Deck 13: The Milky Way Galaxy

Question 1

Motions of objects near our Galaxy's core suggest the central black hole is about 3.7 billion solar masses.

Answer 1

False

Question 2

In our vicinity, the Galactic disk is about 100 times wider than it is thick.

Answer 2

True

Question 3

Shapley found the Sun is located about half way out the disc from the center of the disk of the Galaxy.

Answer 3

True

Question 4

Stars in the Galactic disk came billions of years before stars in the Galactic halo.

Question 5

From Earth, the center of the Milky Way lies in the direction of the constellation Cygnus.

Question 6

Spiral arms are regions of star formation, which accounts for their blue color.

Question 7

The core of the Milky Way, Sagittarius A, is a strong radio source in the sky.

Question 8

In structure, our Milky Way is most similar to

A) the Large Magellanic Cloud.
B) an upscale version of a globular cluster.
C) M-31, the Andromeda Galaxy.
D) the Orion nebula.
E) none of these.

Question 9

The infall of material in the Galactic halo to the Galactic disk stopped shortly after the formation of globular clusters.

Question 10

The rotation curve for our Galaxy shows stars beyond the Sun moving slower than expected.

Question 11

Our Milky Way Galaxy is now known to be quite similar to the nearby Andromeda Galaxy, M-31.

Question 12

The part of the Milky Way we are most familiar with is the

A) Corona.
B) Galactic Disk.
C) Galactic halo.
D) Galactic Bulge.
E) Galactic center.

Question 13

Most astronomers believe that the stars in the Galactic halo formed in dwarf galaxies or during the merger of these dwarf galaxies.

Question 14

The Milky Way we see in the sky is simply our edge-on view of our home Galaxy.

Question 15

It is harder to map the structure of the Milky Way as a whole in visible light than with any other form of electromagnetic radiation.

Question 16

Shapley found that globular clusters are only found in the Galactic bulge.

Question 17

Henrietta Leavitt first showed the relationship between the mass and luminosity of Cepheids and their period of pulsation; the brighter, the longer this period.

Question 18

The majority of the mass of the Milky Way lies farther out than the Sun's orbit.

Question 19

The Earth lies close to the center of the Galaxy.

Question 20

A pulsating variable star with a period of 10 days would be a Cepheid.

Question 21

For what type of object is the period-luminosity relation used for determining distances?

A) RR Lyrae variables
B) T Tauri variables
C) Cepheids
D) Cataclysmic variables
E) Planetary nebulae

Question 22

The "aspect ratio" of thickness to width of the Galactic disk is about

A) 1:2.
B) 1:5.
C) 1:10.
D) 1:100.
E) 1:1,000.

Question 23

The Galactic Year is the time for our solar system to orbit the Galaxy; it is about

A) 15 million years.
B) 225 million years.
C) 4.5 billion years.
D) 9.6 billion years.
E) 13.5 billion years.

Question 24

In the halo, we do NOT find

A) tidal streams.
B) globular clusters.
C) small satellite galaxies.
D) spiral arms.
E) old white dwarfs.

Question 25

From the Sun, the distance to the Galactic center is about

A) 8 pc.
B) 8,000 pc.
C) 100,000 pc.
D) 225 million pc.
E) 100 billion pc.

Question 26

The period-luminosity relation for Cepheid variables was discovered in 1908 by

A) William Herschel.
B) Henrietta Leavitt.
C) Harlow Shapley.
D) Heber Curtiss.
E) Edwin Hubble.

Question 27

It was the distribution of ________ that showed Harlow Shapley we were nowhere near the center of the Milky Way early in the 20th century.

A) planetary nebulae
B) emission nebulae
C) open clusters
D) globular clusters
E) supernova remnants

Question 28

Which is the correct description of the Sun's location within the Milky Way?

A) At the outer edge of the Galactic bulge but in the plane of the disc
B) In the disc but at its outer edge
C) As Herschel found, very close to the Galactic center
D) Above the disc and about one-third of the Galactic radius from the center
E) In the disc and about one-half a Galactic radius from the center

Question 29

Galactic disks appear blue because

A) they contain no G, K, or M dwarfs.
B) they contain only blue reflection nebulae.
C) dust obscures the longer, red, wavelengths.
D) O and B blue giants are much brighter than G, K, or M dwarfs.
E) dark matter gravitationally shifts all wavelengths towards the blue.

