Download Astronomy 1400: Exam 3 version 1

Astronomy 1400: Exam 3 version 1
Instructions: Choose the best answer to each multiple choice problem below.
1. Based on our current theory of Earth’s formation, the water we drink comes from . . .
A. . . . ice that condensed in the solar nebula in the region where Earth formed.
B. . . . chemical reactions that occurred in Earth’s crust after Earth formed.
C. . . . chemical reactions that occurred in Earth’s core after Earth formed.
D. . . . material left behind during the giant impact that formed the Moon.
E. . . . comets that impacted Earth.
2. Why isn’t there a planet where the asteroid belt is located?
A. There was not enough material in this part of the solar nebula to form a planet.
B. A planet once formed here, but it was broken apart by a catastrophic collision.
C. Gravitational tugs from Jupiter prevented material from collecting together to form a
planet.
D. There was too much rocky material to form a terrestrial planet, but not enough gaseous
material to form a jovian planet.
E. The temperature in this portion of the solar nebula was just right to prevent rock from
sticking together.
3. Which of the following most likely explains why Venus does not have a strong magnetic field?
A.
B.
C.
D.
E.
It does not have a metallic core.
Its rotation is too slow.
It is too close to the Sun.
It is too large.
It has too thick an atmosphere.
4. Why is the internal temperature of Io so high?
A. It is a very large moon and so cools very slowly.
B. Jupiter’s strong gravity attracted the planetesimals more strongly than Io and bombarded
it with many objects, heating it up.
C. Io is so close to Jupiter that tidal forces heat it up even though it is a small moon.
D. Io has a thick atmosphere of greenhouse gases that keeps the internal temperature high.
E.
5. Which of the following is NOT an important way to add gas to a terrestrial planets atmosphere?
A. Outgassing of material from volcanic activity
B. Evaporation or sublimation of surface liquids and solids
C. Accretion of gas during planet formation
D. Vaporization of materials from micrometeorite impacts
Page 1 of 9
6. Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
A. Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate
rocks rather than being free in the atmosphere.
B. Earth has just as much carbon dioxide as Venus, but it is hard to detect because Earth’s
atmosphere is so much colder than Venus.
C. Earth’s volcanoes outgassed far less carbon dioxide than those on Venus.
D. Earth once had a lot of carbon dioxide, but it was lost to space during the heavy bombardment early in our solar system’s history.
E. Chemical reactions turned Earth’s carbon dioxide into nitrogen.
7. Potassium spontaneously decays to Argon with a half life of 1.3 billion years. About what
fraction of potassium should be left in a sample of a meteorite formed at the start of the
Solar System 4.6 billion years ago?
A. ∼ 50% B. ∼ 25% C. ∼ 10% D. ∼ 1% E. ∼ 0.1%
winds from the Coriolis effect because it rotates so
.
8. Venus has
A. strong, quickly B. strong, slowly C. weak, quickly D. weak, slowly
9. What is the Great Red Spot?
A.
B.
C.
D.
a storm that comes and goes on Jupiter
a long-lived, high-pressure storm on Jupiter
a place where reddish particles from Io impact Jupiter’s surface
a region on Saturn where the temperature is so high that the gas glows with red visible
light
E. a storm on Saturn where particles are constantly flowing downward so fast that they are
Doppler-shifted red
10. Why does the Doppler technique for finding extrasolar planets give only a minimum velocity?
A. The size of the Doppler shift that we detect depends on how the planet’s orbit is tilted
compared to our line of sight.
B. The size of the Doppler shift that we detect depends on knowing the star’s mass, which
can be very uncertain.
C. Extrasolar planets are always increasing in velocity.
D. Doppler measurements are very difficult, producing noisy data that often cause astronomers to underestimate a planet’s velocity.
E. Others stars passing by frequently pull on the planets.
11. Olympus Mons is . . .
A. . . . a large valley on the Moon. B. . . . a vast plain on Mars. C. . . . a huge series of
cliffs on Mercury.
D. . . . the largest volcano in the Solar System, on Mars.
E. . . . the
largest volcano in the Solar System, on Venus.
Page 2 of 9
12. The sky is blue because . . .
A.
B.
C.
D.
E.
...
...
...
...
...
molecules scatter blue light more effectively than red light.
molecules scatter red light more effectively than blue light.
light bounces off the blue water on the ground (oceans, lakes, etc.).
the atmosphere transmits mostly blue light.
the atmosphere absorbs mostly blue light.
