ast201h-m16
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Course
201
Subject
Astronomy
Date
Dec 6, 2023
Type
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16
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UNIVERSITY OF TORONTO
Faculty of Arts and Science
APRIL 2016 EXAMINATIONS
AST201H1S
Duration - 3 hours
No Aids Allowed
FIRST NAME:
LAST NAME:
STUDENT NUMBER:
UTORID: (e.g.smitha4)
Instructions:
1.
ON THIS PAGE: Fill in your identifying information above. Make sure you fill in your name
AS IT APPEARS ON ROSI.
2.
ON THE BUBBLE SHEET: Fill in your last name, first initial, and student number in the
spaces given and, using pencil, darkly shade in the corresponding bubbles. Then sign the card.
There is no form code.
3.
For multiple choice questions, mark all answers on the bubble sheet by darkly shading the
appropriate bubbles.
Only answers on the bubble sheet will count for marks.
4.
Answer short answer questions in the spaces provided.
5.
Make sure that your exam paper has 15 pages.
6. This exam is out of 70 marks.
PAGE 1 OF 15
AST201H1S FINAL EXAM, APRIL 2016
PART A: fl mark each] For each question, choose the MOST CORRECT answer and
TRANSFER YOUR ANSWERS TO THE BUBBLE SHEET WHEN YOU ARE DONE.
1.
A Hertzsprung-Russell diagram is a graph that compares which two properties of stars?
a) Mass versus chemical composition
b) Mass versus surface temperature
c) Chemical composition versus luminosity
d) Surface temperature versus luminosity
e)
Surface temperature versus chemical composition
2.
Which of the following is a
FALSE
statement about a 2 solar-mass star on the main sequence?
a)
Its time on the main sequence is the longest phase of this star
5
s life
b) This star's core is supported by electron degeneracy pressure
c)
This star is fusing hydrogen in its core
d) This star is mainly composed of hydrogen and helium
e)
Forces due to gravity and pressure are in balance in this star
3.
On the main sequence, why do low-mass stars show more absorption lines in their spectra than
high-mass stars?
a) Low-mass stars are hotter than high-mass stars
b)
Low-mass stars contain more molecules in their outer layers than high-mass stars
c) Low-mass stars are redder than high-mass stars
d)
Low-mass stars are fusing hydrogen, while high-mass stars are fusing helium
e) Low-mass stars are older than high-mass stars
4.
What are TWO differences between an F star and a K star?
a)
An F star is always hotter, and a K star is always older
b)
An F star is always larger, and a K star is always redder
c)
An F star is always smaller, and a K star is always bluer
d)
An F star is always more luminous, and a K star is always cooler
e)
An F star is always hotter, and a K star is always redder
5.
When the Sun leaves the main sequence, what will happen to its outer layers?
a) They will expand and cool down
b) They will expand and heat up
c) They will shrink and cool down
d) They will shrink and heat up
e) Nothing. The only changes will be in the core
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AST201H1S FINAL EXAM, APRIL 2016
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ve
Which type of star has the shortest lifetime, and why?
6.
a)
A white dwarf, because it is very small and very hot
b)
A high-mass main sequence star, because it burns its fuel rapidly
c)
A low-mass main sequence star, because it has limited fuel to burn
d) An intermediate-mass main sequence star, because its atoms are ionized
e)
A neutron star, because gravity has forced it to collapse
7.
In a star cluster, all of the stars should be approximately the same:
a)
mass
b)
temperature
c)
age
d)
luminosity
e)
size
8.
Which of these is a difference between stars on the main sequence and stars not on the main
sequence?
a)
Main sequence stars fuse hydrogen in a shell and other stars do not
b)
Main sequence stars have fusion in their cores and other stars do not
c)
Main sequence stars fuse hydrogen in their cores and other stars do not
d) Main sequence stars are smaller than other stars
e)
Main sequence stars are cooler than other stars
9.