Question 30

From Earth, the view of the Milky Way is a thin band of stars across the night sky. The part of the Milky Way galaxy that is described here is the

A) bulge.
B) spiral arm.
C) disk.
D) halo.
E) globular cluster.

Question 31

The orbits of halo and bulge stars have been compared to

A) planets around the Sun.
B) satellites around planets.
C) comets around the Sun.
D) binary stars.
E) the accretion disc around a black hole.

Question 32

Detailed measurements of the disk and central bulge region of our Galaxy suggest our Milky Way is a

A) dwarf galaxy.
B) spiral galaxy.
C) very flat elliptical galaxy.
D) very dusty irregular galaxy.
E) quasar.

Question 33

Star formation ceased first in the

A) nucleus.
B) spiral arms.
C) bulge.
D) halo.
E) Galactic disk.

Question 34

Most of the new star formation in the Galaxy is found in the

A) halo.
B) spiral arms.
C) bulge.
D) Galactic center.
E) globular clusters.

Question 35

Which is the correct description for the Sun's location in the Galaxy?

A) At the outer edge of the bulge, but along the Galactic equator
B) About 30,000 ly out in the halo
C) At the very outer edge of the disk, but in the Galactic plane
D) In the disk near the Galactic center
E) In the disk, and about half way out from the center

Question 36

The period-luminosity relation is critical in finding distances with

A) RR Lyrae stars.
B) trigonometric parallaxes.
C) spectroscopic parallaxes.
D) Cepheid variables.
E) pulsars.

Question 37

The location of the Galactic center was first found by Harlow Shapley with

A) radio emissions from Sagittarius A.
B) Cepheids of population I in the spiral arms.
C) RR Lyrae variables in the globular clusters.
D) planetary nebulae in the open clusters.
E) infrared observations of the heat from its accretion disk around the black hole.

Question 38

Matter belonging to the Galaxy can be traced out to ________ from the center.

A) 5 kpc
B) 8 kpc
C) 15 kpc
D) 50 kpc
E) 200 kpc

Question 39

Harlow Shapley found the Milky Way was

A) centered on the Earth.
B) much smaller than previously thought.
C) rapidly expanding.
D) much larger than previously thought.
E) uniformly spherical in shape.

Question 40

Which of these is NOT typical of the Galaxy's spiral arms?

A) Hot, young blue stars
B) Emission nebulae like M42
C) O and B stars
D) Open clusters
E) Old giant stars like orange Arcturus

Question 41

Spiral arms are thought to be sites of ________, based on the observations newly formed stars and interstellar dust lanes in and around these features.

Question 42

Using an orbit size of 8 kpc, and a period of 225 million years, the mass of our Galaxy is found to be closest to

A) 10⁶ solar masses.
B) 10⁸ solar masses.
C) 10¹⁰ solar masses.
D) 10¹¹ solar masses.
E) 10¹² solar masses.

Question 43

Which of the following is most like the rotation of stars in the disk of the Milky Way?

A) A DVD in a player
B) The planets in our solar system
C) Cars moving at a constant speed on a circular race track
D) The hands of an analog clock
E) The tire of a car moving

Question 44

Most of the mass of the Milky Way seems to exist in the form of

A) young stars in the disk.
B) old stars in the Galactic halo.
C) hydrogen gas in the disk and spiral arms.
D) dark matter out in the Galactic halo.
E) the black hole in the Galactic center.

Question 45

The spiral structure of the Milky Way is best revealed by ________ cm radio observations of hydrogen atoms.

Question 46

What use are 21 cm radio waves to Galactic astronomers?

A) They cut through the dusty cocoons to let us watch star birth.
B) We can reflect them off the core of the Galaxy.
C) Their Doppler shifts let us map the motions and locations of gas in the spiral arms.
D) They bounce off stars like our Sun to let us precisely measure their distances.
E) They pick up the cool, dark matter much better than can optical telescopes.

Question 47

The major problem faced by optical astronomers in trying to deduce the structure of the Milky Way Galaxy is that we can see only a small part of it because of the ________.

Question 48

Our solar system is in the Galactic ________ of the Milky Way Galaxy.

Question 49

The leading explanation for the existence of spiral arms is

A) shock waves from cyclic supernovae explosions.
B) shock wave from the quasar-like eruption of the Galactic core.
C) passages of spiral density waves through the interstellar medium.
D) passages of massive globular clusters through the Galactic plane.
E) tidal streams of small galaxies being torn up by our monster Galaxy.

