1. Which has a higher intensity viewed from 1 m away?
A household 100 W light bulb
A 100 W fluorescent overhead tube
They will have the same intensity

2. Star G has an apparent magnitude of +5
Star G has an apparent magnitude of +5.0 and an absolute magnitude of Star H has an apparent magnitude of +4.0 and an absolute magnitude of Which star appears brighter in the night sky?
Star G
Star H
They will appear the same

3. Altair’s apparent magnitude is +0. 77 and its absolute magnitude is +2
Altair’s apparent magnitude is and its absolute magnitude is How far is Altair from Earth?
Less than 10 parsecs
10 parsecs
More than 10 parsecs

4. Which of the following is correct?
Apparent magnitude is a measure of intensity
Absolute magnitude is a measure of flux
Apparent magnitude is a measure of luminosity
Absolute magnitude is a measure of luminosity

5. This graph shows the blackbody spectra of three stars
This graph shows the blackbody spectra of three stars. Which has the highest surface temperature?
Antares
Spica
The Sun

6. The surface of Rigel is four times as hot as Betelgeuse, and its diameter is 16 times smaller than Betelgeuse. Rigel is a bit further away from us than Betelgeuse.
Rigel is 16 times less luminous than Betelgeuse
Rigel is 16 times more luminous than Betelgeuse
The stars have the same luminosity
You need their exact distances to determine their relative luminosities

7. The star Aldebaran is 10 times closer than Betelgeuse and has roughly the same surface temperature. Using this picture which shows their intrinsic sizes, which of the following is approximately true?
We receive 9 times more flux from Aldebaran
We receive 9 times less flux from Aldebaran
The stars have about the same flux
40 Rsun
1200 Rsun

8. Alpha Centauri has about the same radius and surface temperature as our Sun, and is about 1.33 pc from Earth. It has apparent magnitude zero, while our sun has apparent magnitude -27.
The luminosity of α Cen is larger than our Sun
The luminosity of α Cen is much less than our Sun
The flux from α Cen is about 1010 times less than our Sun
The absolute magnitude of α Cen is much smaller than our Sun

9. Spectrum A Spectrum B Spectrum C None of these
A thin, cold gas cloud lies between you and a bright blackbody. Which of these spectra would you expect to see when you look toward the blackbody?
Spectrum A
Spectrum B
Spectrum C
None of these

10. Astronomers determine the “color” of a star by calculating the
ratio of fluxes as measured with two different filters
difference between the fluxes as measured with two different filters
ratio of the absolute and the apparent brightness
difference of the absolute and the apparent brightness
Does Betelgeuse look reddish to you? Go outside tonight and see!

11. The main reason that flux measurements with filters gives temperatures of stars is
Hotter stars lie further away from us
More luminous stars lie further away from us
If you compare any two stars, the colder one is always less luminous
The light from colder stars always peaks at lower frequency

12. Two stars are in a binary system and are separated by 200 A. U
Two stars are in a binary system and are separated by 200 A.U. Star 1 is 5 solar masses. Star 2 is 2 solar masses. The period of star 1 around the center of mass is ______ the period for star 2 around the center of mass.
larger than
smaller than
the same as
not enough info
given to answer this

13. The spectrum of Sirius A peaks at 5. 8 x 1014 Hz
The spectrum of Sirius A peaks at 5.8 x 1014 Hz. The spectrum of Sirius B peaks at 1.5 x 1015 Hz. From this information alone, you can deduce that
Sirius A is smaller than Sirius B
Sirius A is less luminous than Sirius B
Both of the above are true
You can’t deduce any of the above

14. In a binary star system, star A is twice as massive as star B
In a binary star system, star A is twice as massive as star B. The orbital plane is at an inclination of 45°. Which of the following is always true?
Star A will experience larger blue shifts than B
Star A will experience smaller blue shifts than B
The orbital period of star A is larger than star B
The orbital period of star A is smaller than star B

15. For stars larger than the Sun, luminosity goes as (mass)4 , while radius goes as (mass)0.5. If every star uses up the same fraction of its mass over its lifetime, then you would expect that:
High mass stars live longer
Low mass stars live longer
High and low mass stars live to about the same age
More luminous stars live longer

16. In space you come across some neutral 3H
In space you come across some neutral 3H. Your ship’s sensors tell you that it has
1 neutron, 1 proton and 1 electron
1 neutron, 1 proton, and 2 electrons
1 neutron, 2 protons, and 2 electrons
2 neutrons, 1 proton, and 1 electron