13. According to our theory of solar system formation, which law best explains why the solar
nebula spun faster as it shrank in size?
A.
B.
C.
D.
E.
the conservation of mass
the conservation of angular momentum
the conservation of energy
Newton’s law of gravity
Einstein’s law E = mc2
14. Earth’s carbon dioxide cycle operates over a timescale of . . .
A.
B.
C.
D.
E.
...
...
...
...
...
a
a
a
a
a
few
few
few
few
few
weeks.
years.
centuries.
millennia.
hundred thousand years.
15. Why does atmospheric pressure decrease as you go higher in altitude on Earth?
A.
B.
C.
D.
Gravity gets much weaker with altitude.
The weight of the atmosphere above you decreases with altitude.
Temperature decreases with altitude and lower temperature tends to mean lower pressure.
There are fewer greenhouse gases at higher altitude.
16. Heat escapes from a planet’s surface into space by thermal radiation. Planets radiate almost
entirely in the wavelength range of the . . .
A. . . . infrared. B. . . . radio. C. . . . visible. D. . . . ultraviolet. E. . . . X-ray.
17. Why is Saturn almost as big as Jupiter, despite its smaller mass?
A.
B.
C.
D.
Jupiter’s greater mass compresses it more, thus increasing its density.
Saturn’s rings make the planet look bigger.
Saturn is further from the Sun, thus cooler, and therefore less compact.
Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less
dense.
E. Jupiter’s strong magnetic field constrains its size.
Page 3 of 9
18. Which of the following best describes the internal layering of Jupiter, from the center outward?
A. core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of
liquid hydrogen; layer of gaseous hydrogen; cloud layer
B. core of rock and metal; mantle of lower density rock; upper layer of gaseous hydrogen;
cloud layer
C. solid rock core; layer of solid metallic hydrogen; layer of pure liquid hydrogen; cloud layer
D. liquid core of hydrogen compounds; liquid hydrogen layer; metallic hydrogen layer;
gaseous hydrogen layer; cloud layer
E. core of metal, liquid hydrogen layer; metallic hydrogen layer; cloud layer
19. Why are the inner planets made of denser materials than the outer planets?
A. The Sun’s gravity pulled denser materials toward the inner part of the solar nebula, while
lighter gases escaped more easily.
B. Denser materials were heavier and sank to the center of the nebula.
C. In the inner part of the nebula only metals and rocks were able to condense because
of the high temperatures, whereas hydrogen compounds, although more abundant, were
only able to condense in the cooler outer regions.
D. When the solar nebula formed a disk, materials naturally segregated into bands, and
in our particular solar system the denser materials settled nearer the Sun while lighter
materials are found in the outer part.
E. In the beginning, when the protoplanetary disk was spinning faster, centrifugal forces
flung the lighter materials toward the outer parts of the solar nebula.
20. Which of the following does NOT heat a planet’s interior?
A. accretion B. differentiation C. radioactive decay D. convection
21. The radius of Mars is 3400 km. How much more quickly/slowly does the interior of Mars
cool off compared to the interior of Earth?
A.
B.
C.
D.
E.
Earth cools off 1.9 times faster than Mars
Mars cools off 1.9 times faster than Earth
Mars cools off 0.53 times faster than Earth
Mars cools off 3.6 times faster than Earth
Earth cools off at the same rate as Mars
22. What is true about the direction of comet tails?
A. Comet tails always point away from the Sun.
B. Comet tails point in random directions depending on their trajectory.
C. Comet tails point either toward or away from the Sun depending on their size.
D. Comet tails point perpendicular to the ecliptic plane.
E. Comet tails are only directly behind the comets in their trailing orbital paths.
Page 4 of 9
Figure 1: Radial velocity curves of a star with an exoplanet. Assume the star is the same in
each case.
23. Refer to Figure 1. Which exoplanet has the most eccentric orbit?
A.
B.
C.
D.
E.
Top left
Top Right
Bottom left
Bottom Right
Insufficient information
24. Refer to Figure 1. Which exoplanet is the closest to the star?
A.
B.
C.
D.
E.
Top left
Top Right
Bottom left
Bottom Right
Insufficient information
25. Refer to Figure 1. Which exoplanet has the highest density?
A.
B.
C.
D.
E.