Question 50

Between us and the Galactic center, the Milky Way has a mass of

A) several hundred thousand suns.
B) one to two million suns.
C) 250 million suns.
D) 100 billion suns.
E) over a trillion suns.

Question 51

In the solar neighborhood we can map the position of spiral arms by observation of objects that are determined to be relatively ________ in age.

Question 52

Density waves may explain

A) the lack of blue stars in the halo.
B) the random orbits of halo stars.
C) the density of red stars in the bulge.
D) the spiral arm structure of the Galaxy.
E) the large number of open clusters in the halo.

Question 53

Which sequence of formation by age is correct, oldest to youngest?

A) Dark nebulae, planetary nebulae, emission nebulae
B) Spiral arms, bulge, halo
C) Halo, spiral arms, globular clusters
D) Globular clusters, emission nebulae, open clusters

Question 54

In the formation of our Galaxy, the ________ formed first.

A) Galactic disk
B) Galactic center
C) globular clusters
D) planetary nebulae
E) spiral arms

Question 55

In age, Galactic disk stars are typically much ________ than those of the Galactic halo.

Question 56

What observations suggest the mass of the Galaxy goes much farther out than its visible disc?

A) 21 cm maps of the spiral arms
B) The rotation curve of the outermost portions of the disc
C) The orbits of the open clusters in the disc
D) Infrared observations of distant brown dwarfs
E) X-ray images of other galaxies' discs from Chandra

Question 57

What two observations allow us to calculate the Galaxy's mass?

A) The Sun's mass and velocity in orbit of the Galactic center
B) The Sun's age and period of the Galactic Year
C) The Sun's orbital velocity and its distance from the Galactic center
D) The Sun's mass and its age
E) The Sun's composition and luminosity

Question 58

Which method relies on the mass of a dark object revealing its presence?

A) Asteroidal occultations
B) Ring occultations
C) Stellar eclipses
D) Temporary brightening of a distant star by a gravity lens
E) Pulsars slowing down irregularly

Question 59

The radio source ________ is located in a place consistent with the center of our Galaxy.

A) Cygnus X-1
B) 3C 273
C) 47 Tucanae
D) M-8, the Lagoon Nebula
E) Sgr A*

Question 60

Henrietta Leavitt's period-luminosity relation for ________ indicates that longer periods mean more luminosity.

Question 61

What features of the telescopic view of the Andromeda Galaxy, M-31, are also visible to the naked eye for our similar Galaxy?

Question 62

What is the evidence to support the existence of a black hole at the center of the Milky Way?

Question 63

What do the orbits of halo and disk stars tell us about the formation of the Milky Way?

Question 64

Why were globular clusters so vital to Harlow Shapley's success?

Question 65

Arcturus shows a large proper motion, almost perpendicular to the Galactic plane. What Population does it belong to, and why?

Question 66

Why is a variable star so convenient for measuring distances to very remote objects?

Question 67

Who was Henrietta Leavitt, and what did she do to help map the universe?

Question 68

Who discovered the period-luminosity relationship, and why was it so critical?

Question 69

We can estimate the mass of the Galaxy from observations of its ________ curve.

Question 70

Although astronomers refer to the Galaxy's disk as rotating, the motion is really due to the ________ motion of each of the objects in the disk.

Question 71

List at least one naked-eye observation that is consistent with the ancient idea that Earth is at the center of the Milky Way. List at least one naked-eye observation that is inconsistent with the notion that Earth is at the center of the Milky Way.

Question 72

How can Kepler's Third Law be used to estimate the mass of the galaxy?

Question 73

Of what is the Galactic halo presumed to be composed? What evidence supports this conclusion?

Question 74

Compare the speed of spiral density waves with the orbital speeds of stars in the visible part of the Galactic disk.

Question 75

How old is the Galaxy? How do we know this?

Question 76

Why is visible light a bad choice for studying the core of the Galaxy? What is better?

Question 77

What are the observational pieces of evidence that confirm the existence of a three-part structure (bulge, disk, halo) to the Milky Way Galaxy?

Question 78

How does content of elements heavier than helium vary between young and old stars? Why?

Question 79

Describe our location in the Milky Way.

Question 80

The Galactic center in ________ is best studied using radio and infrared observations.