17. An interstellar cloud is made up of a neutral gas that is 25% Hydrogen by mass and 75% Helium by mass. Its mean molecular mass is:
13/4
7/16
16/7
4/13

18. If you fully ionize an initially pure Helium gas, its mean molecular mass will:
Decrease by a factor of 3
Increase by a factor of 3
Increase by a factor of 4
Decrease by a factor of 4

19. Our Sun doesn’t collapse under its own gravity because:
Its atoms are packed extremely tightly together
Its hot gas exerts pressure
Its atoms electromagnetically repel each other
It produces huge numbers of photons in its core

20. Given what you know about surface gravity and mass-radius relations for main sequence stars at least 1.66 times as massive as our Sun:
The surface gravity varies very little with mass
More massive stars have much higher surface gravity
Less massive stars have much higher surface gravity

21. Which class of main sequence star has the longest lifetime?
Class A
Class M
Class O
These all have about the same lifetime

22. The luminosity classes of main sequence stars:
depend on both radius and temperature
depend solely on mass
depend solely on luminosity
are all about the same as our Sun’s

23. Using the spectroscopic parallax method, you measure a star to be 76 pc away. You now find out that the star is actually luminosity class I instead of class V. That makes your original distance measurement
Too large
Too small
Correct – no change to your estimate is needed

24. The spectral class of a star depends solely on
temperature
mass
luminosity
radius

25. (Optical) Deep Thoughts:
If the Sun is a giant ball of gas whose pressure drops off as -dP/dr, and photons are produced only in a small region in its center, then why does it look like a circular disk?

26. Which of the following has an optical depth much smaller than 1?
Your textbook in visible light
Our atmosphere in gamma-rays
The walls of this classroom in radio waves
A mirror in visible light

27. If there is such a steep temperature gradient inside the Sun, then why does its spectrum look like a blackbody?

28. The mean free path can be described as:
Inversely proportional to opacity and density
The average distance travelled by a particle between collisions
The distance over which the optical depth grows from zero to one
All of the above

29. Much longer than a solar radius Much smaller than a solar radius
You might expect the mean free path of a photon that starts out deep inside the Sun to be
Much longer than a solar radius
Much smaller than a solar radius
About equal to a solar radius
About equal to one astronomical unit

30. If you were to suddenly crank up the energy generation rate at the center of the Sun, the inner regions of the Sun would
Be more likely to transfer heat via convection
Remain unchanged
Be more likely to transfer heat via radiation
Be more likely to transfer heat via conduction

31. Increasing the opacity 𝜅 of a gas layer within a star will tend to
make the layer less likely to be convective
flatten the temperature gradient
steepen the temperature gradient
have no other effect on the layer

32. Some helium atoms have less than 2 protons
Consider the following mass comparisons (in atomic mass units):
Proton mass = Hydrogen atom mass =
Neutron mass = Helium atom mass =
Why does helium (2 protons + 2 neutrons) have a mass less than 4?
Some helium atoms have less than 2 protons
The mass is lost when two protons are converted to two neutrons
It takes energy to pull a helium nucleus apart
Helium atoms move so fast that they have a lower apparent mass

33. In general, fusion is most likely to occur between two particles with
High relative velocity
High electric charge with the same sign
High masses
High magnetic charge

34. The Sun’s corona has temperatures roughly as hot as the Sun’s core
The Sun’s corona has temperatures roughly as hot as the Sun’s core. So why doesn’t fusion occur in the corona?
The gas density is too low
The gas is fully ionized
The gas is only 70% hydrogen
All of the above

35. About 25% of the mass of a newborn star is helium
About 25% of the mass of a newborn star is helium. Why doesn’t it fuse while the star is on the main sequence?
Helium fusion requires three nuclei to interact within a very short amount of time
For a given gas temperature, helium nuclei move slower than hydrogen nuclei
Helium nuclei repel each other more strongly than hydrogen nuclei
All of the above

36. The energy from fusion reactions that goes into neutrinos doesn’t heat up the Sun because neutrinos
are massless and thus carry no energy
have no electric charge
have a very large mean free path
rapidly decay

37. A star remains at constant size and temperature for a long period of time. Which of the following is mostly likely to be true? The star generates
about as much energy as it radiates
more energy than it radiates into space
less energy than it radiates into space