If a star sits in the top right corner of the HR diagram, which of the following must be true?
a) The star is large and luminous
b) The star is large and hot
c)
The star is cool and blue
d) The star is small and dim
e) The star is small and red
10. When a low-mass star is in the horizontal branch phase of its life, what is occurring in the star's
core?
a)
The core is fusing hydrogen to form helium
b)
The core is fusing hydrogen to form carbon
c)
The core is fusing helium to form carbon
d)
The core is not fusing, and is shrinking
e)
The core is not fusing, and is expanding
PAGE 3 OF 15
AST201H1S FINAL EXAM, APRIL 2016
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11. Why is there no helium fusion occurring in the Sun?
a)
The Sun doesn't contain enough helium to start helium fusion
b) The Sun is too luminous to fuse helium
c)
The Sun contains helium molecules, but not helium atoms
d) The Sun is not hot enough to fuse helium
e)
The Sun used to fuse helium, but all the helium has now been burnt
12. When the Sun becomes a red giant, why will its outer layers expand?
a)
Because of the extreme heat of hydrogen shell burning
b) Because helium weighs less than hydrogen
c)
Because the Sun' s mass will be lower than it is now
d) Because red stars are always larger than yellow stars
e)
Because electron degeneracy pressure forces the gas outwards
13. Which of these statements about low- and high-mass main-sequence stars is
FALSE?
a)
A low-mass star spends more time on the main sequence than a high-mass star
b) A low-mass star is smaller than a high-mass star
c)
A low-mass star is cooler than a high-mass star
d) A low-mass star produces a stronger force of gravity than a high-mass star
e)
A low-mass star is less luminous than a high-mass star
14. A white dwarf is:
a)
Hot, because the entire star is undergoing fusion
b) Dense, because it experiences gravity but not fusion
c) Luminous, because it is small and white
d)
Young, because it sits below the main sequence on the HR diagram
e)
Old, because it is hotter than a main sequence star
15. Main-sequence stars do not produce uranium (atomic mass 238) via nuclear fusion because:
a)
Stars never get hot enough to melt uranium
b) Uranium is radioactive, and decays before it can accumulate
c) Uranium is not a naturally occurring element
d) Fusing uranium requires energy rather than produces energy
e)
Uranium can only be made by fission of heavier elements
16. A supernova explosion occurs when:
a)
The iron core of a star collapses into a ball of neutrons
b)
The star's gravity decreases to the point where heat can blow the star apart
c)
A white dwarf collapses to form a black hole
d) Iron undergoes fission to make silicon and neon
e)
Helium begins fusing in a shell around the star's core
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AST201H1S FINAL EXAM, APRIL 2016
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17. Which of these groups of stars are very easy to see from Earth with the naked eye and why?
a)
White dwarfs, because they have very long lives
b) Giants and supergiants, because they are very luminous
c) Low-mass main sequence stars, because they are extremely common
d) Horizontal branch stars, because this is the main phase of evolution
e)
Stars in globular clusters, because that's where most stars reside
18. Which of the following is a correct summary of the gas-star-gas cycle?
a) Gas, white dwarf, supergiant, gas
b) Gas, horizontal branch star, main sequence star, gas
c) Gas, supernova, red giant, gas
d) Gas, low-mass star, supernova, gas
e) Gas, main sequence star, planetary nebula, gas
19. What happens when four hydrogen atoms are fused inside a star?
a)
A carbon atom is formed, and energy is converted into mass
b) A hydrogen molecule is formed, and light is absorbed
c)
An iron atom is formed, and no conversion of mass or energy can occur
d) A helium atom is formed, and some mass is converted into energy
e)
All the mass is converted into neutrinos, and energy is released
20. Describe the spectrum of a B star.
a)
A blackbody spectrum peaking at long visible wavelengths, with no absorption lines
b) A blackbody spectrum peaking at long visible wavelengths, with absorption lines
c)
A blackbody spectrum peaking at short visible wavelengths, with absorption lines
d) A blackbody spectrum peaking at short visible wavelengths, with emission lines
e)
A blackbody spectrum peaking at long visible wavelengths, with emission lines
21. If two 10 solar mass black holes collide, the result will be:
a)
A
neutron star
b)
A
larger black hole
c)
A
supernova
d)
A
supermassive black hole
e)
A
white dwarf
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AST201H1S FINAL EXAM, APRIL 2016
to
22. A woman is standing in a sealed room, and shines a laser against the far wall. She observes the
path of the laser beam to curve towards the ground. This could be because:
a)
She is in a reference frame travelling close to the speed of light
b) She is inside a black hole
c)
She is weightless
d) She is traveling at a constant speed
e)
She is in a gravitational field
23. According to Newton's Laws, what will happen to a rocket in deep space, far from any source
of gravity, if it shuts off its engine?
