Deck 15: The Milky Way Galaxy

Question 1

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) 21cm radiation from H I regions.
D) the rotation curve of the galaxy.
E) the energy produced by Sagittarius A*

Answer 1

observations of globular clusters.

Question 2

Halo stars located in the disk are easy to detect because they

A) are the only low mass stars in the disk.
B) are only found in globular clusters.
C) are primarily O and B supergiants.
D) move at an angle across the disk.
E) emit cosmic rays.

Answer 2

move at an angle across the disk.

Question 3

Population II stars

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

Answer 3

III & IV

Question 4

The orbits of population I stars

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

Question 5

The traditional monolithic collapse theory for the formation of the Milky Way Galaxy suggests that our galaxy formed

A) as material accreted around a massive black hole currently at the center of our galaxy.
B) from a large cloud of material that formed stars and star clusters and slowly flattened to a disk.
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 6

The magnetic field of the galaxy

A) is stronger than the magnetic field of the sun.
B) traps cosmic rays in the disk of the galaxy.
C) creates the spiral density waves that initiate star formation.
D) forces the halo stars to follow highly inclined orbits.
E) produces 21-cm radiation that allows us to map the spiral arms.

Question 7

The first stars to form in our galaxy

A) had circular orbits.
B) had highly elliptical orbits.
C) were population I stars.
D) all had orbits in the same plane.

Question 8

Galaxy spiral arms are traced out (outlined)by stars which are

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

Question 9

Diagram 15-1

-Refer to Diagram 15-1.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 10

Our galaxy is suspected to be surrounded by a galactic 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) rotates faster than expected in its inner region.
D) rotates more slowly than expected in its inner region.
E) is much flatter than expected.

Question 11

The nuclear bulge of our galaxy

A) contains stars that are primarily population I stars.
B) contains relatively large amounts 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) a,b,and d

Question 12

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 13

Herschel's grindstone and Kapteyn's star system were 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 14

Younger stars formed not so long ago have more heavy elements than stars formed early in the history of our Galaxy because

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

Question 15

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 16

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 17

A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their mutual gravity cannot hold them together is called

A) a globular cluster.
B) an open cluster.
C) an association.
D) a spherical component.
E) an accretion disk.

Question 18

Compared to population II,the larger abundance of atoms more massive than hydrogen and helium in 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 19

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 galaxy.
E) was completed by William and Caroline Herschel.

Question 20

Diagram 15-1
Refer to Diagram 15-1.A type I Cepheid has been located in an open cluster.The period of the Cepheid variable is 30 days,and the variable's apparent visual magnitude is 10.What is the distance to this open cluster?

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

Question 21

The energy source at the center of our galaxy

A) is not visible at optical wavelengths.
B) produces gamma rays.
C) must be less than 10 AU in diameter.
D) all of the above
E) none of the above

Question 22

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 23

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 24

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

Question 25

How did Harlow Shapley use the period-luminosity relationship of Cepheid 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 distance to individual Cepheid variables free floating in the halo.
C) He found the distance to open clusters found throughout the disk of the galaxy.
D) He found the distance to globular clusters distributed about the center of the galaxy.

Question 26

Radio maps of our galaxy show spiral arms because the

A) arms have high Doppler shifts.
B) gas in the spiral arms is hot enough to emit photons.
C) dust in spiral arms is more dense than it is between the spiral arms.
D) gas in spiral arms is more dense than it is between the spiral arms.
E) stars in the spiral arms emit most of their energy at radio wavelengths.

Question 27

What behavior do galactic rotation curves exhibit to suggest the existence of dark matter?

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 28

Astronomers before Shapely underestimated the size of the Milky Way galaxy because they lacked large enough telescopes.

Question 29

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 30

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

A) all spiral arms would be dust free.
B) all galaxies would have grand design spiral patterns.
C) the Milky Way would be more massive than observed.
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 31

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 32

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 33

How does the traditional monolithic collapse theory of the formation of the galaxy explain the origin of globular clusters?

A) They formed in the disk and later were ejected to the halo.
B) They formed in other galaxies and were captured by close interactions.
C) They build over time from the collision of stars in the halo.
D) They formed early on during the free-fall collapse of the proto-galactic material.

Question 34

A several million solar mass ____ is thought to be at the center of our galaxy.

A) spiral arm
B) globular cluster
C) planet
D) black hole

Question 35

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 36

Our Milky Way Galaxy is about...

A) 1 light year across
B) 10 light years across
C) 100 light years across
D) 1000 light years across
E) 100,000 light years across

Question 37

This is a "thought" question.Why are few galaxies outside our own galaxy seen 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) the Big Bang has blown galaxies away from those directions

Question 38

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 39

The disk of the Milky Way is approximately 20,000 ly in diameter.

Question 40

If a star with a peculiar space motion with respect a typical disk star is found what other property would you expect it to have?

A) Low luminosity.
B) Poor metal content compared to the Sun.
C) Old age.
D) All of the above.

Question 41

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

Question 42

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

Question 43

Population II stars contain more metals than Population I stars.

Question 44

The orbits of halo stars are typically circular and have a low inclination with respect to the disk.

Question 45

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

Question 46

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

Question 47

Henrietta Leavitt discovered the period-luminosity relationship for ____________________.

Question 48

Spiral tracers tend to be old,luminous stars.

Question 49

The center of our galaxy shows signs of past eruptions.

Question 50

The density wave theory explains spurs and branches along the spiral arms.

Question 51

Giant molecular cloud complexes are located in spiral arms.

Question 52

The rapid rotation in the outer disk suggests that our galaxy is more massive than previously thought.

Question 53

Old stars are poor in heavy atoms because there were no previous generations of stars.

Question 54

The disk of the galaxy is older than the halo.