38. When starlight passes through interstellar dust
The wavelengths all get longer (redder)
It gets fainter
The red light tends to scatter sideways while the blue continues to us
All of the above

39. An interstellar dust cloud drifts in front of a star
An interstellar dust cloud drifts in front of a star. In terms of numerical values for color index and apparent magnitude, its observed
(B – V) is larger, and mV is smaller
(B – V) is larger, and mV is larger
(B – V) is smaller, and mV is smaller
(B – V) is smaller, and mV is larger

40. In terms of mass, the largest component of the interstellar medium is
Helium gas
Dust
Hydrogen gas
Planets

41. Hot emission nebulae are somewhat red, and cool reflection nebulae are blue. Why are these colors different from what Wien's law tells us about the radiation emitted by a blackbody?
The regions producing light in emission nebulae are optically thick
The dust grains in reflection nebulae scatter longer wavelengths of visible light better than shorter wavelengths.
The light we see from emission nebulae has been strongly absorbed by dust
None of the above

42. Which of these would have the largest diameter H II region?
O3 V star surrounded by a hydrogen cloud with a low free electron density
G2 V star surrounded a hydrogen cloud with a low free electron density
G2 V star surrounded a hydrogen cloud with a high free electron density
O3 V star surrounded by a hydrogen cloud with a high free electron density

43. If a free electron encounters a magnetic field it will
Accelerate away from it and emit nothing
Ignore it
Accelerate toward it and emit radiation
Annihilate and produce a gamma-ray

44. As you increase the eccentricity of an orbit, it becomes more elliptical, and the focus
Moves towards the center of the ellipse
Stays put
Moves towards the edge of the ellipse
Moves to a point outside the ellipse

45. If you perturb the edge of a molecular cloud, the perturbation will travel through the cloud
on the free-fall timescale
at the speed of light
at the speed of sound
on the thermal timescale

46. If the material in the primordial Solar System retained its angular momentum as it collapsed to form the Sun, the Sun’s current rotation rate should be
Slow (more than a month period)
Fast (less than a week period)
Moderate (week to a month period)
Zero (non-rotating)

47. According to the Virial theorem, if you compress a ball of gas in hydrostatic equilibrium:
The temperature of the gas will remain the same
The temperature of the gas will increase
The temperature of the gas will decrease

48. For our Sun, which is longest – the thermal timescale (GM2/LR) , the free-fall timescale (R3/GM) , or the nuclear timescale (2 Myr x M/L) ? note: 1 year ≈ π x 107 sec.
nuclear
thermal
free-fall
all three are roughly the same

49. If the charge on the proton were increased, then the masses of the lowest mass stars on the main sequence would be
unchanged
smaller
larger

50. The low number density of the particles
The main source of pressure in a degenerate gas is
The low number density of the particles
The high kinetic energies of the particles
The filling up of available energy states
Degenerate gasses do not supply pressure

51. In a fully degenerate gas, the pressure is dependent on:
The density and temperature
The temperature only
The density only

52. Which is the oldest open cluster here?
NGC 188
NGC 2362
h + χ Persei
All are about the same age

53. Our Sun doesn’t pulsate because
Its oscillations aren’t driven at the right period
There is no companion star to perturb it
It is no longer on the main sequence
Its outermost layer is convective

54. White dwarfs support themselves against gravitational collapse by
Coulomb pressure
Helium gas pressure
Carbon gas pressure
Electron degeneracy pressure

55. Which is ranked correctly from least dense to most dense?
Black hole, white dwarf, neutron star
Neutron star, black hole, white dwarf
White dwarf, neutron star, black hole
All of three have about the same density

56. If were to drop your pen from 1 m high on the surface of a 1 solar mass neutron star, it will hit the surface at
104 m/s
10 m/s
100 m/s
106 m/s

57. Our Sun will end up as
A white dwarf
A black hole
A neutron star
A supernova remnant

58. The mechanism that makes a white dwarf shine is
Fusion of material dumped on its surface
Gravitational contraction
Nuclear fusion in the core region
Escape of heat left over from its formation

59. In order for a white dwarf to become a nova it must
Have had a main sequence mass > 7 Msun
Be heavier than 1.44 solar masses
Have a companion star
Continue fusing elements up to iron

60. It is much more difficult to escape the surface of a neutron star compared to a normal star because
It is much hotter
It is much heavier
It is much denser
It has much lower surface radiation pressure

