Deck 22: The Milky Way

Question 1

What did Harlow Shapley discover about globular clusters that allowed him to determine the size of the galaxy and the Sun's location within it?

A)The clusters are confined to a thin plane
B)The clusters are all located at the same distance from the Sun
C)The center of the distribution of clusters is far from the Sun
D)All of the clusters are located in a region a few parsecs across

Answer 1

The center of the distribution of clusters is far from the Sun

Question 2

How did Harlow Shapley discover that our Sun is not at the center of the galaxy?

A)By detecting radio radiation from the galactic center
B)By measuring the orbital speed of the Sun around the galactic center
C)By determining the distribution of globular clusters
D)By comparing our galaxy with the Andromeda galaxy

Answer 2

By determining the distribution of globular clusters

Question 3

What kind of star is located at the center of an HII region?

A)A hot one
B)A cool one
C)A young one
D)A main sequence star

Answer 3

A hot one

Question 4

The distance to the center of the galaxy is about

A)8 astronomical units
B)8 parsecs
C)8 light years
D)8 kiloparsecs

Question 5

The distance to the center of our galaxy can be found from

A)The Cepheid variables there
B)The parallax of the black hole located there
C)Radar measurements
D)The distribution of globular clusters in space

Question 6

We cannot see the other side of the galaxy primarily because our view is blocked by

A)Too many stars
B)Glowing interstellar gas
C)Interstellar dust
D)Planetary nebulae and supernova remnants

Question 7

What property of globular clusters made it possible to study them in order to discover important information about the structure of the Milky Way galaxy?

A)Nearly all of them are located in the core of the galaxy
B)Nearly all of them are located at the same distance from the Sun
C)Most of them are located in the spiral arms of the galaxy
D)Their distribution is centered on the center of the galaxy

Question 8

Interstellar dust grains produce

A)Radio emission at a wavelength of 21 cm
B)Interstellar absorption lines in the spectra of distant stars
C)Extinction and reddening of the light from distant stars
D)Ultraviolet radiation responsible for HII regions

Question 9

The 21 cm line is emitted by

A)Hydrogen atoms
B)Interstellar dust
C)A gas of hot protons and electrons
D)CO molecules

Question 10

The hydrogen in an HII region is

A)In molecular form
B)Very cool
C)Ionized
D)In liquid form

Question 11

Why are HII regions red in color?

A)They contain considerable quantities of dust
B)They emit hydrogen emission lines
C)They are moving away from us at high speed
D)Twenty-one cm photons are red in color

Question 12

What kind of object creates an evacuated,very hot bubble in the interstellar gas?

A)A red giant star
B)A black hole
C)A supernova
D)A globular cluster

Question 13

What assumption about globular clusters did Harlow Shapley make in order to determine the location of and distance to the center of the Milky Way?

A)The globular clusters are distributed about the center of the Milky Way
B)All globular clusters have the same age
C)All globular clusters are moving away from us
D)None of the clusters we see are located in the Milky Way

Question 14

What effect do interstellar dust particles have on the appearance of a distant star?

A)They make it look bluer and brighter
B)They make it look bluer and dimmer
C)They make it look redder and brighter
D)They make it look redder and dimmer

Question 15

The bluish color of the nebulosity around the Pleiades is produced by

A)Starlight reflected by interstellar grains
B)Emission lines of hot neon gas
C)Continuous radiation from very hot gas
D)Synchrotron radiation.

Question 16

What atom produces 21 cm radiation?

A)Hydrogen
B)Nitrogen
C)Silicon
D)Oxygen

Question 17

A reflection nebula is produced when the light from a star is scattered by interstellar

A)Electrons
B)Atoms
C)Molecules
D)Dust particles

Question 18

Astronomers of about the year 1900 didn't know of the existence of interstellar dust.As a result they

A)Underestimated the size of the galaxy.
B)Thought the globular clusters were located in other galaxies
C)Did not believe that our galaxy had spiral arms
D)Believed stars were much bluer than they really are

Question 19

What keeps the matter in an HII region ionized?

A)Ultraviolet radiation from a star or stars
B)Chemical reactions
C)Collisions between gas clouds
D)Beams of electrons

Question 20

Why has the 21 cm emission line been especially useful for studying the structure of the Milky Way galaxy?

A)Stars emit very strongly at 21 cm
B)The 21 cm radiation travels to us at the speed of light
C)Twenty-one cm emission is produced only in the core of the galaxy
D)Twenty-one cm radiation is unaffected by interstellar dust

Question 21

How do we know that the Milky Way has a spiral structure?

A)By plotting the distances and directions of objects known to be in spiral arms
B)By viewing the galaxy from a point well above its plane
C)By observing the changing conditions as the sun enters a spiral arm
D)By observing the gravitational influence of the arms on nearby galaxies

Question 22

Which of the following kinds of objects are found in the halo of the galaxy?