a)
It will travel in a straight line at constant speed
b)
It will slow down, and then come to a halt
c)
It will follow a curved path
d) Its clocks will begin running slower and slower
e)
The answer depends on your frame of reference
24. The centre of our Milky Way galaxy is 25,000 light years away. Describe what happens if you
you travel there and back at 99.99999999999% of the speed of light.
a)
You would die of old age before you reached the Milky Way's centre.
b)
You would make the trip in a few days, but from the Earth's perspective only a few minutes
would have passed
c)
Clocks on the ship would record that about 50,000 years had passed, but millions of years
would pass on Earth
d)
You would make the trip in a few days, but from your perspective it would be a 250,000
light year journey
e)
You would make the trip in a few days, but from the Earth's perspective about 50,000 years
would have passed
25. If we want to measure, with the shortest possible delay, what is going on in the core of the Sun,
which of the following should we measure and why?
a)
x-rays, because they are able to penetrate most normal matter
b) neutrinos, because they are weakly-interacting particles
c)
visible light, because the Sun makes so much of it
d)
infrared light, because it is not blocked by dust
e)
gamma rays, because they travel to Earth very quickly from the Sun
26. Which of the following can only be fully explained in a universe that began with a Big Bang?
a) the existence of hydrogen in the universe
b) the formation of elliptical galaxies by mergers
c) the cosmic microwave background
d) dark matter
e) dark energy
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AST201H1S FINAL EXAM, APRIL 2016
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27. According to our current understanding, which of the following best describes the ultimate fate
of our universe?
a)
expand until it reaches a maximum size, then recollapse
b)
expand until it reaches a maximum size, then maintain that size
c)
expand forever at a constant rate
d) expand forever at an ever-increasing rate
e)
we don't yet have enough information to predict the fate of the whole universe
28. Which of the following is not a significant difference between spiral and elliptical galaxies?
a)
spiral galaxies have arms and elliptical galaxies do not
b)
spiral galaxies are actively forming far more new stars than elliptical galaxies
c)
spiral galaxies tend to be much bluer in colour than elliptical galaxies
d)
spiral galaxies are much younger than elliptical galaxies, on average
e)
the largest spiral galaxies are smaller than the largest elliptical galaxies
29. Which of the following would be strong evidence contradicting Hubble's Law?
a)
ten galaxies with small blueshifts are found distributed all around the sky
b)
a hundred galaxies all in one part of the sky are found to have small blueshifts
c)
the redshifts and blueshifts of the nearest million stars are found to be almost random
d) thousands of galaxies all over the sky are found to have large redshifts
e)
all of the galaxies beyond 10 billion light years away have small blueshifts
30. Which of the following best describes the overall contents of the universe?
a)
70% dark energy, 25% dark matter, 5% normal matter
b) 90% dark matter, 10% normal matter
c)
70% dark matter, 25% dark energy, 5% normal matter
d) 70% hydrogen, 30% helium
e)
90% dark energy, 9% dark matter,
1
% normal matter
31. Dark matter is dark because it is:
a)
extremely cold, so that it doesn't emit light
b) unable to interact with light
c)
fully ionized, so it has no electrons with which to interact with light
d) extremely dense, so it blocks all light
e)
extremely far away, so we can't see whatever light it might be emitting
PAGE 7 OF 15
AST201H1S FINAL EXAM, APRIL 2016
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O
accelerate
d
o
e
e
32. Which of the following is a correct distinction between dark energy and dark matter?
a)
Dark energy is poorly understood; dark matter is well understood and can be produced in
labs
b) Dark energy can be seen; dark matter cannot be seen
c)
Dark energy accelerates the expansion of the universe; dark matter decelerates it
d)
Dark energy is well understood and can be produced in labs; dark matter is poorly
understood
e)
Dark energy is only present outside galaxies; dark matter is present everywhere
33. According to Hubble's Law, if a galaxy at a distance of
2
billion light years is moving away
from us at speed V, then a galaxy at a distance of 4 billion light years will be moving away
from us at speed:
a) V/4
b) V/2
c)
