Deck 15: The Milky Way Galaxy: a Spiral in Space

Question 1

It is harder to map the structure of the Milky Way in visible wavelengths than with radio and infrared waves.

Answer 1

True

Question 2

The instability strip is above the main sequence on the H- R diagram.

Answer 2

True

Question 3

William Herschel's original model for our Galaxy was based on counting stars.

Answer 3

True

Question 4

All Cepheid variables discovered so far lie in other galaxies.

Question 5

The instability strip shows that not all main- sequence stars are, in fact, stable.

Question 6

Shapley's measurements of the distances to open clusters vastly revised our understanding of our position in the Galaxy.

Question 7

The center of the Milky Way lies in the direction of the constellation Cygnus.

Question 8

Shapley found the globular cluster distribution equally concentrated all along the galactic plane.

Question 9

Because of their greater luminosity, RR Lyrae stars can be used at greater distances than can long- period Cepheids.

Question 10

The problem with visual observations of our Galaxy is the luminous gas haze.

Question 11

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

Question 12

Herschel's original disk model placed us close to the center of the Galaxy.

Question 13

All Cepheids are giants, but not all giant stars are Cepheid variables.

Question 14

The longer the period of pulsation for a Cepheid, the more massive and luminous the variable giant star is.

Question 15

The Milky Way is similar in many ways to M31, the Andromeda Galaxy.

Question 16

RR Lyrae stars pulsate, but with shorter periods and lower luminosities than Cepheids.

Question 17

Our Sun lies about 30,000 light-years out from the Galactic Center.

Question 18

All RR Lyrae stars are about 5 times the Sun's luminosity.

Question 19

The Earth lies close to the center of the Galaxy.

Question 20

William Herschel made the first map of the Galaxy about 200 years ago.

Question 21

Around us in the galactic plane, we find stars of a variety of ages and compositions.

Question 22

Stars within an emission nebula, such as M42, are considered Population I stars.

Question 23

Population I stars came billions of years before Population II stars.

Question 24

The two stellar populations are extremes, but, in fact, stars with intermediate properties are common.

Question 25

Halo stars are all Population II objects.

Question 26

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

Question 27

The thickness of the Galaxy near the Sun is about 1000 light-years.

Question 28

Planets are expected to be found orbiting most Population II stars.

Question 29

Cepheids are good examples of cataclysmic variable stars.

Question 30

The bright blue stars of Orion's Belt are Population I, while our yellow Sun is population II.

Question 31

Harlow Shapley mapped the Milky Way using the period- luminosity relationship for RR Lyrae stars.

Question 32

The globular star clusters are the most obvious examples of Population II around us.

Question 33

The stars of the halo are all old, and those of the disk are all new.

Question 34

21- cm radio waves allow us to map the distribution of hydrogen in spiral arms on the opposite side of the Galaxy.

Question 35

It would be very unlikely to find a massive, young star out in the halo.

Question 36

Herschel believed the Milky Way was a disk of stars, while Shapley found the extended halo more like a ball.

Question 37

The orbit of the Solar System around the Galaxy is similar to that of a planet, almost circular and in the galactic plane.

Question 38

The orbits of Population II stars and globular clusters are much like comets, rising high above the galactic plane with eccentric orbits.

Question 39

Shapley found the globular clusters were strongly concentrated toward Sagittarius.

Question 40

Like the RR Lyrae stars, Cepheids are all similar in luminosity, hence their use in measuring stellar distances.

Question 41

Which of the following are most massive and luminous?

A) RR Lyrae variables
B) Cepheid variables
C) T- Tauri variables
D) white dwarfs
E) brown dwarfs

Question 42

In structure, our Milky Way is most similar to

A) the Orion nebula.
B) the Large Magellanic Cloud.
C) M31, the Andromeda Galaxy.
D) an upscale version of a globular cluster.
E) none of these

Question 43

Between us and the Galactic Center lie about 100 billion solar masses.

Question 44

For finding the distances to globular clusters, Harlow Shapley used

A) planetary nebulae.
B) RR Lyrae variables.
C) eclipsing binaries.
D) Type I supernovae.
E) Population I classical Cepheids.

Question 45

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

Question 46

Most of the mass of our galaxy lies between Earth and the Galactic center.

Question 47

A star in the instability strip of the H- R diagram would

A) explode as a Type I supernova.
B) vary in both temperature and radius.
C) vary in temperature and radius, but not in brightness.
D) vary in brightness with an irregular pattern.
E) vary in temperature and brightness, but not in radius.

Question 48

Which of these variable stars would be classified as an RR Lyrae?

A) a K giant with a period of 14 days
B) a pulsar with a period of 0.14 seconds
C) a B supergiant with a period of 0.14 days
D) an F giant with a period of 14 hours
E) an M giant with a period of 140 days

Question 49

Our surveys of the Galactic Center are better done in infrared than visible light.