A)Globular clusters
B)Supernovae
C)Spiral arms
D)HII regions

Question 23

Consider a star that orbits the galaxy at half the Sun's distance.If that star has the same orbital period as the Sun,how does the mass interior to the star's orbit compare to the mass interior to the Sun's orbit?

A)The same
B)One-eighth
C)One-quarter
D)One-half

Question 24

In order to make a scale model of the galaxy in which stars are represented by salt grains,how far apart would neighboring salt grains be?

A)1000 miles
B)10 miles
C)100 yards
D)1 yard

Question 25

Which of the following is true of spiral arms?

A)They contain a very large density of solar-type stars
B)Once a star enters a spiral arm it remains stuck there
C)Stars form in spiral arms
D)Spiral arms are spun off of the core of the galaxy

Question 26

Which of the following is a true statement about the spiral arms of our galaxy?

A)They are made of matter blown outward from the center of the galaxy
B)Once a star falls into a spiral arm it stays there forever
C)They are the crests of a density wave
D)They have not yet completed a single rotation about the galactic center

Question 27

Which of the following statements describes the mass in the outer part of the Milky Way (beyond the orbit of the sun)?

A)It emits a surprisingly small amount of light
B)There is essentially no mass out there
C)There is no spiral arm structure in the outer galaxy
D)The outer part of the galaxy is rapidly evaporating into intergalactic space

Question 28

Which of the following objects is not found primarily in the spiral arms of a galaxy?

A)White dwarf stars
B)HII regions
C)Supernovae
D)O and B stars

Question 29

Which of the following must be known in order to determine the amount of galactic mass that lies within the Sun's orbit?

A)The Sun's distance from the center and orbital period
B)The Sun's mass and orbital speed
C)The Sun's distance from the center and the size of its orbit
D)The Sun's mass and its distance from the center

Question 30

How would our estimate of the mass of the galaxy be changed if it were discovered that the period of revolution of the Sun is actually twice as long as it is now thought to be?

A)It would be increased
B)It would be decreased
C)It would be unchanged
D)The Sun's period is irrelevant to determining the mass of the galaxy

Question 31

The orbital period of the Sun and the distance of the Sun from the center of the galaxy can be used to calculate which of the following?

A)The mass inside the Sun's orbit
B)The age of the galaxy
C)The age of the Sun
D)The distance to the Andromeda galaxy

Question 32

Which of the following statements about the density wave model for spiral arms is FALSE?

A)Material,once it enters a spiral arm,remains there permanently
B)Star formation occurs in spiral arms
C)Once started,spiral structure lasts a long time
D)Spiral arms are not winding up as time passes

Question 33

The mass of the galaxy has been found by

A)Counting the stars it contains
B)Determining its gravitational force on nearby galaxies
C)Estimating the number of interstellar clouds it contains
D)Applying Kepler's third law to the Sun's orbit

Question 34

Which of the following types of objects are mostly found in the spiral arms of the galaxy?

A)O and B stars
B)Solar type stars
C)Pulsars
D)Brown dwarfs

Question 35

The rotation curve of the Milky Way galaxy is non-Keplerian at large distances from the center.This is evidence for

A)Rigid body rotation throughout the galaxy
B)Large amounts of unseen mass in the outer galaxy or halo
C)Gravitational waves in the galaxy
D)Spiral arms
E)Peculiar velocities of distant stars.

Question 36

About how long does it take for the Sun to complete one trip around the galaxy?

A)25 thousand years
B)2.5 million years
C)250 million years
D)25 billion years

Question 37

Where are globular clusters located in the galaxy?

A)In the nucleus
B)In the disk
C)In the spiral arms
D)In the halo

Question 38

Which of the following is the best description of the rotation curve of the galaxy between the Sun's orbital distance and twice the Sun's orbital distance?

A)Flat
B)Rising steadily
C)Falling steadily
D)Many large fluctuations in orbital speed with distance

Question 39

What evidence do we have that there is hidden mass in the galaxy?

A)Cool clouds of hydrogen
B)RR Lyrae variable stars in globular clusters
C)Non-Keplerian (flat)rotation curve at large radii
D)Missing neutrinos from the Sun
E)Dusty regions in the plane

Question 40

Why are most O and B stars found in the arms of the galaxy?

A)They are magnetically bound to the spiral arms
B)They ride on the crests of the density wave
C)They are short-lived stars that form in spiral arms
D)They have been ejected recently from the center of the galaxy

Question 41

Which of the following has NOT happened during the evolution of the galaxy?