V
d) 2V
e) 4V
34. If the universe has more than the critical density, it will:
a) expand forever at a constant rate
b) definitely collapse
c) collapse or expand, depending on other factors
d) definitely expand forever
e) stop expanding
35. Which of the following best describes how galaxies are distributed throughout the universe?
a) galaxies are randomly scattered
b) there is a central cluster of galaxies and all of the other galaxies orbit this cluster
c)
galaxies are grouped into clusters, which are randomly distributed
d) galaxies are grouped into clusters, which are distributed in a web-like pattern
e)
galaxies are grouped into cluster, which are grouped into superclusters, which are grouped
into megaclusters, and so on, with no known limit to the maximum size of these structures
36. If Hubble's Law (showing distance vs. redshift for distant galaxies) remained a straight line all
the way out to the most distant observable galaxies, it would mean that:
a) The universe is infinite in size
b) The universe is not expanding
c) There is no dark energy in the universe
d) There was no big bang
e) Dark matter does not really exist
PAGE 8 OF 15
AST201H1S FINAL EXAM, APRIL 2016
o
C
37. Which of the following represents the rotation curve we should expect to see if a small number
of low-mass objects orbit a single very high-mass object?
distance from center of mass
distance from center of mass
A
e)
a>
a>
a.
l/
ł
>
d
i
s
t
a
n
c
e
f
rom
c
enter
o
f
m
a
ss
38. Earth contains significant quantities of heavy elements such as copper, zinc, and lead. Where
did these elements come from?
a) nuclear fusion in massive main-sequence stars
b) nuclear fission in massive main-sequence stars
c)
supernova explosions
d) nuclear fusion in white dwarf stars
e) nuclear fission in the Sun
39. The Voyager Golden Record contains a pulsar map that would allow anyone who found it to
locate Earth. Why are pulsars appropriate for this purpose?
a)
Pulsars are the most common type of star, so they are good reference points.
b)
Earth is in a part of the Milky Way that has an unusually high density of pulsars.
c)
Pulsars will tend to attract attention when they explode as supernovae.
d) Pulsars can be accurately identified by their rotation periods.
e)
Pulsars are extremely large stars and are therefore easily seen from anywhere in the Milky
Way.
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AST201H1S FINAL EXAM, APRIL 2016
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a
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40. The most common form of iron has 56 nucléons in its nucleus (a nucléon is a proton or a
neutron). Which of the following reactions would
PRODUCE
energy? You may wish to refer
to the following graph.
a
t
o
m
i
c
m
a
ss
(
n
u
mb
e
r
o
f
p
r
o
t
o
n
s
and
n
e
u
t
r
o
n
s
)
a) fission of oxygen (16 nucléons)
b) fusion of two zinc atoms (64 nucléons each)
c)
fusion of two oxygen atoms (16 nucléons each)
d) fusion of an oxygen atom with a zinc atom
e)
fusion of two uranium atoms (238 nucléons each)
41. Which of the following is
NOT
part of the lifecycle of a 2 solar-mass star?
a) planetary nebula
b) main sequence star
c) red giant star
d) inert core supported by degeneracy pressure
e)
supernova
42. The main difference between a cosmological redshift (CR) and a Doppler redshift (DR) is that:
a)
CRs are found only in nearby galaxies, while DRs are found only in distant ones
b)
CRs are caused by expansion of space, while DRs are caused by motion through space
c)
CRs are caused by spacetime curvature, while DRs are caused by gravity
d)
CRs are caused by motion of objects away from us, while DRs are caused by motion of
objects toward us
e)
the theory of CRs has completely replaced the theory of DRs in the same way the theory of
relativity has replaced Newton's law of gravity
PAGE
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AST201H1S FINAL EXAM, APRIL 2016
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a
43. Which of the following constitutes the minimum explanation required to account for the fact
that the observable universe has a finite size (i.e. that it is not infinitely large)?
a) The speed of light is finite.
b)
The size of the telescopes we can build is finite.
c)
The age of the universe is finite and the speed of light is finite.
d)
The length of time that we have been observing the universe is finite.
e)
The size of the telescopes we can build is finite and the speed of light is finite.
44. Which of the following is closest to our best current estimate for the age of the universe?
a)
1.4 million years
b)
140 million years
c)
1.4 billion years
d)
14 billion years
e)
140 billion years
45. Imagine we observe two Type la supernovae from the moment of their explosion until several
weeks afterward. We measure that the maximum apparent brightness of supernova X is nine
times that of supernova Y. What can we conclude for certain?
a)
Supernova X was the explosion of a massive star, while supernova Y was the explosion of a
low-mass star.
b)
Supernova X was three times closer to us than supernova Y.
c)
Supernova X began with a white dwarf, while supernova Y began with a neutron star.
d)
Supernova X took place in the Milky Way, while supernova Y took place in another galaxy.
e)
Supernova X had a higher luminosity than supernova Y.
