Deck 15: The Milky Way Galaxy

Question 1

Spiral arms are clearly visible features of galaxies because most sun-like stars in the disk are found there.

Answer 1

False

Question 2

A "grand-design" galaxy contains clear spiral arms with few spurs.

Answer 2

True

Question 3

The first stars formed in the Universe were composed of 90% hydrogen, 10% helium, and very little else.

Answer 3

True

Question 4

William and Caroline Herschel's map included four of the following hypotheses in their model of the galaxy. Which one was the exception?

A) They thought that the "holes in the sky" were caused by interstellar dust clouds.
B) They proposed that the galaxy had a disk shape.
C) They provided accurate measurements of the distances to stars.
D) They placed the Sun in the center of the galaxy.
E) They found errors caused by a lack of knowledge of the interstellar medium.

Question 5

  Figure 12-14(for the following questions)
The accompanying graph above clearly shows that ____.

A) Type I Cepheid variables are always brighter than Type II Cepheids
B) Type II Cepheid variables always have shorter pulsation periods than Type I Cepheids
C) Type I Cepheids are always more distant than Type II Cepheids
D) RR Lyrae stars can have longer pulsation periods than Cepheid variables
E) RR Lyrae stars are always dimmer than Cepheid variables.

Question 6

What property of a Cepheid variable can you determine if you know its period?

A) surface temperature
B) absolute magnitude
C) apparent magnitude
D) mass
E) radius

Question 7

The central bulge and the galactic disk of the Milky Way are often referred to as its spherical component.

Question 8

O and B stars are important spiral tracers.

Question 9

Stars in the central bulge of the galaxy follow elongated orbits tipped steeply to the plane of the disk.

Question 10

Harlow Shapley used observations of globular clusters to determine the position of the center of the galaxy.

Question 11

The center of the galaxy has been studied extensively using visible light.

Question 12

The black hole at the center of our galaxy is too large to be the remnant of a single star.

Question 13

Globular clusters are used as spiral tracers.

Question 14

The mass of the black hole in the center of the galaxy has been determined by observing the motion of stars orbiting it.

Question 15

Stars that formed in the very early stages of our galaxy's formation have high amounts of "metals."

Question 16

Harlow Shapley made the first accurate determination of the position of the center of the galaxy by studying ____.

A) globular clusters
B) open clusters
C) emission nebulae
D) spiral tracers
E) stellar associations

Question 17

William and Caroline Herschel attempted to make a map of the Milky Way galaxy by counting the number of stars visible in different directions.

Question 18

Based on Shapley's determination of the center of the galaxy, the Sun is located ____.

A) in the galactic halo
B) near the center of the galaxy
C) at the edge of the galactic bulge
D) in the middle portion of the galactic disk
E) at the outer edge of the galactic disk

Question 19

Most of the light that makes the hazy band of the "milky way" visible in the night sky comes from reflection and emission nebulae.

Question 20

Population I stars are younger than Population II stars.

Question 21

" Spurs" are probably the result of ____.

A) self-sustaining star formation
B) spiral density waves
C) differential rotation
D) the central galactic bar
E) the short lifetime of O stars

Question 22

The center of the Milky Way galaxy is in the direction of the constellation ____.

A) Sagittarius
B) Scorpius
C) Orion
D) Perseus
E) Andromeda

Question 23

Almost all of the gas and dust in the Milky Way is located in the ____.

A) halo
B) central bulge
C) disk
D) corona
E) center

Question 24

The mass of the Milky Way galaxy is a few ____.

A) million solar masses
B) hundreds of millions of solar masses
C) billion solar masses
D) hundreds of billions of solar masses
E) trillion solar masses

Question 25

  Figure 12-14(for the following questions)
Examine the accompanying graph. Harlow Shapley did not know that there are two categories of Cepheid variables; he was only familiar with those such as d Cepheii. Because of this, some of the Cepheid variables he observed ____.

A) were dimmer than he expected
B) were brighter than he expected
C) had a longer pulsation period than he expected
D) had a shorter pulsation period than he expected
E) were RR Lyrae variables

Question 26

Which of the following would be the closest estimate to the number of times the Sun has orbited the galactic center?

A) 1
B) 10
C) 25
D) 50
E) 100

Question 27

The Sun orbits the center of the galaxy about once every ____.

A) 200,000 years
B) 2,000,000 years
C) 20,000,000 years
D) 200,000,000 years
E) 2,000,000,000 years

Question 28

Spiral density wave theory and self-sustaining star formation are ways to explain why ____.

