Name: 
 

Test - Chapters 9, 10, 11, 12, 13 & 14



True/False
Indicate whether the statement is true or false. (1-Point Each)
 

 1. 

Stars swell into giants when hydrogen is exhausted in their centers.
 

 2. 

The disk of the galaxy is older than the halo.
 

 3. 

The center of our galaxy is located in the direction of the constellation of Orion.
 

 4. 

Pulsars could not be pulsating stars because the pulses are too short.
 

 5. 

The rapid fluctuations of quasars show that the objects must be very small.
 

 6. 

Giant molecular cloud complexes are located in spiral arms.
 

 7. 

Some quasars have fuzz around them that produces spectra similar to normal galaxies.
 

 8. 

We expect neutron stars to spin rapidly because they conserve angular momentum.
 

 9. 

The thermal motions of the atoms in a gas cloud can make it collapse to form a protostar.
 

 10. 

Cepheid variable stars are more luminous than the sun.
 

 11. 

The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus.
 

 12. 

Hydrostatic equilibrium refers to the balance between weight and pressure.
 

 13. 

When two galaxies collide, they pass through each other and their stars almost never collide.
 

 14. 

The sun will eventually become a supernova.
 

 15. 

Type II supernovae are believed to occur when the cores of a massive stars collapse.
 

 16. 

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

 17. 

Young star clusters have bluer turn-off points than old clusters.
 

 18. 

Once a star ejects a planetary nebula, it becomes a white dwarf.
 

 19. 

Because more massive stars have more gravitational energy, they can fuse heavier nuclear fuels.
 

 20. 

The look-back time is numerically equal to the distance to a galaxy in light-years.
 

 21. 

Double-lobed radio galaxies appear to be emitting jets of gas and radiation.
 

 22. 

Spiral tracers tend to be old, luminous stars.
 

 23. 

The sun makes most of its energy by the CNO cycle.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question. (3-Points Each)
 

 24. 

A planetary nebula is
a.
a cloud of hot gas surrounding a planet.
b.
the expelled outer envelope of a medium mass star.
c.
a nebula within which planets are forming.
d.
produced by a supernova explosion.
e.
produced by a nova explosion.
 

 25. 

The chemical abundance of population I stars
a.
depends on the temperature of the star.
b.
indicates that they were formed before the population II stars.
c.
indicates that the material they formed from had been enriched with material from supernovae.
d.
indicates that they contain very few heavy metals compared to halo stars.
e.
depends on the mass of the star.
 

 26. 

The orbits of population I stars

I.
are confined to disk of the galaxy.
II.
are very elliptical.
III.
are nearly circular.
IV.
are randomly inclined to the disk of the galaxy.
a.
I & IV
b.
IV
c.
II & IV
d.
I & III
e.
I
 

 27. 

The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that
a.
they are powered by magnetic fields.
b.
they are powered by the rapid rotation of the galaxy.
c.
they are excited by radiation from nearby galaxies.
d.
they are formed by material falling into the galaxy.
e.
they are created by jets from the galaxy.
 

 28. 

Due to the dust in the interstellar medium, a star will appear to an observer on Earth to be
a.
brighter and cooler than it really is.
b.
unchanged in brightness or apparent color.
c.
brighter and hotter than it really is.
d.
fainter and redder than it really is.
e.
fainter and bluer than it really is.
 

 29. 

Protostars are difficult to observe because
a.
they radiate mainly in the infrared.
b.
the protostar stage is very short.
c.
they are surrounded by cocoons of gas and dust.
d.
all of the above
e.
they are all so far away that the light hasn't reached us yet.
 

 30. 

When material expanding away from a star in a binary system reaches the Roche surface
a.
all of the material will accrete on to the companion.
b.
the material will start to fall back toward the star.
c.
the material is no longer gravitationally bound to the star.
d.
the material will increase in temperature an eventually undergo thermonuclear fusion.
e.
c and d
 

 31. 

That the radio lobes radiate synchrotron radiation indicates that
a.
high speed electrons are spiraling through a magnetic field.
b.
the source of the radio energy is rotating rapidly.
c.
the central galaxy must rotate about two nearly perpendicular axes.
d.
the central galaxy must be a giant elliptical galaxy.
e.
the source of the radio jets must be a black hole.
 

 32. 

