ASTRONOMY 121 ANSWERS – version A
Exam I
January 20, 2005
Prof. J. E. Brau
1. Kepler's
1st Law states Planetary orbits are
a. ellipses with the Sun at one focus
2.
Kepler's third law of planetary motion states that a planet in orbit
around the Sun
will
e. have its orbital period squared
proportional to semi-major axis cubed.
3.
Kepler's Laws follow from
c.
4.
An astronomical unit (AU) is
b. 150,000,000 km (93,000,000 miles)
5.
Which of the following are the terrestrial planets?
d. Mercury, Venus, Earth, Mars
6.
Which of the following are the jovian planets?
c. Jupiter, Saturn, Uranus, and Neptune
7. The
Earth's surface temperature is about:
c. 290 K
8. The least massive planets are the
d. Terrestrial planets
9.
The most massive planets are the
a. Jovian planets
10. The
average density of the three inner planets is
c. just over 5000 kg/m3
11.
Which of the following defines density?
b. mass divided by volume
12.
How do the densities of the
terrestrial and jovian planets compare?
e. The
terrestrial planets have higher densities than the jovian planets
13. One
of the following factors, along with temperature, determines whether a body
will retain an atmosphere of a given composition.
c. escape speed
14. The
internal structure of the Earth is determined from
a. propagation
of S and P waves
15. How
do the escape speeds of the jovian planets compare to the terrestrial planets?
a. The
jovian planets have much higher escape speeds
16.
Which of the following have an icy
composition?
c. comets
17. The
planet with the slowest period of rotation
b. Venus
18.
Where are the asteroids generally
found in the solar system?
b. between the orbits of Mars and Jupiter
19. Which
of the following is NOT a way in which the terrestrial and jovian planets
differ?
d. The jovian planets have orbits that are
highly inclined to the ecliptic and do
not
revolve in the same direction as the terrestrial planets
20.
The trapping of heat (infrared) radiation by a planetary atmosphere is
called the ____.
c. Greenhouse effect
21. A
"stretching" produced on one object by the gravity of another object,
the direct result of the dependence of the gravitational force on distance, is
termed a ____________.
b. tidal effect
22. The
_______ are two regions of charged particles trapped in the magnetosphere of
the Earth.
d. Van
Allen belts
23. The
Sun contains
d. about 99.8% of the mass of the Solar
System
24. Which
of the following statements is true regarding spacecraft trajectories near
planets at orbital speeds above the escape velocity?
c. The spacecraft can either gain or lose
orbital speed during the encounter
depending
on the exact orbit.
25.
Which of the following is NOT a
characteristic that is true of terrestrial planets?
d. Lower density than jovian planets..
26. Which
of the following is NOT a characteristic that is true of jovian planets?
d. Jovian planets have weak magnetic fields.
27. The
force of gravity between two objects obeys which of the following
relationships?
.
e. It is attractive and increases if their
masses increase.
28. Kepler's
second law of planetary motion states that a planet in orbit around the sun
will do which of the following?
c. Sweep out equal areas in equal times.
29.
What is the name given to the
phenomenon in which the apparent motion of planets sometimes reverses?
d. Retrograde motion.
30.
What is the trend of the spacing between orbits of the planets as we
move outward from the Sun.
c. the orbits are more widely spaced the
farther from the Sun
31.
e. 165 Earth years.
32. What
is the primary ingredient in the Earth's atmosphere?
a. Nitrogen
33. The
Earth's greenhouse effect
b. keeps the surface warmer than it would be
otherwise
34.
What characteristic of the Earth
is most responsible for the northern lights (
b. Earth's magnetic field
35. The
sky is blue for the following reason
c. Blue light from the Sun is scattered more
than red light by the atmosphere
36.
When an Earth scientist says that the Earth is
"differentiated," she means that:
a. The ground beneath our feet gets hotter and denser as you go
inward
37. The
oldest rocks on Earth are dated to be:
b. Nearly 4 billion years old
38. When
two tectonic plates collide:
c. They do not stop moving, but produce large deformation of
various types
39.
Name two places on Earth where convection
is operating on a large scale, creating natural phenomena that are important
features for life on Earth.
a. In the atmosphere and the mantle
40.
Which of the following objects
produces most of the tidal effect on Earth?
d.
The Moon
41. What
is the best description for the history of the Earth's rotation?
b. It is very gradually slowing down
42.
Which of the following regions of
the Earth appears to be unique to it (such a region is not found on any other
body in the solar system)?
b. hydrosphere
43. When
expressed in Kelvin, what is 100 degrees Centigrade?
d. 373 K
44. Absolute
Zero is
c. 0 Kelvin
45.
The speed of light is
c.
300,000 kilometers per second
46. The
heliocentric model of the Solar System was developed by
a. Nicholas Copernicus
47.
