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School
University of Pittsburgh *
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Course
0089
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
12
Uploaded by ProfessorEmu432
Name
Peoplesoft #
Exam 2
- Version D (Blue)
Astronomy 0089: Stars, Galaxies, and the Cosmos
1. Fill in your Name and Peoplesoft ID number
on this test
(above) and
on the scantron
form
–
be sure to bubble in the Peoplesoft ID.
2. Please fill in your name and
SIGNATURE
on your answer sheet. Your signature
affirms that you will not share the contents of this exam with anyone outside class.
2. Be sure to answer the last two questions correctly. Getting these questions right will
ensure your exam is graded properly.
3.
ALWAYS SELECT THE BEST ANSWER.
There is only one best answer for each
question. Read each question carefully before answering.
4. Be sure to answer all questions; no points are deducted for guessing.
5.
If you have any questions,
please
raise your hand and ask them when we come to
you.
6.
Return this exam booklet
along with the scoresheet when you are done with the
exam
This exam has extra proportionality questions at the end to give you plenty of
opportunity to practice.
I expect our actual exam to have roughly 30-35
questions in total, of which 4-5 may apply proportionalities directly.
1. Suppose you find a binary star consisting of Stars A and B orbiting each other with a
semimajor axis of 1 AU.
Each star has a mass half as large as the Sun.
What would their
orbital period be?
A) A and B would each have different orbital periods
B) Between 10 and 100 years
C) 1 year
D) Between 1 and 10 years
E) Less than one year
2. Two stars, Thuban and SUPERBLINK 23261+1600, each have a surface temperature
of 10000 K.
Which star has a greater luminosity?
A) The luminosities of the two stars must be the same
B) Insufficient information has been provided to determine the answer
C) Thuban
D) SUPERBLINK 23261+1600
3. During a total solar eclipse, you can see the low-density outer atmosphere of the Sun,
which you normally cannot see from Earth.
What is this atmosphere called?
A) Radiative zone
B) Penumbra
C) Corona
D) Photosphere
E) Core
4. Mira is a star with about the same mass as the Sun.
What color is it?
A) Yellow
B) You can't answer this question with the information given
C) Blue
D) Red
E) Green
5. How can we measure the masses of stars?
A) You would need to go there and use a really big scale
B) If you know the star's color, you can use that to calculate its mass- all stars of
the same color have the same mass
C) By observing the orbits of binary stars
D) If you know the star's luminosity, you can always use that to calculate its mass
E) c and d
6. The stars Canopus and Alpha Centauri have about the same apparent brightness.
What
can we say about their luminosities?
A) You would have to know their distances to know which has a higher
luminosity
B) You would have to know if they are both ideal thermal emitters to know which
has a higher luminosity
C) They must be about the same
D) You would have to know their colors to know which has a higher luminosity
E) You would have to know their radii to know which has a higher luminosity
7. How does the Sun produce energy?
A) By fission of uranium into lighter elements
B) Energy is being produced in different ways in different layers of the Sun
C) By fusion of hydrogen into helium
D) By fusion of helium into carbon
E) By chemical reactions of hydrogen and oxygen into water
8. Saturn is 10 AU from the Sun.
How bright would the Sun appear from Saturn,
compared to how it appears on Earth?
A) It would be 10 times as bright
B) It would be 1/1000 as bright
C) It would have the same brightness, as its luminosity is the same
D) It would be 1/10 as bright
E) It would be 1/100 as bright
9. How is energy transferred through the radiative zone of the Sun?
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A) The Sun's energy is generated in the radiative zone and is transferred through
other zones
B) It is transferred by blobs of hotter material rising and cooler material sinking
C) It is transferred by light traveling outward
D) It is transferred by direct thermal contact between material, like hot coffee
heating up the mug it is in
10. Why do stars have different colors?
A) Hotter stars appear bluer and cooler stars appear redder
B) Hotter stars appear redder and cooler stars appear bluer
C) Higher-mass stars appear redder and lower-mass stars appear bluer
D) Higher-luminosity stars appear bluer and lower-luminosity stars appear redder
E) Higher-mass stars appear bluer and lower-mass stars appear redder
11. Where is energy being generated in the Sun?
A) Radiative zone
B) Convective zone
C) The Sun generates energy throughout its interior
D) Photosphere
E) Core
12. Betelgeuse and Lalande 21185 appear exactly the same color, but Betelgeuse has a
much higher luminosity than Lalande 21185.
What can we conclude from this?