Radio maps of the spiral arms of our galaxy
a.
reveal that our galaxy is a grand design spiral.
b.
reveal that the sun is currently located in the center of a spiral arm.
c.
map the location of dense neutral hydrogen clouds.
d.
map the location of Hot O and B stars by the radio radiation they emit.
e.
reveal that the spiral arms are winding up and growing closer together.
 

 33. 

The density of a _________ is greater than the density of a _________.
a.
pulsar neutron star
b.
white dwarf black hole
c.
pulsar white dwarf
d.
white dwarf neutron star
e.
neutron star black hole
 

 34. 

If the spiral density wave were the only thing producing spiral arms, it would be expected that
a.
the halo component of the Milky way would show spiral arms as well.
b.
all galaxies would have only two smooth spiral arms.
c.
all spiral arms would be dust free.
d.
the Milky Way wouldn't have any spiral arms.
e.
the Milky Way would be more massive than observed.
 

 35. 

The energy source at the center of our galaxy
a.
must be less than 10 AU in diameter.
b.
is not visible at optical wavelengths.
c.
produces x rays.
d.
all of the above
e.
none of the above.
 

 36. 

Our galaxy is suspected to be surrounded by a galactic corona because the disk of the galaxy
a.
is much flatter than expected.
b.
rotates more slowly than expected in its inner region.
c.
rotates faster than expected in its inner region.
d.
rotates faster than expected in its outer region.
e.
rotates more slowly than expected in its outer region.
 

 37. 

Quasars must be small because they
a.
are surrounded by quasar fuzz.
b.
are very luminous.
c.
radiate huge amounts of energy.
d.
have high radial velocities.
e.
fluctuate rapidly.
 

 38. 

_________ first noticed that for Cepheid variable stars, there was a direct relation between the luminosity and the period of the variation in their brightness.
a.
Carl Sagan
b.
Annie Cannon
c.
John Glenn
d.
Henrietta Leavitt
e.
Edwin Hubble
 

 39. 

Radio maps of our galaxy show spiral arms because
a.
the gas in the spiral arms is very hot.
b.
the stars in the spiral arms emit most of their energy at radio wavelengths.
c.
the gas in spiral arms is denser.
d.
the arms have larger Doppler shifts.
e.
the dust in spiral arms is denser.
 

 40. 

The traditional theory states that the galaxy formed
a.
as two massive galaxies collided.
b.
as a large spherical cloud of gas that was rotating very slowly.
c.
from material that had been ejected in the violent explosion of a dying galaxy.
d.
from a large cloud of material that broke off a larger galaxy.
e.
as a result of mergers between several smaller groups of gas, dust, and stars.
 

 41. 

The first pulsar was discovered by _________ in November of 1967.
a.
Isaac Newton
b.
Jocelyn Bell
c.
Albert Einstein
d.
Walter Baade
e.
Edwin Hubble
 

 42. 

The Chandrasekhar limit tells us that
a.
stars with a mass less than 0.5 solar masses will not go through helium flash.
b.
not all stars will end up as white dwarfs.
c.
neutron stars of more than 3 solar masses are not stable.
d.
white dwarfs must contain more than 1.4 solar masses.
e.
accretion disks can grow hot through friction.
 

 43. 

Giant and supergiant stars are rare because
a.
the giant and supergiant stage is unstable.
b.
helium flash destroys many of the stars before they can become giants and supergiants.
c.
they do not form as often as main sequence stars.
d.
the giant and supergiant stage is very short.
e.
helium is very rare.
 

 44. 

A star will experience a helium flash if
a.
it is more massive than about 6 solar masses.
b.
its mass on the main sequence was less than 0.1 solar masses.
c.
its core contains oxygen and helium.
d.
its core is degenerate when helium ignites.
e.
it is a supergiant.
 

 45. 

A Type I supernova is believed to occur when
a.
a white dwarf exceeds the Chandrasekhar limit.
b.
the cores of massive stars collapse.
c.
neutrinos in a massive star become degenerate and form a shock wave that explodes the star.
d.
the core of a massive star collapses.
e.
carbon detonation occurs.
 

 46. 

The event horizon
a.
is located at the point where synchrotron radiation is created around a pulsar.
b.
has a radius equal to the Schwarzschild radius.
c.
is a crystalline layer.
d.
marks the inner boundary of a planetary nebula.
e.
is believed to be a singularity.
 

 47. 

A white dwarf is composed of
a.
degenerate iron nuclei.
b.
hydrogen nuclei and degenerate electrons.
c.
helium nuclei and normal electrons.
d.
a helium burning core and a hydrogen burning shell.
e.
carbon and oxygen nuclei and degenerate electrons.
 

