Name: 
 

Test 3 - Chapters 09, 10, 11, 12, 13 & 14



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

 1. 

The sun has a core in which energy travels outward primarily by radiation.
 

 2. 

Until recently, most astronomers thought elliptical galaxies were shaped like oblate spheroids.
 

 3. 

The dust in the interstellar medium can make distant stars look redder than they really are.
 

 4. 

The ‘pizza theory’ is used to briefly explain the hailo of the Milky Way galaxy.
 

 5. 

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

 6. 

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

 7. 

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

 8. 

Theory predicts that neutron stars may not exceed 3 solar masses.
 

 9. 

Hydrostatic equilibrium refers to the balance between weight and pressure.
 

 10. 

Hydrostatic equilibrium keeps a star’s nuclear reactions under control.
 

 11. 

Old stars are poor in heavy atoms because there were very few previous generations of stars before the old stars formed.
 

 12. 

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

 13. 

Giant molecular cloud complexes are located in spiral arms.
 

 14. 

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

 15. 

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

 16. 

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

 17. 

Spiral tracers tend to be old, luminous stars.
 

 18. 

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

 19. 

Many pulsars have periods that are gradually increasing as the spinning neutron stars lose energy.
 

 20. 

Stars less massive than 0.4 solar mass never become giant stars.
 

 21. 

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

 22. 

Ninety percent of all stars fuse helium to form carbon and lie on the main sequence.
 

 23. 

When a large galaxy collides with a small galaxy, the smaller galaxy may be pulled apart by tidal forces.
 

 24. 

A nova destroys the star and leaves behind a white dwarf.
 

 25. 

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

 26. 

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

 27. 

The center of our galaxy is believed to be occupied by the radio source known as Sgr A* or Sagittarius A*.
 

 28. 

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

 29. 

We would not expect to find a 5 solar mass neutron star because it would be a black hole.
 

 30. 

Planetary nebulae are sites of planet formation.
 

 31. 

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

 32. 

Electrons moving in a weak magnetic field emit synchrotron radiation.
 

 33. 

The event horizon or Schwarzschild radius of a black hole is the radius from the black hole at which the escape velocity is equal to the speed of light.
 

 34. 

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

 35. 

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

 36. 

Even in degenerate matter, pressure depends on temperature.
 

 37. 

Quasar red shifts are usually larger than the red shifts of the visible galaxies.
 

 38. 

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

 39. 

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

 40. 

The Milky Way galaxy is not a radio galaxy, it emits no radio radiation.
 

 41. 

The sun will eventually become a supernova.
 

 42. 

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

 43. 

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

 44. 

The rotation curve method can be applied only to pairs of galaxies orbiting each other.
 

 45. 

The disk of the galaxy is older than the halo.
 

 46. 

Because of the rapid rotation of the outer portion of our galaxy suggest that it is more massive than we previously thought.
 

 47. 

Some large clusters of galaxies do not appear to contain enough mass to hold themselves together.
 

 48. 

The sun and stars are supported by gas pressure, neutron stars are supported by internuclear forces.
 

 49. 

Cepheid variable stars are more luminous than the sun.
 

 50. 

No known white dwarf has a mass greater than the Chandrasekhar limit.
 

 51. 

The helium flash is the cause of some supernovae.
 

 52. 

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

 53. 

Giant and supergiant stars are rare because that stage of stellar evolution is short.
 

 54. 

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

 55. 

The center of our galaxy shows signs of past eruptions.
 

 56. 

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

 57. 

Elliptical galaxies contain more gas, dust and young stars than do Sa galaxies.
 

 58. 

Helium fusion does not begin until the star has entered the giant region of the H-R diagram.
 

 59. 

If the accretion disk around a black hole emits X rays outside the event horizon, the X rays can escape.
 

 60. 

Neutron stars have densities roughly the same as that of the atomic nucleus.
 

 61. 

The sun and stars are supported by gas pressure, atom-atom repulsion supports white dwarfs.
 

 62. 

We can find the age of a star cluster by determining the turn-off point on the HR diagram.
 

 63. 

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

 64. 

A Type II supernova produces a planetary nebula.
 

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

 65. 

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.
a spherical component
e.
an accretion disk.
 

 66. 

The center of our galaxy lies in the direction of the constellation of
a.
Sagittarius.
b.
Ursa Major.
c.
Orion.
d.
Ursa Minor.
e.
Monoceros.
 

 67. 

The bottom-up theory states that the galaxy formed
a.
from a large cloud of material that broke off a larger galaxy.
b.
as material accreted around a massive black hole currently at the center of our galaxy.
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.
 

 68. 

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

 69. 

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

 70. 

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

 71. 

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 formed by material falling into the galaxy.
c.
they are powered by magnetic fields.
d.
they are excited by radiation from nearby galaxies.
e.
they are created by jets from the galaxy.
 

 72. 

Star cluster are important to our study of stars because
a.
they give us a method to test the our theories and models of stellar evolution.
b.
the sun was once a member of a globular cluster.
c.
they are the only objects that contain Cepheid variables.
d.
all stars formed in star clusters.
e.
all of the above
 

 73. 

The first stars to form in our galaxy
a.
formed the galactic clusters we see today.
b.
had highly elliptical orbits.
c.
were population I stars.
d.
had circular orbits.
e.
all had orbits in the same plane.
 

 74. 

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

 75. 

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

 76. 

Good spiral tracers are all

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

 77. 

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

 78. 

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

 79. 

