.

Question 53

You observe a variable star and find its period to be about 6 days and its M _V to be -3.4. Which object best describes the system or type of system you are observing using the above graph?

A) RR Lyrae
B) Type II Cepheids
C) Type I Cepheids
D) Delta Cephei

Question 54

Which of the above shown variable types is brightest?

A) RR Lyrae
B) Type II
C) Type I
D) all are equally as bright

Question 55

What kind of galaxy is shown above?

A) flocculent
B) grand design
C) wooly
D) None of the other choices are correct.

Question 56

What is the orientation of the galaxy shown above relative to Earth?

A) face-on
B) edge-on
C) not quite edge-on
D) not quite face-on

Question 57

The pink color in the above visual image is from __________.

A) a reflection nebula
B) a dark nebula
C) an emission nebula
D) pink stars

Question 58

In which direction is the above spiral galaxy rotating and which color best represents where the gas is being compressed by the spiral density wave?

A) clockwise, blue
B) counter-clockwise, pink
C) clockwise, pink
D) counter-clockwise, blue

Question 59

Which pulsate faster?

A) lower mass, smaller stars
B) higher mass, larger stars
C) dimmer, smaller stars
D) brighter, smaller stars

Question 60

Which mass star experiences more pulsations than the others shown at the time the systems were plotted in the above H-R diagram?

A) 9-solar-mass star
B) 5-solar-mass star
C) 3-solar-mass star
D) RR Lyrae

Question 61

Any element heavier than helium is collectively referred to as a _______________.

Question 62

RR Lyrae stars are in the constellation ___________.

Question 63

The ____________________ hypothesis suggests that the Milky Way galaxy formed from a single cloud that flattened into a disk.

Question 64

Which stellar population has highly elliptical orbits?

A) Pop I extreme
B) Pop I intermediate
C) Pop II intermediate
D) Pop II extreme

Question 65

_______________ is the rate at which a star moves across the sky.

Question 66

As viewed from above or face-on, a ____________ spiral galaxy has many branches and spurs, making the arms less discernible.

Question 67

The center of the Milky Way galaxy must be less than 1 AU in diameter and contain at least 4 million solar masses. Therefore, the center of the Milky Way galaxy must be a ____________________,

Question 68

O and B stars are examples of ________________ that are used to outline the arms in a galaxy like the Milky Way galaxy.

Question 69

____________________ are groups of 100,000 to 1,000,000 population II stars firmly bound by gravity.

Question 70

Henrietta Leavitt discovered the period-luminosity relationship for ____________________.

Question 71

The _________________ hypothesis includes mergers with smaller galaxies and infalling gas to the standard formation of the Milky Way galaxy.

Question 72

The production of elements heavier than helium by fusion in stars and during supernova explosions is called ______________________.

Question 73

Globular clusters are primarily found in the ____________________ component of the galaxy.

Question 74

The ____________________ of the galaxy contains population I stars, open clusters, and gas clouds.

Question 75

Shapley found the distance to the center of the galaxy by studying the distance to open clusters.

Question 76

The center of our galaxy is located in the direction of the constellation of Orion.

Question 77

In the diagram below, the approximate absolute magnitude of a Type II Cepheid with a period of 30 days is ____________________.

Question 78

Regions of compression that move at their own speed in the disk and are outlined by the spiral arms are _____________.

Question 79

The center of our galaxy is believed to be occupied by the radio source known as ____________________.

Question 80

The rotation curve of the galaxy provides evidence for the existence of the ____________________ which extends beyond the halo of the galaxy.