The presence of a magnetic field
is a good indication that:
b. A
quantity of liquid metal is swirling around in the Earth's core
48. The
semi-major axis of a planet's orbit
b. tells us the planet's approximate distance
from the Sun
49. The
only planet which has not been visited by spacecraft is
e. Pluto
50. An
inverse-square force has the following property
b. It weakens with increased distances from
the source
51. The
Sun's inward pull of gravity on a planet competes with what tendency of a
planet to cause the planet to follow an elliptical orbit
a. The planet's tendency to continue moving in a straight line
52. Density
is a convenient measure of what property of a planet
a. Its compactness
53. On
which of the following planets have spacecraft landed?
a. Mars
54. Which
of the following can be found among the Solar System's interplanetary debris
a. asteroids, comets, and meteoroids
55. Which
of the following elements was NOT very common in the Earth's atmosphere, just
after the Earth formed?
d. oxygen
56. What
method is used to date old rocks found on Earth?
a. radioactive dating
57.
The North American and Pacific
plates are rubbing past each other, causing
d.
58.
What energy boost did the Voyager
missions use in their mission to the outer planets
a. Jupiter's gravity
59.
Which region of the Earth has the
highest density?
b. core
60.
Which of the following statements
is true
a. All of the planets of the Solar System orbit the Sun
counterclockwise as seen
from
above the Earth's North Pole
61.
Relative to the Earth's core,
Mercury's core
a. is a larger fraction of the planet's volume
62. A
spin-orbit resonance is
a. the condition in which a body's rotation is
simply related to its orbital period
63. Mercury
is marked by
a.
a rich system of planetary rings
b.
two small moons
c.
an atmosphere dominated by C02
xxxx d. none
of above
64. The
semi-major axis of Mercury measures
d. 0.38 AU
65. The
Huygens probe now rests on the surface of
d. Titan
66. Most
of the craters on the Moon are thought to have been formed by __________.
a. meteoritic impacts
67. The
Moon has no atmosphere because it has ________.
b. weak gravity
68. The
____________ are huge, dark, lava-filled regions of the Moon.
a. maria
69. The
layer of dust and other debris on the lunar surface is the cumulative result of
______________ over many years.
a. micrometeoritic impacts
70. The
only satellite in the solar system with an atmosphere is
b. Titan
71. The
planet Mercury is tidally locked to the Sun in the sense that it orbits twice
while it rotates _____________ times relative to the fixed stars.
a. three
72. The
magnetic field of Mercury is about _________
the strength of the magnetic field of Earth.
a. 1/100 times
73. In
visual appearance, Mercury appears nearly identical to the Moon, except that
Mercury lacks prominent ______________.
a. maria
74. The
far side of the Moon differs from the near side in
c. lacking maria
75. Mercury
appears in the sky:
c.
Just after sunset
d.
Just before sunrise
xxxx e. Either c or d
76. What
force on the Moon causes it to keep a single hemisphere pointed toward Earth?
b. Tidal force
77. The
Moon's atmosphere is composed mostly of:
e. It has no atmosphere
78. The
average rate of erosion on the Moon is far less than that on the Earth because:
b. The Moon lacks wind and running water
79. What
theory of the Moon's origin is favored by most astronomers today?
d.
The Moon originated as material torn
from Earth by the collision of a large
Mars-sized
body
80. Mercury's
surface most resembles that of what other body?
b. The Moon
81. Mercury
experiences extreme highs and lows in temperature between day and night
because:
b. Mercury lacks a blanket of atmosphere
82. Mercury's
0 degree inclination is explained by
d. Tidal forces from the Sun
83. Mercury's
orbit around the Sun is characterized by
a. A highly eccentric, elliptical orbit
84. The
average density of the Moon is
b. just over 3000 kg/m3
SHORT QUESTIONS
87.
What is the most massive planet?
Jupiter
88.
Which planet has the lowest density?
Saturn
89.
Which planet has the most moons?
Jupiter
90.
Jupiter's orbit has a semi-major axis of 5.5 astronomical units (or 820
x 106 km).
Calculate
the time it takes light to travel from the Sun to Jupiter.
820
x 106 km/300 x 103 km/sec = 8200/3 seconds = 2733 seconds
= 45.5 minutes
91. What
is the age of the Earth and the Solar System?
4.6
billion years
92. Galileo
discovered the first moons of the solar system, beyond the Earth’s moon. Which planet’s moons were these?
Jupiter
93. Name
the event during which the Moon passes directly between the Earth and the Sun,
temporarily blocking the Sun's light.
(Hint: this is a two word answer)
Solar
Eclipse
94. What
planet has the highest surface temperature?
Venus (Mercury is slightly cooler, but is an
acceptable answer)
95. What
planet is locked in a 3:2 spin-orbit resonance?
Mercury