Question 50

The Sgr A* black hole may contain three million solar masses.

Question 51

The RR Lyrae stars all have periods of

A) less than a second.
B) several minutes.
C) several hours.
D) several days.
E) several weeks.

Question 52

Most of the dark matter in the Galaxy lies in the disk and galactic center.

Question 53

Why was Herschel's strategy for mapping our Galaxy flawed?

A) He used radio telescopes that didn't give enough resolution.
B) He assumed Earth was at the extreme edge of the Galaxy.
C) He used globular clusters, lying above the dust in the disc.
D) His infrared telescopes couldn't penetrate the dust clouds.
E) He relied on visual wavelengths, which are obscured by dust.

Question 54

Like our solar system, the whole Milky Way is about five billion years old.

Question 55

The spiral arms are sites of continuous new star formation, accounting for their blue color and pink emission nebulae.

Question 56

The density wave theory attempts to explain why the spiral arm structure persists over a long time.

Question 57

Dark matter has not been observed at any electromagnetic wavelength.

Question 58

The first attempt to map the Galaxy via star counts was done by

A) Edwin Hubble with the new 100" Mt. Wilson telescope in the 1930s.
B) Harlow Shapley with the RR Lyrae variables in 1920.
C) William Herschel in the late eighteenth century.
D) Edward Barnard with long exposure photos about 1900.
E) Galileo in 1612.

Question 59

All RR Lyrae stars have about the same

A) luminosity of about 100 Suns.
B) galactic location and speed.
C) locations in the centers of globular star clusters.
D) period of six days.
E) distance of 32 light-years.

Question 60

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

Question 61

The orbits of Population II stars have been compared to

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

Question 62

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

A) O and B stars
B) Population II giants like orange Arcturus
C) emission nebulae like M42
D) hot, young blue Population I stars
E) open clusters

Question 63

The period- luminosity relation is critical in finding distances with

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

Question 64

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 65

Which of these variable stars would be classified as a Cepheid?

A) an F giant with a period of 14 years
B) a G giant with a period of 14 hours
C) an M supergiant with a period of 140 days
D) a B supergiant with a period of 0.14 days
E) a K giant with a period of 14 days

Question 66

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

A) in the disc but at its outer edge
B) in the disc and about one- half a galactic radius from the center
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) at the outer edge of the galactic bulge but in the plane of the disc

Question 67

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

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

Question 68

What is true about the stellar populations in the Galaxy?

A) The main star forming regions are outside the Galactic plane.
B) Red stars are only found in the bulge.
C) Most open clusters are in the halo.
D) Only old stars are found in the halo.
E) The bluest stars are in the halo.

Question 69

What is one of the differences between Cepheids and RR Lyrae variables?

A) Cepheids are giants, but RR Lyrae stars are still on the main sequence.
B) The pulsations of RR Lyrae stars are much less regular than those of Cepheids.
C) The RR Lyrae stars have much shorter periods than Cepheids.
D) The period- luminosity relation holds only for RR Lyrae stars.
E) All Cepheids have the same brightness, but RR Lyrae stars vary greatly in luminosity.

Question 70

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

A) 225 million light-years.
B) 100,000 light-years.
C) 8 kpc.
D) 100 billion parsecs.
E) 8,000 light-years.

Question 71

Which statement is true?

A) Population II stars probably have terrestrial planets around them.
B) Population I stars are the brightest stars in the globular clusters.
C) Our Sun is a Population II star.
D) Population I stars lie outside the galactic disc.
E) The bright blue stars that dominate the sky are Population I stars.

Question 72

Galactic disks appear blue because

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

Question 73

Which statement about Population II is false?

A) They formed first as the Galaxy formed.
B) They are made of almost nothing but hydrogen and helium.
C) At almost five billion years old, our Sun must belong to this older Population.
D) Their orbits around the Galaxy resemble those of comets.
E) The globular clusters are their most obvious groupings.

Question 74

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

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

Question 75

In our location in the Milky Way, the galactic disk is only about ly thick.

A) 10
B) 100
C) 1,000
D) 10,000
E) 100,000

Question 76

The tidal streams mapped in the Halo are similar to _ _ in our solar system.

A) meteor swarms in old comet orbits
B) the rings around the jovians
C) the moons orbiting planets
D) the asteroid belt between Mars and Jupiter
E) the solar wind

Question 77

Which of these objects have NOT been found in the Galactic Halo?

A) Population II stars
B) emission nebulae
C) Cepheid variables
D) globular clusters
E) RR Lyrae variables

Question 78

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

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

Question 79

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 80

Harlow Shapley found the Milky Way was

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