A pulsar requires that a neutron star

I.
rotate rapidly.
II.
have a radius of at least 10 km.
III.
have a strong magnetic field.
IV.
rotate on an axis that is different from the axis of the magnetic field.
a.
II, III, & IV
b.
I & IV
c.
I, II, III, & IV
d.
I, III, & IV
e.
I & III
 

 80. 

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

 81. 

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

 82. 

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 arms have larger Doppler shifts.
d.
the stars in the spiral arms emit most of their energy at radio wavelengths.
e.
the dust in spiral arms is denser.
 

 83. 

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

 84. 

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

 85. 

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 only two smooth spiral arms.
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.
 

 86. 

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
 

 87. 

If white dwarfs have exhausted their fuel, why are they hot?
a.
The Doppler Effect
b.
Hydrostatic Equilibrium
c.
The Zeeman Effect
d.
Thermal Lag.
 

 88. 

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?

mc088-1.jpg
a.
The absolute magnitude of a Cepheid
variable cannot be determined unless
its distance is known.
b.
-1
c.
0
d.
-6
e.
-4
 

 89. 

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

 90. 

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
 

 91. 

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

 92. 

The age of the Milky Way galaxy has been estimated to be at least 15 billion years based on
a.
the energy produced by Sagittarius A*.
b.
the rotation curve of the galaxy.
c.
observations of globular clusters.
d.
observations of open clusters.
e.
21-cm radiation from H I regions.
 

 93. 

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
 

 94. 

The density of a neutron star is
a.
about the same as an atomic nucleus.
b.
about the same as that of a white dwarf.
c.
smaller than expected because the magnetic field is so strong.
d.
about the same as that of the sun.
e.
about the same as a water molecule.
 

 95. 

Massive stars cannot generate energy through iron fusion because
a.
stars contain very little iron.
b.
no star can get hot enough for iron fusion.
c.
iron is the most tightly bound of all nuclei.
d.
massive stars supernova before they create an iron core.
e.
iron fusion requires very high density.
 

 96. 

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
 

 97. 

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

 98. 

Which of the following is not a characteristic of the stars of the disk component of our galaxy?
a.
star formation regions
b.
circular orbits
c.
randomly inclined orbits
d.
young stars
e.
higher metal abundance
 

 99. 

__________ 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 proton-proton chain
d.
The CNO cycle
 

 100. 

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

 101. 

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

 102. 

_________ 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.
Edwin Hubble
b.
Carl Sagan
c.
John Glenn
d.
Henrietta Leavitt
e.
Annie Cannon
 

 103. 

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

 104. 

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

 105. 

Who first calibrated the Cepheid variable stars for use in determining distance?
a.
Edwin Hubble
b.
John Glenn
c.
Henrietta Leavitt
d.
Harlow Shapley
e.
Carl Sagan
 

 106. 

Stars with masses between 0.4 Mmc106-1.jpg and 4 Mmc106-2.jpg
a.
undergo thermonuclear fusion of hydrogen, but never get hot enough to ignite helium.
b.
undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to ignite carbon.
c.
produce type-I supernovae after they exhaust their nuclear fuels.
d.
produce type-II supernovae after they exhaust their nuclear fuels.
e.
undergo carbon detonation.
 

 107. 

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

 108. 

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

 109. 

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

 110. 

Why do nuclear reactions in a star occur only near its center?
a.
This is where the highest pressure is.
b.
This is where the greatest temperature is.
c.
All of the above.
d.
None of the above.
 

 111. 

The rotation curve of a galaxy can be used to determine
a.
the mass of the galaxy.
b.
the luminosity 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 radius of the galaxy.
 

 112. 

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.
white dwarf black hole
e.
pulsar white dwarf
 

 113. 

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

 114. 

Population II stars

I.
are primarily found in the disk of the galaxy.
II.
contain more heavy metals than population I stars.
III.
are primarily old low mass stars.
IV.
are located in globular clusters.
a.
III & IV
b.
I & II
c.
I, II, & III
d.
II
e.
IV
 

 115. 

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

 116. 

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

 117. 

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
 

 118. 

The search for black holes involves searching for
a.
pulsars that are orbited by planets.
b.
large spherical regions from which no light is detected.
c.
single stars that emit large amounts of x-rays.
d.
x-ray binaries where the compact companion has a mass in excess of 3 Mmc118-1.jpg.
e.
pulsars with periods less than one millisecond.
 

 119. 

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
 

 120. 

Why are Cepheid variable stars important in our study of the Milky Way galaxy?
a.
It helps us understand the shape of our galaxy.
b.
It helps us understand the size of our galaxy.
c.
It allows us to determine the center of our galaxy.
d.
All of the above
e.
None of the above
 

 121. 

What causes the outward pressure that balances the inward pull of gravity in a star?
a.
The density of the gas
b.
The opacity of the gas.
c.
The outward flow of energy.
d.
c and d
e.
The temperature of the gas.
 

 122. 

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

 123. 

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
 

 124. 

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

 125. 

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 nova explosion.
e.
produced by a supernova explosion.
 

 126. 

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
 

Fill In The Blank
Complete each statement.
 

 127. 

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

co127-1.jpg
 

 

Short Answer
Provide a short answer for each of the following questions.
 

 128. 

If neutron stars contain no nuclear fuel, why are they hot?
 

 129. 

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.


es129-1.jpg
 

 130. 

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

 131. 

Explain why good distance indicators must be luminous objects.
Why must they be unambiguously recognizable?
 

 132. 

Name the three methods of energy transfer discussed in class.

      a._________________________________________________

      b._________________________________________________

      c._________________________________________________
 

 133. 

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.


es133-1.jpg
 

 134. 

What are the six distance indicators discussed in class?
 



 
Check Your Work     Start Over