Top left
Top Right
Bottom left
Bottom Right
Insufficient information
Page 5 of 9
26. What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
A. methane B. hydrogen C. water D. ammonia
27. Why did Mars suffer a run-away cooling effect?
A. It is too far from the Sun for surface temperatures to remain above freezing.
B. It lacked enough carbon dioxide gas at its formation to sustain a greenhouse effect.
C. Mars is too small and cold inside for plate tectonics and outgassing to reclaim carbon
dioxide locked up in rocks, so it has no carbon cycle.
D. Mars has no magnetic field, so solar winds destroyed greenhouse gas molecules early in
its history.
28. At roughly what surface temperature would Earth eventually lose its atmosphere to thermal
escape from the exosphere? Assume the atmosphere is composed of nitrogen atoms, with a
mass of 2.3 × 10−26 kg. The escape velocity of Earth is roughly 11000 m/s.
A.
B.
C.
D.
E.
4K
40 K
400 K
4000 K
4e6 K
29. Which two properties are most important in determining the surface temperature of a
planet?
A.
B.
C.
D.
E.
internal temperature and distance from the Sun
size and distance from the Sun
size and atmosphere
internal temperature and atmosphere
distance from the Sun and atmosphere
30. Which of the following best describes how the greenhouse effect works?
A. Greenhouse gases absorb X-rays and ultraviolet light from the Sun, and this absorbed
radiation then heats the atmosphere and the surface.
B. A planet’s surface absorbs visible sunlight and returns this absorbed energy to space as
infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby
heats the lower atmosphere.
C. Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight
heats the lower atmosphere and the surface.
D. The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light and
thereby makes the atmosphere much hotter than it would be otherwise.
E. A good answer cannot be provided because we do not fully understand how it works.
Page 6 of 9
31. Suppose Earth’s atmosphere had no greenhouse gases whatsoever. Then Earth’s average
surface temperature would be (reflectivity = 29%) . . .
A.
B.
C.
D.
E.
...
...
...
...
...
257
265
273
281
288
K,
K,
K,
K,
K,
which is well below freezing.
which is slightly below freezing.
or about the freezing point for water.
or about a bit below what it is now.
or about the same as it is now.
32. How did the lunar maria form?
A. Large impacts fractured the Moon’s lithosphere, allowing lava to fill the impact basins.
B. The early bombardment created heat that melted the lunar surface in the regions of the
maria.
C. Volatiles escaping from the Moon’s interior heated and eroded the surface in the regions
of the maria.
D. The giant impact that created the Moon left smooth areas that we call the maria.
E. The maria are the result of gradual erosion by micrometeorites striking the Moon.
33. Which of the following moons is considered likely to have a deep, subsurface ocean of liquid
water?
A. Europa B. Io C. Titan D. Triton E. Callisto
34. What drives the motion of the tectonic plates on Earth?
A. Convection cells in the mantle B. Lava flows in trenches along the sea floor
centrifugal force D. Earth’s magnetic field E. Tidal forces from the Moon.
Page 7 of 9
C. The
(This page intentionally blank as scratch paper)
Page 8 of 9
Formulae
GM
R
KE = (1/2)mv 2
r
2kB T
vthermal =
m
r
2GM
vesc =
R
c = λf
d
t
s
θ=
d
Ug =
v=
dpc =
1
parcsec
c
a
dp = a(1−e)
e=
da = a(1+e)
E = hf
E
L=
t
L
B=
4πd2
p2yr = a3AU
F = ma
GM1 M2
Fg =
d2
light gathering power = πD2 /4
momentum = m v
angular momenutum = m v r
F = σT 4 =
L
A
vr
λobs − λrest
=
c
λrest
θ = 1.22
λ
D
E = mc2
P = nkB T
p2 =
4π 2
a3
G(M1 + M2 )
2.9 × 106 K nm
λmax
surface area
rate of planet cooling ∝
volume
r
4 (1 − r)
T“no greenhouse” = 280 K ×
d2
T =
Constants and Conversions
c = 3.00×108 m/s
me = 9.11×10−31 kg
LSun = 3.84×1026 W
kg m2
1J=1
s2
MEarth = 5.97×1024 kg
h = 6.63×10−34 J s
Watt
σ = 5.67×10−8 2 4
mK
−23
kB = 1.38×10
J/K
1 W = 1 J/s
1 AU = 1.50×1011 m
1 eV = 1.60×10−19 J
1 ly = 9.46×1015 m
MSun = 1.99×1030 kg
1 pc = 3.26 ly
mp = 1.67×10−27 kg
RSun = 696000 km
K = ◦ C+273
G = 6.67×10−11
m3
kg s2
Page 9 of 9
REarth = 6378 km