61. If a pulsar rotates 1000 times per second, special relativity and classical mechanics imply that compared to a normal star it must be
Much larger and less dense
Much larger and denser
Much smaller and denser
Much smaller and less dense

62. A supernova is
Something our Sun will eventually do
The eventual fate of a very high mass star
A really bright nova event
The creation of a very high mass star

63. The event horizon of a 1. 0 Msun black hole is 3 km
The event horizon of a 1.0 Msun black hole is 3 km. Thus, the event horizon for a 2 solar mass black hole must be
3.0 km
0.75 km
1.5 km
6 km

64. If our Sun were to suddenly replaced by a 1 Msun black hole, the Earth would
Start to fly outward at a tangent to its orbit
Start to spiral inward toward the black hole
Stay in its current orbit
Start to fly outward in a direction opposite to the black hole

65. An astronaut falling into a black hole would be ‘spaghettified’ by
Magnetic forces: the black hole’s powerful magnetic field pulls her apart
Tidal forces: gravity pulls her feet much stronger than her head
Centripetal forces: the rapid rotation of the event horizon stretches her out

66. Black holes are black because
They are extremely cold
They are blackbodies
Their escape velocity exceeds light speed
They are theoretical objects that have never been seen

67. In a supernova or gamma-ray burst, what type of energy is converted to radiation?
Electromagnetic
Thermonuclear fusion
Neutron degeneracy
Gravitational

68. Considerably fainter than the Sun Considerably brighter than the Sun
If a 1045 W gamma-ray burst exploded at the distance of Alpha Centauri (1 pc), it would appear: (hint: 1 pc roughly 200,000 AU)
Considerably fainter than the Sun
Considerably brighter than the Sun
About the same brightness as the Sun

69. The mass interior to the star’s orbit The mass of the star
The radius of a star’s orbit and its velocity – the data implied by a star’s location on a rotation curve – can be used to determine
The mass interior to the star’s orbit
The mass of the star
The mass of the entire galaxy
The mass at the center of the galaxy

70. Red Blue Green None of these
Which curve represents the trend of velocity versus radius for a solid rotating disk?
Red
Blue
Green
None of these

71. Disk , low metallicity gas Halo , high density gas Bulge , supernovae
Young stars are predominantly found in the ___ of our galaxy since _____ there causes stars to form.
Disk , a density wave
Disk , low metallicity gas
Halo , high density gas
Bulge , supernovae

72. (A)
(B)
(C)
(D)

73. How astronomers classify galaxies
Edwin Hubble’s ‘tuning fork’ diagram describes
How astronomers classify galaxies
Different possible models for our Milky Way
How galaxies evolve, from left to right
How Ed Hubble liked his lattes prepared

74. Optical telescopes currently aren’t large enough
Optical telescopes can’t give us a good view of the galactic center because
Optical telescopes currently aren’t large enough
There is too much dust in the way
The galactic center is too far away
Our atmosphere distorts the images too much

75. Which observation would provide the best evidence that the disk of the Milky Way does NOT rotate like a solid wheel?
Disk stars twice as far from the galactic center rotate twice as fast around it
Disk stars have Doppler shifts
The brightest disk stars form spiral arms
The rotation of the disk stars near the Sun decreases with distance according to Kepler’s laws

76. About the same age as we previously thought
The currently accepted value for the Hubble constant is about 70 km/s/Mpc. If we were to suddenly discover it was actually 200 km/s/Mpc, the age of the universe would then be
About the same age as we previously thought
Much older than we previously thought
Much younger than we previously thought

77. Consider three widely separated galaxies in an expanding universe
Consider three widely separated galaxies in an expanding universe. Imagine you are located in galaxy A and have observed that both galaxies B and C are moving away from you. What would someone in galaxy C say about the motion of B? A B C
It is moving away from them
It is not moving
It is moving toward them

78. Doppler shift of its spectral lines
Say you want to measure the distance to the closest galaxy (Andromeda). The best method to use is
Doppler shift of its spectral lines
Period-luminosity relation for Cepheid stars
The Hubble law of recession for galaxies
Trigonometric parallax using Earth’s orbit

79. In the radio galaxy M87, you can only see one jet because
Light from the other jet is beamed away from us
Dust is obscuring the other jet
Only one jet is currently being produced
The other jet is so far away its light hasn’t reached us yet

80. The large Doppler velocity widths of broad emission lines in active galaxies could NOT be created by hot emitting clouds that are
Being ejected along a narrow-angled jet
Swirling at high velocities around a black hole
Falling into the neighborhood of a black hole

