Name: 
 

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



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

 1. 

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

 2. 

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

 3. 

The sun will eventually become a supernova.
 

 4. 

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

 5. 

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

 6. 

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

 7. 

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

 8. 

Giant molecular cloud complexes are located in spiral arms.
 

 9. 

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

 10. 

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

 11. 

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

 12. 

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

 13. 

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

 14. 

Hydrostatic equilibrium refers to the balance between weight and pressure.
 

 15. 

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

 16. 

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

 17. 

Spiral tracers tend to be old, luminous stars.
 

 18. 

Cepheid variable stars are more luminous than the sun.
 

 19. 

The disk of the galaxy is older than the halo.
 

 20. 

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

 21. 

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

 22. 

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

 23. 

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

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

 24. 

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

 25. 

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

 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.
I & III
c.
I
d.
II & IV
e.
IV
 

 27. 

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 is degenerate when helium ignites.
d.
it is a supergiant.
e.
its core contains oxygen and helium.
 

 28. 

Nucleosynthesis
a.
is the process by which hydrogen and helium are converted into heavier elements.
b.
is the process by which energy is produced at the center of the galaxy.
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.
 

 29. 

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 faster than expected in its inner region.
c.
rotates more slowly than expected in its inner region.
d.
rotates more slowly than expected in its outer region.
e.
rotates faster than expected in its outer region.
 

 30. 

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

 31. 

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

 32. 

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

 33. 

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

 34. 

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

 35. 

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

 36. 

The search for black holes involves searching for
a.
x-ray binaries where the compact companion has a mass in excess of 3 Mmc036-1.jpg.
b.
large spherical regions from which no light is detected.
c.
pulsars with periods less than one millisecond.
d.
pulsars that are orbited by planets.
e.
single stars that emit large amounts of x-rays.
 

 37. 

The chemical abundance of 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.
depends on the temperature of the star.
d.
depends on the mass of the star.
e.
indicates that they contain very few heavy metals compared to halo stars.
 

 38. 

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

 39. 

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

 40. 

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

 41. 

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

 42. 

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

 43. 

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

 44. 

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

 45. 

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

 46. 

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

 47. 

A type-II supernova
a.
is the result of helium flash.
b.
occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
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
 

 48. 

__________ 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
 

 49. 

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

 50. 

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

 51. 

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

 52. 

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.
II & III
b.
I, III, & IV
c.
I & II
d.
I & IV
e.
II & IV
 

 53. 

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
 

 54. 

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

 55. 

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

 56. 

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.
Quasars emitted radio energy like active galaxies, but appeared to be point sources at visible light.
d.
The spectra of quasars looked like that of an M dwarf.
e.
Quasars showed significant gravitational lens effects.
 

 57. 

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

 58. 

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

 59. 

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

 60. 

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

 61. 

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
 

 62. 

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
 

 63. 

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
 

 64. 

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

 65. 

_________ 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.
Edwin Hubble
d.
John Glenn
e.
Henrietta Leavitt
 

 66. 

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

 67. 

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
 

 68. 

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

 69. 

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

 70. 

Good spiral tracers are all

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

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

 71. 

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

 

 72. 

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

 

 73. 

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

co073-1.jpg
 

 

 74. 

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

 

 75. 

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

 

 76. 

Electrons moving in a strong magnetic field emit _________ radiation.
 

 

 77. 

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

 

 78. 

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

 

 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. 

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

 81. 

Name the three methods of energy transfer discussed in class.

      a._________________________________________________

      b._________________________________________________

      c._________________________________________________
 

 82. 

What are the six distance indicators discussed in class?
 

 83. 

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

 84. 

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

 85. 

What observational evidence do we have that black holes exist?
 

 86. 

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

 87. 

What observations confirm the existence of protostars?
 

 88. 

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

      a._________________________________________________

      b._________________________________________________

      c._________________________________________________

      d._________________________________________________
 

 89. 

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

 90. 

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

 91. 

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

 92. 

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

 93. 

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

 94. 

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

 95. 

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.


es095-1.jpg
 

 96. 

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

 97. 

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

 98. 

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

 99. 

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



 
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