A) Betelgeuse has a lower surface temperature than Lalande 21185
B) Betelgeuse has a smaller radius than Lalande 21185
C) Betelgeuse has a higher surface temperature than Lalande 21185
D) Betelgeuse has a larger radius than Lalande 21185
E) Betelgeuse has a larger mass than Lalande 21185
13. What do we mean when we say that the Sun is in hydrostatic equilibrium?
A) The force of pressure from within the Sun is in balance with the force of
gravity, so the Sun stays about the same size
B) The force of gravity is in balance with the static electricity generated by the
Sun's magnetic field, so the Sun stays about the same size
C) The temperature of the Sun is the same throughout its interior
D) The Sun is at the center of the solar system and is not moving
E) Plumes of water rise and sink in the Sun's interior, and transport energy from
the core to the surface
14. Which of the following is a type of observation that has allowed us to learn about the
interior structure of the Sun?
A) Observations of the orbits of the planets
B) Observations of oscillations of the Sun (helioseismology)
C) Observations from space probes that were dropped into the Sun
D) Measurements of the spectrum of sunlight
15. How can we determine the surface temperature of a distant star?
A) From its apparent brightness
B) From the orbit of a planet or binary companion around it
C) We can't, we would need to go there with a thermometer to find out
D) From its color
E) From its luminosity
16. The star Adhara is a Main Sequence star with a mass roughly 10 times as large as the
mass of the Sun.
How should its Main Sequence lifetime compare to that of the Sun?
A) Adhara will be on the Main Sequence about 1/1000 (one one-thousandth) as
long as the Sun
B) Adhara will be on the Main Sequence about the same amount of time as the
Sun
C) Adhara will be on the Main Sequence about 1/10 (one tenth) times as long as
the Sun
D) Adhara will be on the Main Sequence about 1/10,000 (one ten-thousandth)
times as long as the Sun
E) Adhara will be on the Main Sequence about 1/100 (one one-hundredth) times
as long as the Sun
17. What force prevents white dwarfs from collapsing?
A) Neutron degeneracy pressure
B) Electron degeneracy pressure
C) Electrical repulsion between negatively charged electrons
D) Radiation pressure
E) Centrifugal force
18. As the Sun evolves off the Main Sequence, it will lose some of its mass due to
increased solar wind.
Based on Newton’s version of Kepler’s Third Law, what will
happen to the length of an Earth year after this happens as a result of this change in mass,
assuming the semimajor axis of the Earth’s orbit remains unchanged?
A) All of the planets will be vaporized by the explosion that will happen when the
Sun leaves the Main Sequence, so Earth will not have a year
B) It will be longer
C) It will stay the same
D) It will be shorter
19. Kappa Persei is a horizontal branch star with about the same mass as the Sun.
What
kind of fusion is most likely going on inside it now, and how is it likely to evolve in the
future?
A) It is now fusing helium in its core with no other fusion taking place.
When it
uses up the helium in the core, it will lose its outer layers and become a neutron star or a
black hole.
B) It is not fusing anything in its core.
When it becomes hot enough to fuse
helium, it will move back onto the Main Sequence with about the same luminosity and
temperature as it had before it became a horizontal branch star.
C) It is now fusing helium in its core with hydrogen fusion in a shell around the
core.
When it uses up the helium in the core, it will lose its outer layers and become a
white dwarf.
D) It is now fusing silicon into iron in its core, with other types of fusion taking
place in layers around the core.
When it uses up the silicon in its core, it will become a
supernova.
E) It is now fusing hydrogen in its core with helium fusion in a shell around the
core.
When it uses up the hydrogen in the core, it will lose its outer layers and become a
white dwarf.
20. Betelgeuse is a type M star, while the Sun is a Type G star.
Based on this, which of
the following could describe the color of Betelgeuse as your eyes see it?
A) There is insufficient information to determine the answer, as you would have
to know each star's mass
B) Red
C) Green
D) Blue
21. The Interstellar Medium is made up primarily of what?
A) Gas and Dust
B) Stars
C) Black Holes
D) Nothing, the Interstellar Medium is a vacuum and does not have anything in it
E) Interstellar comets like the recently discovered Comet 2I/Borisov
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22. What happens to the hydrogen in a star as it nears the end of its Main Sequence
lifetime?