A)The abundance of heavy elements has increased
B)The thickness of the galaxy has decreased.
C)The galaxy has rotated many times
D)The number of stars has dropped steadily

Question 42

The oldest stars in the galaxy are found

A)In globular clusters in the halo
B)At the center of the galaxy
C)On the front rim of spiral arms
D)In the galactic disk

Question 43

Why can't we see visible radiation from the central region of the galaxy?

A)No visible light is emitted by the central region of the galaxy
B)Interstellar dust blocks our view
C)Too many stars are in the way
D)Gravity curves the light away from the earth and Sun

Question 44

The stars in globular clusters are

A)Young and metal rich
B)Young but metal poor
C)Old and metal poor
D)Old and metal rich

Question 45

Which of the following best describes the way that our galaxy has changed throughout its history?

A)It has grown flatter and richer in heavy elements
B)It has grown less flattened and richer in heavy elements
C)It has grown flatter and poorer in heavy elements
D)It has grown less flattened and poorer in heavy elements

Question 46

Where are stars being formed in the galaxy?

A)In the spiral arms
B)In globular clusters
C)In the nucleus
D)In the halo

Question 47

The distance of the Sun from the galactic center is considered to be around what value?

A)2.5 kpc
B)5.2 kpc
C)8.5 kpc
D)9.3 kpc

Question 48

The best type of telescope for probing the galactic center region is a(n)

A)Large refraction telescope optical.
B)Ultraviolet telescope
C)Large,space-based optical telescope
D)Infrared telescope

Question 49

Evidence for dark matter in the galaxy comes from ___________ .

A)the flatness of the rotation curve.
B)direct observation of dark matter.
C)distant galactic jets,which eject dark matter in high concentrations.
D)none of the above.

Question 50

Which of the following is evidence for violent activity at the center of the galaxy?

A)The occurrence of supernovae in the spiral arms
B)The flattened shape of the galaxy
C)The shell of expanding gas 3 kpc from the center
D)Thousands of pulsars in the center of the galaxy

Question 51

The halo population of stars is

A)Very young with much dust and gas
B)Quite old,containing few metals
C)Mixed,with about equal populations of young and old stars
D)Mostly second and third generation stars
E)Nearly all stellar remnants at the present epoch

Question 52

Which of the following is not necessarily different in Population I and Population II stars?

A)Chemical abundances
B)Location in the galaxy
C)Age
D)Luminosity

Question 53

Which of the following is an example of population II?

A)A supernova
B)A globular cluster
C)An HII region
D)A molecular cloud

Question 54

The 3 kpc arm is

A)A spiral arm rotating the wrong way about the nucleus
B)Gas falling inward toward the center of the galaxy
C)Evidence of explosive activity at the nucleus of the galaxy
D)The arm containing most of the naked eye stars we see

Question 55

The galaxy has become enriched in heavy elements since it formed.What is responsible for the enrichment?

A)Nuclear reactions in interstellar clouds
B)The infall of heavy elements from intergalactic space
C)The transformation of cosmic rays into heavy elements
D)Nuclear reactions in stars,followed by stellar mass loss

Question 56

The velocity of the sun in its orbit around the galactic center is considered to be around what value?

A)150 km/sec
B)220 km/sec
C)340 km/sec
D)541 km/sec

Question 57

The density wave theory for the formation of spiral arms predicts that

A)The arms will wrap up in the lifetime of the galaxy.
B)The arms contain newborn stars triggered by the density waves
C)The arms are caused mainly by tidal interactions
D)Elliptical galaxies will eventually become barred spirals
E)The arms have a high density of solar-type stars

Question 58

Our Milky Way Galaxy is considered to have how many main spiral arms?

A)1
B)2
C)4
D)6

Question 59

The first stars that formed in the galaxy

A)Were located in the disk of the galaxy
B)Never ignited hydrogen in their cores
C)Contained only small amounts of heavy elements
D)Have all escaped from the galaxy into intergalactic space

Question 60

What evidence do we have that there is a massive black hole at the center of the Milky Way?

A)There is rapidly rotating gas very close to the center
B)It is very dark there
C)Interstellar dust is being pulled into the central region of the Milky Way
D)The density of stars increases as distance from the center decreases

Question 61

The ages of galactic components _________ as their distances from the galactic plane increases.

A)increases
B)decreases
C)stays the same
D)increases,then decreases

Question 62

Galactic flattening is similar to what physical structure?

A)The shape of an irregular galaxy.
B)Solar system formation with an ecliptic plane containing planets.
C)Rotations in a binary system.
D)The earth's equatorial bulge.

Question 63

The components of the galaxy,from youngest to oldest are _________ .

A)thin disk,thick disk,Halo.
B)Halo,thick disk,thin disk.
C)thick disk,Halo,thin disk.
D)Halo,thin disk,thick disk.