 48. 

The rotation curve of a galaxy can be used to determine
a.
the mass of the galaxy.
b.
the radius of the galaxy.
c.
the relative amount of gas and dust in the galaxy.
d.
the relative number of hot young stars in the galaxy.
e.
the luminosity of the galaxy.
 

 49. 

What was the first evidence that quasars were different from any objects observed before they were discovered?
a.
The first quasars were seen to have fuzz.
b.
The large red shifts originally indicated that they were orbiting the center of the Milky Way.
c.
The spectra of quasars looked like that of an M dwarf.
d.
Quasars emitted radio energy like active galaxies, but appeared to be point sources at visible light.
e.
Quasars showed significant gravitational lens effects.
 

 50. 

Stars are born in
a.
HII regions.
b.
the local bubble.
c.
reflection nebulae.
d.
the intercloud medium.
e.
dense molecular clouds.
 

 51. 

A megaparsec is equivalent to
a.
3,260,000 light-years.
b.
3.26 light-years.
c.
206,265 light years.
d.
the diameter of the Milky Way galaxy.
e.
206,265 AU.
 

 52. 

Good spiral tracers are all

I.
very old.
II.
very young.
III.
very luminous.
IV.
moving with large radial velocities.
a.
I, III, & IV
b.
I & IV
c.
II & III
d.
I & III
e.
II & IV
 

 53. 

Although neutron stars are very hot, they are not easy to locate because
a.
they are only found in other galaxies.
b.
most lie beyond dense dust clouds.
c.
solid neutron material cannot radiate photons.
d.
light does not escape from their event horizon.
e.
they have small surface areas.
 

 54. 

__________ is the thermonuclear fusion of hydrogen to form helium operating in the cores of massive stars on the main sequence.
a.
Hydrostatic equilibrium
b.
The neutrino process
c.
The CNO cycle
d.
The proton-proton chain
 

 55. 

Nucleosynthesis
a.
is the process by which energy is produced at the center of the galaxy.
b.
describes how the magnetic field of the galaxy traps cosmic rays.
c.
is the process by which hydrogen and helium are converted into heavier elements.
d.
describes the structure of a globular cluster.
e.
describes the method by which neutral hydrogen produces 21 cm radiation.
 

 56. 

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.
an association.
b.
a globular cluster.
c.
an open cluster.
d.
an accretion disk.
e.
a spherical component
 

 57. 

Galactic cannibalism refers to
a.
binary galaxies.
b.
galaxies drawing in gas from the intergalactic medium.
c.
the merging of galaxies.
d.
the destruction of a galaxies globular clusters by the galaxies nucleus.
e.
none of these
 

 58. 

The look-back time is
a.
how long the light from an object takes to reach Earth.
b.
numerically equal to the distance in light-years.
c.
smaller for more distant objects.
d.
all of the above
e.
a and b above
 

 59. 

As material flows into a black hole
a.
the material will experience time dilation.
b.
the material will become hotter.
c.
the material will produce an absorption spectrum.
d.
the material will appear to us to fall into the black hole very rapidly.
e.
a and b
 

 60. 

The search for black holes involves searching for
a.
pulsars with periods less than one millisecond.
b.
single stars that emit large amounts of x-rays.
c.
large spherical regions from which no light is detected.
d.
x-ray binaries where the compact companion has a mass in excess of 3 Mmc060-1.jpg.
e.
pulsars that are orbited by planets.
 

 61. 

Younger stars have more heavy elements because
a.
the heavy elements were made in previous generations of stars.
b.
old stars destroy heavy elements as they age.
c.
young stars burn their nuclear fuels faster.
d.
heavy elements haven't had time to settle to the core of these younger stars.
e.
all of these
 

 62. 

Observations of galaxies and clusters of galaxies indicate that about _________ per cent of the universe is dark matter.
a.
25
b.
75
c.
50
d.
5
e.
95
 

 63. 

None of the pulsars emit pulses of visible light because
a.
the gravitational field of a pulsar is so great that the visible light emitted is red shifted.
b.
A few pulsars do emit visible light pulses.
c.
pulsars contain black holes that won't let visible light escape.
d.
pulsars are to hot to emit visible light.
e.
pulsars are too far away for the visible light to be bright enough to be detected at Earth.
 

 64. 