46. If we want to measure the distance to a galaxy 10 billion light years away, which of the
following would be the most accurate method that is feasible with current technology?
a)
Measure the parallax of a star in that galaxy.
b)
Send a probe to the galaxy and track its motion using onboard gyroscopes.
c)
Measure the surface temperature of an O star in the galaxy, locate it on the main sequence,
use that to determine its luminosity, and compare to its apparent brightness.
d)
Measure the luminosity of a Type la in that galaxy and compare to its apparent brightness.
e)
Measure the Doppler shift of the galaxy and calculate its distance using the Doppler effect
formula.
PAGE 104 OF 15
AST201H1S FINAL EXAM, APRIL 2016
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47. Imagine we discover a galaxy like the Milky Way, but with no dark matter. What general
pattern should we expect to see in the motions of its stars?
a)
Stars in the bulge should all remain stationary with respect to one another.
b)
Stars in the halo should orbit faster than stars in the bulge.
c)
Stars on the outer edge of the disk should orbit slower than stars near the bulge.
d)
Stars in the bulge should be in clusters while stars in the halo should not be in clusters.
e)
Stars in the disk should all have the same orbital period.
48. Which of the following lists correctly orders the stellar spectral classes from shortest to longest
main-sequence lifetime?
a)
ABOFGKM
b)
OABGKFM
c)
OBAFGKM
d)
MKGFABO
e)
MKFGBAO
49. Which of the following celestial events will occur first?
a) The Sun leaves the main sequence.
b) The Milky Way collides with Andromeda.
c)
The Sun completes another orbit around the center of the Milky Way.
d) The accelerating expansion of space makes it impossible to observe galaxies outside the
Local Group.
e)
The nearby 45 solar mass star WR 102c explodes as a supernova.
50. Which of the following lists best describes the major components of a spiral galaxy?
a) clusters and gas
b) halo, disk, and bulge
c) disk, clusters, and gas
d) disk, globular clusters, and open clusters
e) bar, halo, and bulge
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PART B: Short answer questions. Answer the following questions in the space provided. Point
form is acceptable where appropriate. Marks may be deducted for lack of clarity or concision.
51. Dark energy.
a)
[2 marks] Describe, in your own words, a single line of evidence for the existence of dark
energy.
b)
[2 marks] If there was no dark energy in our universe and never had been any, what effect
would this have had on the expansion of the universe?
52. The Big Bang model.
a)
[2 marks] According to the Big Bang model, where is the centre of the universe?
Briefly
explain your answer.
b) [1 mark]
Name
one key piece of evidence for the Big Bang model
other than Hubble's
Law.
c)
[2 marks]
Explain
how your answer from part (b) supports the Big Bang model, and how it
rules out models of the universe that did not begin with a big bang.
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AST201H1S FINAL EXAM, APRIL 2016
53. Spectroscopy.
a)
[3 marks] Draw a
CLEARLY LABELED
diagram that illustrates how a single star and a
gas cloud can produce either a continuous spectrum or an absorption spectrum, depending
on the angle from which they are viewed. Your diagram must include clear indications of
the two points of view that produce the two different types of spectra.
b)
[2 marks] Explain how we can use the spectrum of a galaxy to determine whether the galaxy
is moving toward or away from us. If you choose to use a diagram (optional), make sure it is
clearly labeled.
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AST201H1S FINAL EXAM, APRIL 2016
54. [6 marks] The following diagram shows the axes for a Hertzsprung-Russell diagram. The dot
indicates the position of the Sun. Add all of the following to the diagram, being careful to
CLEARLY LABEL
each one.
a)
[2 marks] Label each axis with an axis name and the approximate range of values being
plotted on that axis. For example, if you were plotting the capacity of gas tanks, you would
write "Gas tank capacity" and then markers for various capacities, such as 10 L, 100 L,
1000 L
b)
[1 mark] Sketch the main sequence.
c)
[1 mark] Outline the region of the diagram occupied by giants and supergiants.
d)
[1 mark] Outline the region of the diagram occupied by white dwarfs.
e)
[1 mark] Outline where we would find a star that is late in its life cycle and whose spectrum
has many lines from molecules (as opposed to atoms)
THE END ~ TOTAL MARKS 70
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