Deck 23: The Milky Way Galaxy: a Spiral in Space

Question 1

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

Answer 1

True

Question 2

The Milky Way is simply our edge-on view of our home Galaxy.

Answer 2

True

Question 3

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

Answer 3

True

Question 4

Shapley found the Sun is located about halfway out the disk from the center of the disk of theGalaxy.

Question 5

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

Question 6

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

Question 7

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

Question 8

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

Question 9

Shapley correctly argued that the rotation of the spiral nebulae proved they could not be verydistant.

Question 10

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

Question 11

As Curtiss thought, our Milky Way is now known to be quite similar to the nearbyAndromeda Galaxy, M-31.

Question 12

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

Question 13

The instability strip includes many main sequence stars.

Question 14

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

Question 15

The Earth lies close to the center of the Galaxy.

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

Early in the 20th century, our Galaxy was estimated to be:

A)about 100,000 ly in diameter.
B)about 35,000 ly (10 kpc)in diameter.
C)about 10 million ly in diameter.
D)not much larger than our solar system.
E)about 2.5 million ly in diameter.

Question 22

Both RR Lyrae and Cepheid variable stars are stars that, when on the main sequence, wereconsidered to be:

A)low mass.
B)intermediate mass.
C)high mass.
D)zero-age main sequence.
E)blue stragglers.

Question 23

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 24

What perception of the Milky Way Galaxy did astronomers have in 1900?

A)They believed that the Earth rested inside concentric spheres, with the Milky Way stars fixedto the outermost sphere.
B)They believed that the Milky Way was one of billions of galaxies in the universe.
C)They believed that the Milky Way was the entire universe.
D)They believed that, because the Sun was at the center of the Milky Way, it was impossible tosee the rest of the universe.
E)They believed we were one of billions of galaxies in an expanding universe.

Question 25

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 26

Based on star counts, 100 years ago most astronomers thought:

A)we lay about 30,000 ly out from the center of the Galaxy.
B)we lay near the center of a disk about 10 kpc wide and 2 kpc thick.
C)we lay in a spiral arm of the largest galaxy in the universe.
D)we lay near the edge of the only galaxy in the universe.
E)we were not a part of any structure larger than the known solar system.

Question 27

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 disk
B)in the disk but at its outer edge
C)as Herschel found, very close to the Galactic center
D)above the disk and about one-third of the galactic radius from the center
E)in the disk and about one-half a galactic radius from the center

Question 28

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 29

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 30

From the center of the Milky Way, 10- kpc-long magnetized jets of high-energy particles areemitted.

Question 31

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 32

Which two classes of objects were critical to the Shapley-Curtiss Debate of 1920?

A)white dwarfs and red giants
B)open clusters and emission nebulae
C)globular clusters and spiral nebulae
D)emission nebulae and spiral nebulae
E)planetary nebulae and white dwarfs

Question 33

It was the distribution of ________ that showed Harlow Shapley we were nowhere near thecenter of the Milky Way in the 1920s.

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

Question 34

The region on the H-R diagram where pulsating variables occur is called the:

A)period-luminosity relation.
B)mass-luminosity relation.
C)instability strip.
D)horizontal branch.
E)main sequence appendix.

Question 35

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 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

All RR Lyrae stars have about the same:

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

Question 38

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

Question 39

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 40

Which of the following are most massive and luminous?

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

Question 41

The orbits of Population II 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 disk around a black hole.

Question 42

Star formation ceased first in the:

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

Question 43

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

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

Question 44

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 45

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 46

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

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

Question 47

The Harvard College Observatory Computers from c. 1880 into the early 20th century were:

A)the first digital computers.
B)not much different than cash registers.
C)functionally similar to the modern 4-function calculator.
D)a group of women who made important contributions to astronomy.
E)mechanically operated adding machines.

Question 48

In the Galactic halo, we do NOT find:

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

Question 49

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

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

Question 50

Detailed study of stellar spectra in 1897, which enabled the development of the H-Rdiagram, was performed by:

A)E.C. Pickering.
B)Harlow Shapley.
C)James Lick.
D)John Herschel.
E)Antonia Maury.

Question 51

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

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

Question 52

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 Galactic halo
C)at the very outer edge of the disk, but in the Galactic plane
D)in the disk in the inner region of the Sagittarius Arm
E)in the disk, and about halfway out from the center

Question 53

Detailed measurements of the disk and central bulge region of our Galaxy suggest our MilkyWay is a:

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

Question 54

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 55

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 56

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

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

Question 57

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

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

Question 58

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

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

Question 59

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 60

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 61

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 62

The leading explanation for the existence of spiral arms is:

A)shock waves from cyclic supernovae explosions.
B)shock waves 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 63

Some of the invisible matter in our Galactic halo has been shown to be white dwarfs by:

A)direct detection with optical telescopes, such as the Hubble Space Telescope.
B)direct detection with gamma-ray observations from the Fermi Telescope.
C)observations of Type I supernovae.
D)the gravitational microlensing technique.
E)watching white dwarfs in the Galactic halo pass in front of distant galaxies.

Question 64

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 65

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 $\mathrm { A } ^ { * }$

Question 66

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

A)Population I stars in the disk.
B)Population II stars in the halo.
C)hydrogen gas in the disk and spiral arms.
D)dark matter out in the halo.
E)the black hole in the Galactic Center.

Question 67

The gravitational microlensing technique has detected ________ in our Galactic halo.

A)planets
B)white dwarfs
C)clouds of neutral hydrogen
D)red giants
E)no visible matter

Question 68

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

Question 69

While yet unproven, the proposed WIMPS would be:

A)massive like neutrons, but more elusive than neutrinos.
B)made of only strong magnetic fields.
C)rapidly decaying due to the weak nuclear force.
D)changing charges and polarities too rapidly to pin down.
E)the basic building blocks of neutrons and protons.

Question 70

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 71

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

A) $10^6$ solar masses.
B) $10 ^ { 8 }$ solar masses.
C) $10^{10}$ solar masses.
D) $10^{11}$ solar masses.
E) $10^{12}$ solar masses.

Question 72

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

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

Question 73

These objects are no longer considered a good explanation for the dark matter in the Galactichalo.

A)WIMPs
B)MACHOs
C)black holes
D)clouds of cool, neutral hydrogen
E)brown dwarfs

Question 74

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 75

Low mass white dwarfs could account for how much of the dark matter in our Galactic halo?

A)up to 20%
B)at least 50%
C)all of it
D)no more than 1%
E)none

Question 76

The temperature of the innermost part of the spinning gas near our Galaxy's central blackhole is:

A)2.7 K.
B)300 K.
C)10,000 K.
D)over 1,000,000 K.
E)varying rapidly from 300 K to 1,000,000 K.

Question 77

Which sequence of formation in our Galaxy 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
E)Population I stars, Population II stars, Population III stars

Question 78

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 79

Density waves may explain:

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

Question 80

S2's orbital radius of 950 A.U. and an orbital period of 15 years are most consistent with S2being a star:

A)passing within a light-year of our solar system.
B)orbiting a 4 million solar mass object in the center of our Galaxy.
C)with a mass 4 million times the mass of our Sun.
D)in a globular cluster that has a mass about 4 million times the mass of our Sun.
E)being sucked into the black hole in the center of our Galaxy.