A) stars orbit the galaxy with different periods at different distances from the center
B) sun-like stars are evenly distributed through the disk of the galaxy
C) dark matter affects the orbit of stars outside the visible disk of the galaxy
D) molecular clouds are compressed forming young stars along spiral arms
E) the central bulge of the galaxy has a "bar" shape

Question 29

O stars must be formed in spiral arms because _____.

A) they do not live long enough to move out of the arm
B) the dust clouds they form from are only found there
C) all stars are formed in spiral arms
D) they are only found in spiral arms their gravitational forces takes them to that location
E) they are left behind and found in the region behind the spiral arm

Question 30

Dark matter is ___.

A) a cloud of black holes and brown dwarfs in the galactic halo
B) extremely cold, supermassive molecular clouds in the disk
C) an unknown type of mass that does not emit or absorb photons
D) the substance of which black holes are made
E) a theory to explain galactic formation that has been proven wrong

Question 31

____ are crucial in determining the distance to objects that are far away, but still in the Milky Way galaxy.

A) RR Lyrae stars
B) Cepheid variable stars
C) O and B stars
D) Emission nebulae
E) Supernovae

Question 32

Why is it so difficult to study the center of our galaxy?

A) Light from the center is lost in the glow of emission nebulae in this direction.
B) Interstellar dust blocks almost all light before it reaches Earth.
C) The exact position of the center is not known.
D) The center of the galaxy puts out very little radiation and is too dim to study.
E) The center of the galaxy is too far away for radiation to be detected by telescopes.

Question 33

In which area of the galaxy would you find stars with fairly circular orbits about the galactic center?

A) central bulge
B) halo
C) corona
D) disk
E) galactic center

Question 34

Spiral arms are obvious-easily-seen features-because they contain ____.

A) dense molecular clouds
B) atomic hydrogen clouds
C) sun-like stars
D) OB associations
E) supernovae

Question 35

A group of one hundred to a few thousand stars in a region of 25 pc in diameter that were created at the same time and our bound together by gravity is called a(n) ____.

A) associated cluster
B) open cluster
C) closed cluster
D) globular cluster
E) nebular cluster

Question 36

Which object would be absent in the galactic halo?

A) emission nebulae.
B) old main sequence stars
C) red giants
D) white dwarfs
E) Cepheid variables

Question 37

Why is it surprising that spiral arms are stable structures, lasting billions of years?

A) Differential rotation should tear the arms apart.
B) Gas and dust clouds should run out of material to make young stars.
C) Supernova explosions should disrupt the arms.
D) Globular clusters are continuously passing through the arms.
E) Gravity should pull the arms down into the center of the galaxy.

Question 38

The following objects are found in a spiral arm of a galaxy. Which is the exception?

A) population II stars
B) OB associations
C) emission nebulae
D) population I stars
E) clouds of gas and dust

Question 39

When you plot the position of sun-like stars, you will find that ___.

A) almost all sun-like stars are found in spiral arms
B) sun-like stars are found in and out of spiral arms
C) sun-like stars are left behind by the spiral arms that created them
D) sun-like stars are only found in the outer 2/3 of the disk
E) sun-like stars are only found in the inner 2/3 of the disk

Question 40

The center of our galaxy contains a very intense source of radio and X-ray radiation named Sgr A*. What is it about this source that supports the idea that the radiation comes from a black hole?

A) The radiation is strongly blueshifted, indicating that the object is collapsing.
B) The radiation is strongly redshifted indicating that the object is growing.
C) The radiation is coming from an incredibly small object.
D) Radio waves can only be produced by matter orbiting a black hole.
E) Only radiation from a black hole could penetrate the giant molecular clouds between Sgr A* and Earth.

Question 43

Galactic fountains are an important way to explain _____.

A) the distribution of metals in and above the plane of the galactic disk
B) the nature of dark matter
C) the formation of the galactic disk from the first stages of our galaxy
D) the generation and support of spiral density waves
E) why the spiral arms are active sites of star formation

Question 45

Describe the general features of the monolithic collapse hypothesis, with an explanation of how the two different stellar populations are explained by the model.

Question 46

A partial, or detached, segment of a spiral arm is referred to as a(n) " _______________."

Question 47

What is the monolithic collapse hypothesis unable to explain?

A) The randomly oriented, elongated orbits of stars in the bulge and halo
B) The circular motion of stars in the galactic disk
C) The difference in metallicity between the spherical component and the disk component of the galaxy
D) The elongated bar shape of the central bulge
E) The low density of material in the halo, compared to the central bulge

Question 48

How have astronomers determined the mass of the Milky Way's supermassive black hole?