A) As soon as a star begins to leave the Main Sequence, the hydrogen in its outer
layers is blown away from the star, forming a planetary nebula
B) The hydrogen in the core of the star has been fused into helium, but there is
still hydrogen outside the core of the star
C) The star's energy source changes from hydrogen fusion to helium fission,
which replenishes the hydrogen in the star
D) The hydrogen at the surface of the star has been fused into helium, but there is
still hydrogen in the core of the star
E) All of the hydrogen in the star has been fused into helium
23. What is a protostar?
A) A theoretical model of how a star works
B) An opaque object that will become a star, but is not yet fusing hydrogen into
helium
C) A cold, dense cloud of gas from which stars may eventually form
D) A star that does not have sufficient mass to fuse ordinary hydrogen into helium
E) A dense object made up entirely of protons, left after a supernova explosion
24. Which of the following stars (which may or may not be on the Main Sequence) will
have the highest luminosity?
A) The Sun, a type G star
B) Antares, a type M star
C) There is not enough information given here to determine the answer
D) Vega, a type A star
E) Spica, a type B star
25. Which of the following is NOT true of all main sequence stars?
A) They are supported by electron degeneracy pressure
B) They are opaque objects (i.e., they are not transparent to any form of light)
C) They are in a state of hydrostatic equilibrium
D) They are fusing hydrogen to helium in their core
E) They can be treated as ideal thermal emitters, and so appear bluer if they have
a higher surface temperature
26. Which of the following Main Sequence stars will have the lowest mass?
A) Rigel, a type B star
B) The Sun, a type G star
C) Proxima Centauri, a type M star
D) There is not enough information given here to answer the question
E) Sirius, a type A star
27. How do the masses of red giants compare to the masses of Main Sequence stars?
A) Red giants all have about the same mass as the Sun, but much larger radii
B) Because red giants have low surface temperatures, they are less massive than
most Main Sequence stars
C) Main Sequence stars evolve into red giants, so red giants have about the same
mass as the Main Sequence stars they evolve from
D) Red giants have about the same mass as the largest Main Sequence stars, but
all red giants are much more massive than the Sun
E) Red giants are much more massive than Main Sequence stars, and are larger
for that reason
28. What prevents most interstellar gas from collapsing to form stars?
A) It contains too much dust to form stars
B) It is made up of gas molecules, and stars can only form from hydrogen gas
C) Stars are not formed from collapsing interstellar gas
D) It is too hot
E) It is too cold
29. How do the luminosities and surface temperatures of sun-like stars change in the
stage just after they leave the Main Sequence?
A) The stars become less luminous and will have a higher surface temperature
B) We are unable to predict what will happen as the Sun hasn't left the main
sequence yet
C) The stars become more luminous and will have a lower surface temperature
D) The stars become more luminous and will have a higher surface temperature
E) The stars become less luminous and will have a lower surface temperature
30. What is a planetary nebula?
A) A clump in a disk of dust and gas surrounding a young star, which can form
into a planet
B) Gas from the outer part of a red giant ejected during its last stages of evolution
C) A disk of material that is swirling around a black hole
D) A disk of dust and gas surrounding a young star, that can form into planets
E) A massive cloud of cold gas from which stars can form
31. Use the indicated stars (A-E) on the Hertzsprung-Russell Diagram to answer this
question and the next two questions.
Which star has the largest radius?
A) A
B) B
C) C
D) D
E) E
32. Sirius B is a 1 solar mass white dwarf.
Which position might it occupy on the H-R
diagram?
A) A
B) B
C) C
D) D
E) E
33. Which Main Sequence star will have the shortest lifetime?
A) A
B) B
C) C
D) D
E) E
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34. Why isn't Jupiter a star?
A) Jupiter is not massive enough to fuse any form of hydrogen into helium
B) Jupiter is orbiting the Sun, and objects that orbit stars are planets, not stars, by
definition
C) Jupiter was once a star, but has since burned out
D) Jupiter could become a star if it reaches hydrostatic equilibrium at some point
in the future but this hasn't happened
E) Jupiter does not comprise the majority of mass in its orbit, so it cannot be a star
35. Which of the following stars (which may or may not be on the Main Sequence) has
the highest surface temperature?
A) Spica, a type B star
B) Betelgeuse, a type M star
C) Vega, a type A star
D) There is not enough information given here to determine the answer
E) The Sun, a type G star
Some extra questions applying various proportionality relationships:
1. Stars A and B have the same temperature, and B has a luminosity 4 times as high as
Star A's.
How do the radii of the two stars compare?
A) Star A is 2 times larger than Star B
B) Star B is 2 times larger than Star A
C) Star A is 4 times larger than Star B
D) Star B is 4 times larger than Star A
E) Since they have the same temperature, they must be the same size
2. The stars Alpha Centauri B and Tau Ceti both have the same luminosity.
The radius of
Tau Ceti is smaller than that of Alpha Centauri B.
Which star will have a larger surface
temperature?
