2) Suppose you view the solar system from high above Earth’s North Pole. Which of the
following statements about planetary orbits will be true?
A) All the planets orbit counterclockwise around the Sun.
B) The inner planets orbit the Sun counterclockwise while the outer planets orbit the Sun
clockwise.
C) All the planets except Uranus orbit the Sun counterclockwise; Uranus orbits in the opposite
direction.
D) The inner planets orbit the Sun clockwise while the outer planets orbit the Sun
counterclockwise.
3) Which of the following statements about our Sun is not true?
A) The Sun’s diameter is about 5 times that of Earth.
B) The Sun is a star.
C) The Sun contains more than 99% of all the mass in our solar system.
D) The Sun is made mostly of hydrogen and helium.
4) Which of the following is not true of Mercury?
A) It has no moons.
B) At any given time, about half the planet is colder than Antarctica.
C) Its surface is heavily cratered.
D) Mercury has a density greater than that of Earth.
5) Which of the following statements about Mars is not true?
A) We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks.
B) We have landed spacecraft on its surface.
C) It is considered part of our inner solar system.
D) It is frozen today, but once had flowing water.
6) The planet in our solar system with the highest average surface temperature is ________.
A) Venus
B) Mercury
C) Earth
D) Neptune
7) The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium.
According to modern science, where did these elements come from?
A) They were produced by stars that lived and died before our solar system was born.
B) They were produced in the core of the Sun.
C) They have been present in the universe since its birth.
D) They were made by chemical reactions in interstellar gas.
8) Which of the following statements does not apply to the formation of gas giants like Jupiter,
compared to terrestrial planets?
A) caused icy planetesimals to slingshot away from the Sun, to become Oort cloud comets
B) formed in a region with lower orbital speeds
C) accreted from icy planetesimals
D) surface dramatically altered during bombardment
E) formed in regions cold enough for water to freeze
9) Which jovian planet does not have rings?
A) Jupiter
B) Neptune
C) Uranus
D) Mars
E) All the jovian planets have rings.
10) Which moons are sometimes called the Galilean moons?
A) the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto
B) the two largest moons in the solar system: Ganymede and Titan
C) the moons that orbit their planet “backward” compared to their planet’s rotation, such as
Neptune’s moon Triton
D) the moons orbiting Uranus, which was once named “planet Galileo”
11) The Cassini mission to Saturn consists of ________.
A) an orbiter that orbits Saturn and a probe that descended to the surface of Titan
B) a large spacecraft that flew by Saturn on its way to other planets
C) an orbiter that orbits Saturn and a probe that descended into Saturn’s atmosphere
D) a spacecraft that orbits Saturn and a sample return mission that landed on Titan, scooped up a
surface sample, and will return it to Earth
12) Which planet (besides Earth) has been visited by the largest number of robotic spacecraft?
A) Mars
B) Jupiter
C) Venus
D) Saturn
13) When we say that jovian planets contain significant amounts of hydrogen compounds, we
mean all the following chemical compounds except ________.
A) carbon dioxide
B) water
C) ammonia
D) methane
14) In essence, the solar nebular theory states that ________.
A) our solar system formed from the collapse of an interstellar cloud of gas and dust
B) nebulae are clouds of gas and dust in space
C) the planets each formed from the collapse of its own separate nebula
D) The nebular theory is a discarded idea that imagined planets forming as a result of a near-
collision between our Sun and another star.
15) Based on studies of the composition of stars and interstellar gas clouds, what was the
approximate chemical composition of the solar nebula?
A) 98% hydrogen and helium, 2% everything else
B) 50% hydrogen and helium, 50% everything else
C) 98% hydrogen, 2% helium
D) roughly equal proportions of hydrogen, helium, water, and methane
16) Why would we expect to find a higher percentage of heavy elements in a young star, as
opposed to an older star?
A) Heavy elements are produced by stars living and dying, so more heavy elements get
incorporated into future generations of stars.
B) Heavy elements are destroyed by stars as they age.
C) Heavy elements were more common long ago before stars began forming.
D) Light elements are the result of heavy elements decaying over time.
17) According to our theory of solar system formation, what three major changes occurred in the
solar nebula as it shrank in size?
A) It got hotter, its rate of rotation increased, and it flattened into a disk.
B) Its mass, temperature, and density all increased.
C) It gained energy, it gained angular momentum, and it flattened into a disk.
D) Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to
make the jovian planets, and central temperatures rose to more than a trillion Kelvin.
18) Which of the following types of material can condense into what we call ice at low
temperatures?
A) hydrogen compounds
B) hydrogen and helium
C) rock
D) metal
19) According to our present theory of solar system formation, which of the following lists the
major ingredients of the solar nebula in order from the most abundant to the least abundant?
A) hydrogen and helium gas; hydrogen compounds; rock; metal
B) hydrogen compounds; hydrogen and helium gas; metal; rock
C) hydrogen and helium gas; rock; metal; hydrogen compounds
D) hydrogen; water; methane; helium
20) What do we mean by the frost line when we discuss the formation of planets in the solar
nebula?
A) It is a circle at a particular distance from the Sun, beyond which the temperature was low
enough for ices to condense.
B) It is another way of stating the temperature at which water freezes into ice.
C) It marks the special distance from the Sun at which hydrogen compounds become abundant;
closer to the Sun, there are no hydrogen compounds.