Question 49

What observed feature of the Milky Way is better explained by the bottom-up hypothesis of galactic formation, as opposed to the monolithic collapse model?

A) The elongated shape of the central bulge of the galaxy
B) The different metallicities of the bulge and disk of the galaxy
C) The difference in age of globular clusters
D) The supermassive black hole found at center of the galaxy
E) The very little gas or dust that halo contains

Question 50

Which statement about stellar populations is correct?

A) Population I stars are found in the disk and halo; Population II stars are found in the bulge.
B) Population I stars are found in the halo; Population II stars are found in the disk and bulge.
C) Population I stars are found in the disk; Population II stars are found in the bulge and halo.
D) Population II stars are found in the disk; Population I stars are found in the bulge and halo.
E) Population I stars are found in the bulge; Population II stars are found in the disk and halo.

Question 51

Elements above hydrogen and helium come from _____.

A) the early stages of the Universe, before the formation of stars and galaxies
B) the collision of neutron stars and black holes
C) cooling and accretion of molecules in dense molecular clouds
D) the last phases of stellar evolution and stellar "death"
E) matter falling into supermassive black holes

Question 52

A "galactic fountain" is _____.

A) a stream of gas and dust being pulled into a galaxy as it forms
B) a jet of high-speed superheated material thrown out of the accretion disk around a black hole
C) a partial spiral arm formed by the collision of molecular clouds
D) a bubble of hot, metal-rich gas ejected from the disk by a burst of supernova
E) a stream of gas made from a star that has been torn apart while falling into a supermassive black hole

Question 53

_______________ variable stars are useful in measuring the distance to globular clusters.

Question 54

One of the most important features that must be explained by models during the formation of the galaxy is the ____.

A) formation of spiral arms
B) differences in age and metallicity of stars, especially in the halo
C) formation of the central supermassive black hole
D) accumulation of dark matter in the corona
E) importance of spiral arms to star formation

Question 55

The best explanation for the activity at the center of the galaxy is a(n) ____.

A) supercluster of O and B stars
B) black hole with a mass several thousand times the Sun's
C) giant atomic hydrogen cloud energized into a single, massive emission nebula
D) black hole with a mass several million times the Sun's
E) exotic object known as a "magnetar"

Question 56

O and B stars only occur in the galactic _______________.

Question 57

Why do astronomers conclude that the spiral arms are places of active star formation?

Question 58

At the center of our galaxy, ____.

A) material is available to make stars but the region is too cold to support star formation
B) large stars are formed by the collision of smaller stars
C) stars form at the same rate as they do in the spiral arms
D) there is no star formation since there is no gas present
E) there is evidence of recent, rapid star formation and supernova explosions

Question 59

What is the correct ordering of galactic components using the new bottom-up hypothesis starting from oldest to youngest?

A) galactic halo, average globular clusters, galactic disk
B) galactic halo, galactic disk, average globular clusters
C) average globular clusters, galactic halo, galactic disk
D) average globular clusters, galactic disk, galactic halo
E) galactic disk, average globular clusters, galactic halo.

Question 60

Objects used to map spiral arms are called spiral _______________.

Question 61

Astronomers refer to elements heavier than helium as _______________.

Question 62

What parts of the galaxy are considered to make up the "spherical component"?

Question 63

Discuss the evidence that supports the theory that there is a supermassive black hole at the center of our galaxy.

Question 64

Stars at different distances from the galactic center revolve with different periods, an effect called _______________ rotation.

Question 65

Sgr A* has been heavily studied using _______________ interferometry.

Question 66

Why was it difficult for astronomers to develop a clear understanding of the Milky Way until the last few decades?

Question 67

An astronomer named _______________ used globular clusters to locate the center of the galaxy. (enter last name only)

Question 68

Why are Cepheid variables so important to the study of the Milky Way Galaxy?

Question 69

Explain the reasoning that leads astronomers to believe that our galaxy is surrounded by a cloud of "dark matter".

Question 70

In the late 18th century, two astronomers, both with the last name of _______________, were the first to attempt to map the shape of the galaxy.

Question 71

Why do stars in the central bulge have a lower metallicity than stars in the disk?

Question 72

The galactic _______________ contains very little gas and dust, old stars, and globular clusters.

Question 73

Explain how giant molecular clouds give rise to spiral tracers as they move through a disk with spiral density waves.