Sgr A* is believed to be the center of the Milky Way galaxy because

I. It lies in the general direction of the center of the galaxy based on observations of globular clusters.
II. It is located near the galactic corona.
III. It is easily visible with optical telescopes and has the appearance of a massive black hole.
IV. It does not move with respect to the rest of the galaxy.
a.
I & IV
b.
I, III, & IV
c.
II & IV
d.
II & III
e.
I & II
 

 65. 

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
 

 66. 

In degenerate matter
a.
pressure depends only on the temperature.
b.
temperature depends only on density.
c.
pressure does not depend on temperature.
d.
pressure does not depend on density.
e.
b and c
 

 67. 

An isolated black hole in space would be difficult to detect because
a.
there would be very few stars behind it whose light it could block out.
b.
it would be stationary.
c.
there would be no light source nearby.
d.
it would not be rotating rapidly.
e.
very little matter would be falling into it.
 

 68. 

A type-II supernova
a.
occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
b.
is the result of helium flash.
c.
is characterized by a spectrum that shows hydrogen lines.
d.
occurs when the iron core of a massive star collapses.
e.
c and d
 

 69. 

The bottom-up theory states that the galaxy formed
a.
as two massive galaxies collided.
b.
from a large cloud of material that broke off a larger galaxy.
c.
as material accreted around a massive black hole currently at the center of our galaxy.
d.
as a result of mergers between several smaller groups of gas, dust, and stars.
e.
from material that had been ejected in the violent explosion of a dying galaxy.
 

 70. 

As a star exhausts hydrogen in its core, it
a.
it becomes larger in radius and hotter.
b.
becomes cooler and less luminous.
c.
becomes hotter and more luminous.
d.
becomes cooler and more luminous.
e.
becomes hotter and less luminous.
 

Fill In the Blank
Complete each of the folloiwng statements. (5-Points Each)
 

 71. 

The maximum mass of a white dwarf is _________ solar masses.
 

 

 72. 

Electrons moving in a strong magnetic field emit _________ radiation.
 

 

 73. 

Mass can flow from one star in a binary system to its companion through the first _________ point.
 

 

 74. 

A gas in which the pressure no longer depends on the temperature of the gas is said to be _________.
 

 

 75. 

Label each galaxy in the tuning fork diagram below. Record your labels on the lines provided above or below the galaxy.

co075-1.jpg
 

 

 76. 

The _________ of a black hole is the radius from the black hole at which the escape velocity is equal to the speed of light.
 

 

 77. 

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

 

 78. 

The age of a star cluster can be determined from the _________ of the cluster.
 

 

 79. 

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

 

Short Answer
Provide a short answer for the following question. (5-Points or More Each)
 

 80. 

What is the difference between a population I star and a population II star?
 

 81. 

How do theories of the origin of the Milky Way explain its halo?
 

 82. 

Explain how we can find the age of a star cluster.
 

 83. 

What are the four laws of stellar structure discussed in class?

      a._________________________________________________

      b._________________________________________________

      c._________________________________________________

      d._________________________________________________
 

 84. 

Why can't lower main sequence stars become giant stars?
 

 85. 

What observations indicate the presence of dust in the interstellar medium?
 

 86. 

Why do nuclear reactions in a star occur only near its center?
 

 87. 

Why are Cepheid variable stars important in our study of the Milky Way galaxy?
 

 88. 

On the diagram below, draw the evolutionary track of a protostar to the sun, from the main sequence to a white dwarf.. 

a. Label the major stages on this track.
b. Show the time that star spends on each group.
c. Show the loss or gain of any mass during this process.


es088-1.jpg
 

 89. 

How does a gas cloud become hot enough to ignite nuclear reactions?
 

 90. 

Why does the rotation of our galaxy suggest that it is more massive than previously thought?
 

 91. 

Why do we not expect to find a 5 solar mass neutron star?
 

 92. 

What observational evidence do we have that black holes exist?
 

 93. 

If the sun and stars are supported by gas pressure, what supports a neutron star?
 

 94. 

Explain what keeps the nuclear reaction in a star under control.
 

 95. 

What observations confirm the existence of protostars?
 

 96. 

If white dwarfs have exhausted their fuel, why are they hot?
 

 97. 

Name the three methods of energy transfer discussed in class.

      a._________________________________________________

      b._________________________________________________

      c._________________________________________________
 

 98. 

What assumptions do we make when we use the Hubble constant to estimate the distance to a galaxy?
 

 99. 

What are the six distance indicators discussed in class?
 



 
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