81. The most distant quasar at z = 7
The most distant quasar at z = 7.1 has an apparent optical magnitude of 21. How much fainter is it than the faintest star you can detect with your naked eye (magnitude = 6) ?
100 x
1000 x
1,000,000 x
1,000,000,000 x

82. You detect a narrow width Lyman α absorption line in the spectrum of a quasar which is at a significantly shorter wavelength than the quasar’s observed Lyman α emission line. You conclude that the absorbing cloud is
Warm and located close to the quasar
Cold and located close to the quasar
Cold and located close to the Milky Way
Warm and located close to the Milky Way

83. At high redshift, a larger fraction of galaxies are “active” than at low redshift. From this, we can safely conclude that
All galaxies may become active more than once in their lifetime
All galaxies go through an active phase, and fewer galaxies in the past were active than now
Some galaxies go through an active phase, and more galaxies in the past were active than now
Most galaxies never become active in their lifetime

84. Which cluster is the most likely to be relaxed?
Cluster A
Cluster B

85. Gravitational lenses are often detected at optical wavelengths because
Dark matter absorbs light at all other wavelengths
Gravity bends spacetime only for optical wavelengths
There is typically less obscuration in the optical
Distant background galaxies emit most of their light in the optical

86. When Andromeda and our Milky Way merge,
Very few of the stars in either galaxy will survive
The dark matter halos will annihilate each other in a giant explosion
A new elliptical galaxy will eventually form
The two galaxies will annihilate each other, since Andromeda is made of antimatter

87. Which of the following measurements can NOT be used to measure the amount of dark matter in a galaxy cluster?
The deflection of light rays from a background object passing by the outskirts of the cluster
The average speed of galaxies orbiting the cluster center
The dispersion in the speeds of the galaxies orbiting the cluster center
The properties of X-rays emitted by gas that has been heated by falling into the cluster

88. The night sky is relatively dark because the Universe
is very large
is filled with light-absorbing dust
is mostly empty
has a finite age

89. Olber’s Paradox asks why the night sky is dark, when every line of sight must eventually fall on a star. It is dark primarily because the Universe is
Expanding, so that distant stars are redshifted
Infinite and mostly empty
Young, so there are only stars out to a finite distance
Clumpy, so that not every sightline hits a star

90. The near-perfect blackbody spectrum of the cosmic microwave background implies that at one time,
the Universe was very much like a giant black hole
the Universe was optically thick
the mean free path of photons in the Universe was very long
the Universe was much colder than it is now

91. The cosmic background radiation is visible in every direction since
We are looking back to when the Universe was cold
We are at the center of the Universe
We are looking back to when the Universe was young in every direction
It has scattered in every direction over the age of the Universe

92. Dark matter has so far not been detected in the lab most likely because
Radiation pressure from our Sun pushes it outward
Dark matter is only found in distant galaxies
It rarely interacts with normal matter
It has a very short decay half life

93. The observed redshifts of galaxies mean that
Photons lose energy as they travel through space
We are the center of an expanding Universe
Gravity can never overcome the expansion left over from the Big Bang
Galaxies were moving much faster with respect to each other when the Universe was very young

94. The consensus model of cosmology indicates
The expansion of the Universe has stopped
The expansion of the Universe is slowing
The expansion of the Universe is accelerating
The Universe is currently contracting

95. The lookback time to an object is the # of years between when the object emitted its light and when we see it. What piece of information surely does NOT affect the lookback time for a distant object?
The rate of expansion of the Universe
Its distance
The speed of light
The wavelength of light being observed

96. As the Universe evolves over time
The energy density of dark energy remains constant
The energy density of dark matter increases
The energy density of dark energy increases
The energy density of dark matter remains constant

97. Since the time when the cosmic microwave background was created, the Universe has expanded by approximately a factor of 10
1000
100000
10 million

98. The luminosity distance is defined as the distance over which
The universe has expanded in the time the light from the object takes to reach us
The small angle formula applies
The comoving coordinates stay constant
The inverse square law of light applies

99. By observing the cosmic microwave background, the Planck mission confirmed that on the whole, spacetime in the Universe is
Positively curved, like a sphere
Negatively curved, like a saddle
Flat

100. Which product name isn’t associated with an astronomical phenomenon?
Starburst
Nova
Pulsar
Quark
Quark