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ASTR 150 ACTUAL QUESTIONS
2026 WITH VERIFIED ANSWERS.
1. The Hyugen's probe detected a spike in methane as it
touched down on a solid surface on Titan. What did this
imply about the area in which the probe landed? - correct
answer-It landed at low tide
2. If geologic activity scales with size, why do small satellites
(smaller than the Moon) like Ariel and Titania show signs of
very recent geologic activity and the Moon does not? -
correct answer-Their surfaces are different composition than
the Moon
3. Nitrogen and methane are the main constituents of Titan's
atmosphere. Titan's atmosphere is opaque to visible light,
but nitrogen and methane are colorless gasses. Why can't
we see the surface of Titan in visible wavelengths? - correct
answer-Photodissociation of methane produces smog
4. The surface composition of all of the worlds of the outer
Solar System is predominantly - correct answer-water ice
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5. Why is Io the only solid surface in the Solar system that is
completely devoid of impact craters? - correct answer-The
surface is constantly being resurfaced, covering all impact
craters
6. Neptune's moon, Triton, has active volcanoes on the surface.
The most probable energy source for these volcanoes is -
correct answer-the Sun
7. Please refer to the following figure and review the Kepler's
Laws activity from Lesson Module 3 for the next six (6)
questions (Questions 3-8) - correct answer-
8. In the figure above, at which point is the tidal force on the
blue moon the greatest? - correct answer-A
9. In the figure above, at which point is the tidal force on the
blue moon the least? - correct answer-C
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10. In the above figure, at which point is the blue moon
moving fastest in its orbit? - correct answer-A
11. In the figure above, at which point is the blue moon
moving slowest in its orbit? - correct answer-C
12. In the figure above, pretend that the yellow object is a star
with the same mass as our Sun. The blue object is a planet
orbiting this star. You determine the planet's orbital period to
be 4 years. Approximately how far (ie. its semi-major axis)
from the star is this planet (in AU)? - correct answer-2.5
13. In the figure above, again pretend that the yellow object is
a star with the same mass as the Sun and the blue object is
a planet orbiting this star. The blue planet is located at 3 AU
from the star. What is the blue planet's approximate orbital
period in years? - correct answer-5.2
14. Neptune's satellite, Triton, looks like a common "regular"
giant planet satellite, but you learned that it is actually an
irregular satellite. Which of the following is one of the
reasons we suspect that Triton is not a regular satellite? -
correct answer-It is in a retrograde orbit
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15. Io's orbit is in 2:1 resonance with the orbit of Europa and
in 4:1 resonance with the orbit of Ganymede. The period of
Io's orbit is 1.8 days. What then, must be the orbital periods
of Europa and Ganymede? - correct answer-Europa = 3.6
days and Ganymede = 7.2 days
16. You now understand a great deal more about tidal forces
than when we first encountered them while discussing the
Earth's Moon. Recall that I said that the tidal force on the
Earth due to the Moon is twice that of the tidal force on Earth
due to the Sun. How can this be when the Sun is much,
much more massive than the Earth's Moon? - correct
answer-The Moon is much closer to the Earth than the Sun
17. Jupiter's regular satellites, Io and Europa, are geologically
active today because their interiors are heated by - correct
answer-gravitational interactions with Jupiter and its other
satellites
18. Astronomers estimate that there may be as many as a
trillion cometary objects (KBOs) in the Kuiper Belt. Despite
their large numbers, the majority of known KBOs have only
been discovered in the last decade. Why is this? - correct
ASTR 150 ACTUAL QUESTIONS
2026 WITH VERIFIED ANSWERS.
1. The Hyugen's probe detected a spike in methane as it
touched down on a solid surface on Titan. What did this
imply about the area in which the probe landed? - correct
answer-It landed at low tide
2. If geologic activity scales with size, why do small satellites
(smaller than the Moon) like Ariel and Titania show signs of
very recent geologic activity and the Moon does not? -
correct answer-Their surfaces are different composition than
the Moon
3. Nitrogen and methane are the main constituents of Titan's
atmosphere. Titan's atmosphere is opaque to visible light,
but nitrogen and methane are colorless gasses. Why can't
we see the surface of Titan in visible wavelengths? - correct
answer-Photodissociation of methane produces smog
4. The surface composition of all of the worlds of the outer
Solar System is predominantly - correct answer-water ice
, Page | 2
5. Why is Io the only solid surface in the Solar system that is
completely devoid of impact craters? - correct answer-The
surface is constantly being resurfaced, covering all impact
craters
6. Neptune's moon, Triton, has active volcanoes on the surface.
The most probable energy source for these volcanoes is -
correct answer-the Sun
7. Please refer to the following figure and review the Kepler's
Laws activity from Lesson Module 3 for the next six (6)
questions (Questions 3-8) - correct answer-
8. In the figure above, at which point is the tidal force on the
blue moon the greatest? - correct answer-A
9. In the figure above, at which point is the tidal force on the
blue moon the least? - correct answer-C
, Page | 3
10. In the above figure, at which point is the blue moon
moving fastest in its orbit? - correct answer-A
11. In the figure above, at which point is the blue moon
moving slowest in its orbit? - correct answer-C
12. In the figure above, pretend that the yellow object is a star
with the same mass as our Sun. The blue object is a planet
orbiting this star. You determine the planet's orbital period to
be 4 years. Approximately how far (ie. its semi-major axis)
from the star is this planet (in AU)? - correct answer-2.5
13. In the figure above, again pretend that the yellow object is
a star with the same mass as the Sun and the blue object is
a planet orbiting this star. The blue planet is located at 3 AU
from the star. What is the blue planet's approximate orbital
period in years? - correct answer-5.2
14. Neptune's satellite, Triton, looks like a common "regular"
giant planet satellite, but you learned that it is actually an
irregular satellite. Which of the following is one of the
reasons we suspect that Triton is not a regular satellite? -
correct answer-It is in a retrograde orbit
, Page | 4
15. Io's orbit is in 2:1 resonance with the orbit of Europa and
in 4:1 resonance with the orbit of Ganymede. The period of
Io's orbit is 1.8 days. What then, must be the orbital periods
of Europa and Ganymede? - correct answer-Europa = 3.6
days and Ganymede = 7.2 days
16. You now understand a great deal more about tidal forces
than when we first encountered them while discussing the
Earth's Moon. Recall that I said that the tidal force on the
Earth due to the Moon is twice that of the tidal force on Earth
due to the Sun. How can this be when the Sun is much,
much more massive than the Earth's Moon? - correct
answer-The Moon is much closer to the Earth than the Sun
17. Jupiter's regular satellites, Io and Europa, are geologically
active today because their interiors are heated by - correct
answer-gravitational interactions with Jupiter and its other
satellites
18. Astronomers estimate that there may be as many as a
trillion cometary objects (KBOs) in the Kuiper Belt. Despite
their large numbers, the majority of known KBOs have only
been discovered in the last decade. Why is this? - correct
