Download Practice Questions for Exam 3

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1.
Which of the following statements about thermal radiation is always true?
A. A hot object produces more total infrared emission than a cooler object.
B. A hot object emits more radiation per unit surface area than a cool object.
C. All the light emitted by hot object has higher energy than the light emitted by a cooler
object.
D. A cold object produces more total infrared and radio emission per unit surface area than a
hot object.
2.
Betelgeuse is the bright red star representing the left shoulder of the constellation Orion.
All the following statements about Betelgeuse are true. Which one can you infer from its red
color?
A. It is moving away from us.
B. It is much brighter than the Sun.
C. Its surface is cooler than the surface of the Sun.
D. It is much more massive than the Sun.
3.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than
Star Y. What can you conclude?
A. Star X is coming toward us faster than Star Y.
B. Star X is moving away from us faster than Star Y.
C. Star Y is moving away from us faster than Star X.
D. Star X is moving away from us and Star Y is moving toward us.
4.
Suppose you want to know the chemical composition of a distant star. Which piece of
information is most useful to you?
A. The Doppler shift of the star's spectrum
B. Whether the star's spectrum has more emission lines or more absorption lines
C. The peak energy of the star's thermal radiation
D. The wavelengths of spectral lines in the star's spectrum
5.
Which of the following is the best answer to the question "Why does the Sun shine?"
A. As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly
became stronger and stronger, until the Sun reached its current luminosity.
B. The Sun initially began making energy through chemical reactions. These heated the interior
enough to allow gravitational contraction and nuclear fusion to occur.
C. The Sun initially began generating energy through nuclear fusion as it formed, but today it
generates energy primarily through the sunspot cycle.
D. As the Sun was forming, gravitational contraction increased the Sun's temperature until the
core become hot enough for nuclear fusion, which ever since has generated the heat that
makes the Sun shine.
6.
A.
B.
C.
D.
The Sun's surface, as we see it with our eyes, is called the _________.
photosphere
core
corona
chromosphere
7.
What happens to energy in the Sun's convection zone?
A. Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
B. Energy slowly leaks outward through the radiative diffusion of photons that repeatedly
bounce off ions and electrons.
C. Energy is produced in the convection zone by thermal radiation.
D. Energy is produced in the convection zone by nuclear fusion.
8.
What is the solar wind?
A. It is the wind that causes huge arcs of gas to rise above the Sun's surface, sometimes staying
aloft for weeks.
B. It is the name we give to the gas (or plasma) particles flowing outward from the surface of
the Sun into the solar system.
C. It is the strong winds that blow across the surface of the Sun, causing sunspots to move
around randomly.
D. It is the uppermost layer of the Sun, lying just above the corona.
9.
A.
B.
C.
D.
What do sunspots, solar prominences, and solar flares all have in common?
They all have about the same temperature.
They are all strongly influenced by magnetic fields on the Sun.
They are all shaped by the solar wind.
They all occur only in the Sun's photosphere.
10 .
According to the inverse square law of light, how will the apparent brightness of an
object change if its distance to us doubles?
A. Its apparent brightness will increase by a factor of 4.
B. Its apparent brightness will decrease by a factor of 4.
C. Its apparent brightness will decrease by a factor of 2.
D. Its apparent brightness will increase by a factor of 2.
11 .
Assuming that we can always measure the apparent brightness of a star, what does the
inverse square law for light allow us to do?
A. It allows us to calculate a star's luminosity if we know its distance, or calculate its distance
if we know its luminosity.
B. It allows us to calculate a star's surface temperature if we know either its luminosity or its
distance.
C. It allows us to determine the distance to a star from its apparent brightness.
D. It allows us to determine both distance and luminosity from the apparent brightness.
12 .
A.
B.
C.
D.
If star A is closer to us than star B, then Star A's parallax angle is _________.
hotter than that of Star B
fewer parsecs than that of Star B
larger than that of Star B
smaller than that of Star B
13 .
From hottest to coolest, the order of the spectral types of stars is _________.
A. ABCDEFG
B. OBAGFKM
C. ABFGKMO
D. OBAFGKM
14 .
A.
B.
C.
D.
On an H-R diagram, stellar radii _________.
are greatest in the lower left and least in the upper right
are impossible to determine
increase diagonally from the lower left to the upper right
decrease from left to right
15 .
On an H-R diagram, stellar masses _________.
A. can be determined from a star's position in the diagram only for main sequence stars, and
decrease from upper left to lower right
B. are greatest in the lower left and least in the upper right
C. are impossible to determine
D. decrease from left to right
16 .
You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R
diagram. You will need to determine all of the following, except the _________.
A. distance to the star
B. spectral type of the star
C. apparent brightness of the star in our sky
D. mass of the star
17 .
The choices below each describe the appearance of an H-R diagram for a different star
cluster. Which cluster is most likely to be located in the halo of our galaxy?
A. The diagram shows main-sequence stars of all the spectral types except O and B, along with
a few giants and supergiants.
B. The diagram shows no main-sequence stars at all, but it has numerous supergiants and white
dwarfs.
C. The diagram shows main-sequence stars of spectral types G, K, and M, along with
numerous giants and white dwarfs.
D. The diagram shows main-sequence stars of every spectral type except O, along with a few
giants and supergiants.
18 .
A.
B.
C.
D.
When a main-sequence star exhausts its core hydrogen fuel supply _________.
the entire star shrinks in size
the core immediately begins to fuse its helium into carbon
the star becomes a neutron star
the core shrinks while the rest of the star expands
19 .
The main source of energy for a star as it grows in size to become a red giant is
_________.
A. hydrogen fusion in the core
B. gravitational contraction
C. helium fusion in the core
D. hydrogen fusion in a shell surrounding the central core
20 .
What is a planetary nebula?
A. Gas ejected from a low-mass star in the final stage of its life
B. Gas created from the remains of planets that once orbited a dead star
C. Interstellar gas from which planets are likely to form in the not-too-distant future
D. The remains of a high-mass star that has exploded
21 .
A.
B.
C.
D.
The ultimate fate of our Sun is to _________.
become a rapidly spinning neutron star
become a white dwarf that will slowly cool with time
become a black hole
explode in a supernova
22 .
Why is iron significant to understanding how a supernova occurs?
A. Iron cannot release energy either by fission or fusion, so a star with an iron core has no way
to generate additional energy to counteract the crush of gravity.
B. The fusion of iron into uranium is the reaction that drives a supernova explosion.
C. Iron is the heaviest of all atomic nuclei, and thus no heavier elements can be made.
D. Supernovae often leave behind neutron stars, which are made mostly of iron.
23 .
A.
B.
C.
D.
Which event marks the beginning of a supernova?
The onset of helium burning after a helium flash
The sudden initiation of the CNO cycle
The sudden collapse of an iron core into a compact ball of neutrons
The beginning of neon burning in an extremely massive star
24 .
A.
B.
C.
D.
After a supernova explosion, the remains of the stellar core _________.
may be either a neutron star or a black hole
will always be a neutron star
will always be a black hole
may be either a white dwarf, neutron star, or black hole