A) The temperatures of the two stars must be the same
B) Insufficient information has been provided to determine the answer
C) Alpha Centauri B
D) Tau Ceti
3. You discover a planet going around star X that has an orbit with a semimajor axis of 1
AU. You find that this planet takes 24 months to complete an orbit.
Based on what you
found, which of the following must be true?
A) Star X is less massive than the Sun
B) Star X has the same mass as the Sun, since it has a planet with semimajor axis
1 AU
C) This information is not sufficient to draw any conclusions about Star X’s mass
D) Star X is more massive than the Sun
4. Imagine you discover an asteroid which orbits the Sun once every six months.
How
large must the semi-major axis of its orbit be, compared to the semi major axis of the
Earth's orbit?
A) the semi-major axis will be the same (1 AU)
B) the semi-major axis will be larger than the Earth's
C) the semi-major axis will be smaller than the Earth's
5. Astronomers recently discovered a planet orbiting the star HD 175541, which has a
mass of 1.65 times the mass of the Sun.
This planet has roughly the same mass as
Jupiter, and its orbit has a semimajor axis of 1 AU.
How long will this planet take to
orbit HD 175541?
A) More than one year
B) Less than one year
C) One year
D) There is insufficient information to answer this question
6. The planet Mars is 1.52 AU from the Sun.
How bright will the Sun appear from Mars,
compared to its apparent brightness at the Earth?
A) The Sun will appear just as bright from Mars as it does from the Earth
B) The Sun will appear 1.52 times brighter at Mars
C) The Sun will appear 1.52 times fainter at Mars
D) The Sun will appear 1.52
2
= 2.32 times brighter at Mars
E) The Sun will appear 1.52
2
= 2.32 times fainter at Mars
7. The star Capella, visible in the winter sky, is the same color as the Sun. Capella is
more luminous than the Sun. This tells us that Capella is ________ than the Sun.
A) Smaller
B) Hotter
C) Colder
D) Larger
8. Epsilon Eridani , one of the closest stars to the Sun, is a main sequence star of spectral
type K, with a surface temperature of roughly 5000 K and a radius of about 0.8 (= 8x10
-
1
) R
Sun
.
Pollux, the brightest star in the constellation Gemini, is a giant star of spectral
type K, with a surface temperature of roughly 5000 K and a radius of about 8 R
Sun
.
How does the luminosity of Pollux compare to the luminosity of Epsilon Eridani?
A) Pollux will be 100 (10
2
) times more luminous
B) Pollux will be 10 (10
1
) times less luminous
C) Pollux will be 10,000 (10
4
) times more luminous
D) Pollux will be 10 (10
1)
times more luminous
E) There is insufficient information to answer this question
9. The stars Tau Ceti and Epsilon Eridani are both similar in luminosity to our
Sun. Epsilon Eridani is approximately twice as far away as Tau Ceti. What can we say
about the relative brightnesses of these stars as seen from Earth?
A) They will both be the same brightness, since they both have the same luminosity
B) Tau Ceti will be about four times as bright as Epsilon Eridani
C) Tau Ceti will be about twice as bright as Epsilon Eridanic.
D) Epsilon Eridani will be about four times as bright as Tau Ceti
E) Epsilon Eridani will be about twice as bright as Tau Ceti
10. Suppose we discover an Earth-like planet orbiting its star in an orbit with semimajor
axis of 1 AU.
Each orbit takes one-half of a year (0.5 years, or 2
-1
years) to complete.
What must the mass of its parent star be?
A) 0.25 (= 2
-2
) solar masses
B) 0.5
(= 2
-1
)
solar masses
C) 4 (= 2
2
) solar masses
D) 2
(= 2
1
) solar masses
E) 1
(= 2
0
) solar mass
11. Capella B has about the same surface temperature as the Sun, but 9 times the radius
of the Sun. How will its luminosity compare to the Sun's?
A) Its luminosity will be 9 times the luminosity of the Sun
B) Its luminosity will be 81 (9
2
) times the luminosity of the Sun
C) It will have the same luminosity, since it has the same surface temperature
D) Its luminosity will be 6561 (9
4
) times the luminosity of the Sun
12. You measure the parallaxes of two stars, A and B.
You determine that A has a
parallax angle of 0.1 arcseconds and B has a parallax angle of 0.01 arcseconds.
How do
their distances from us compare?
A) Star A is 100 times further away than star B
B) Star A is 10 times further away than star B
C) They are the same distance from us
D) Star B is 10 times further away from us than star A
E) Star B is 100 times further away from us than star A
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