D) It is the altitude in a planet’s atmosphere at which snow can form.
21) What do we mean by accretion in the context of planet formation?
A) the growth of planetesimals from smaller solid particles that collided and stuck together
B) the formation of moons around planets
C) the solidification of ices, rocks, and metal from the gas of the solar nebular
D) the growth of the Sun as the density of gas increased in the center of the solar nebula
22) According to our theory of solar system formation, what are asteroids and comets?
A) leftover planetesimals that never accreted into planets
B) the shattered remains of collisions between planets
C) chunks of rock or ice that condensed after the planets and moons finished forming
D) chunks of rock or ice that were expelled from planets by volcanoes
23) What do we mean by the period of heavy bombardment in the context of the history of our
solar system?
A) the first few hundred million years after the planets formed, which is when most impact
craters were formed
B) the time before planetesimals finished accreting into planets, during which many growing
planetesimals must have shattered in collisions
C) the time during which heavy elements condensed into rock and metal in the solar nebula
D) the period about 65 million years ago when an impact is thought to have led to the extinction
of the dinosaurs
24) What is the giant impact hypothesis for the origin of the Moon?
A) The Moon formed from material blasted out of the Earth’s mantle and crust by the impact of a
Mars-size object.
B) The Moon formed when two gigantic asteroids collided with one another.
C) The Moon originally was about the same size as Earth, but a giant impact blasted most of it
away so that it ended up much smaller than Earth.
D) The Moon formed just like the Earth, from accretion in the solar nebula.
25) Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years.
Which of the following statements will be true after 20 years pass?
A) You’ll have 0.25 kilogram of the radioactive substance remaining.
B) All the material will have completely decayed.
C) You’ll have 0.75 kilogram of the radioactive substance remaining.
D) You’ll have 0.5 kilogram of the radioactive substance remaining.
26) According to modern scientific dating techniques, approximately how old is the solar
system?
A) 4.5 billion years
B) 10,000 years
C) 4.6 million years
D) 14 billion years
6.6 Mastering Astronomy Concept Quiz
1) Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is
________.
A) much larger
B) about the same
C) much smaller
D) just slightly less
2) How is Einstein’s famous equation, E = mc2, important in understanding the Sun?
A) The Sun has a magnetic field strong enough to influence the atmospheres of the planets.
B) The Sun’s surface temperature is about 6,000° Celsius.
C) The Sun generates its energy by converting 4 million tons of mass to energy each second.
D) This equation represents how difficult science is, so understanding the Sun is difficult as well.
3) In what way is Venus most similar to Earth?
A) Both planets are nearly the same size.
B) Both planets have very similar atmospheres.
C) Both planets have similar surface geology.
D) Both planets have warm days and cool nights.
4) Which of the following observations of an extrasolar planet system would be inconsistent with
the nebular theory of planet formation?
A) a system in which some planets have small moons orbiting in a direction opposite to the
planet’s rotation
B) a system which has two terrestrial planets close in and two gas giants farther out
C) a system in which the planets rotate in the same direction as they orbit
D) a system in which all the planets orbit in completely different planes
5) Which of the following statements about the recently-discovered object Eris is not true?
A) It is thought to be the first example ever discovered of a new class of objects.
B) It has at least one moon.
C) It lies well beyond Pluto and Neptune.
D) It orbits the Sun in the same direction as the other planets.
6) Mars has two moons that are most similar in character to ________.
A) small asteroids
B) comets
C) Earth’s Moon
D) particles in the rings of Saturn
7) Considering only the tilt of their axis, which planet listed below would have the most extreme
seasons?
A) Uranus
B) Mars
C) Earth
D) Jupiter
8) In what way is Pluto more like a comet than a planet?
A) It is made mostly of rock and ice.
B) It sometimes enters the inner solar system.
C) It has a long tail.
D) It has a moon.
9) Which of the following is not a major pattern of motion in the solar system?
A) Nearly all comets orbit the Sun in the same direction and roughly the same plane.
B) Most of the solar system’s large moons orbit in their planet’s equatorial plane.
C) The Sun and most of the planets rotate in the same direction in which the planets orbit the
Sun.
D) All of the planets orbit the Sun in the same direction—counterclockwise as viewed from
above Earth’s north pole.
10) Which of the following is not a major difference between the terrestrial and jovian planets in
our solar system?
A) Terrestrial planets contain large quantities of ice, and jovian planets do not.
B) Terrestrial planets orbit much closer to the Sun than jovian planets.
C) Terrestrial planets are higher in average density than jovian planets.
D) Jovian planets have rings, and terrestrial planets do not.
11) The following statements are all true. Which one counts as an “exception to the rule” in
being unusual for our solar system?
A) Earth has a large moon.
B) Venus does not have a moon.
C) Jupiter has a very small axis tilt.
D) Saturn has no solid surface.
12) About 2% of our solar nebula consisted of elements heavier than hydrogen and helium.
However, the very first generation of stars in the universe probably consisted only of hydrogen
and helium. Which of the following statements is most likely to have been true about these first-
generation stars?
A) They likely had numerous terrestrial planets but no jovian planets.
B) The nebula in which they formed likely had more hydrogen compounds than the nebula that
formed the solar system.
C) They likely had even numbers of terrestrial and jovian planets, like our solar system.
D) Planets were likely very rare or non-existent around these first-generation stars.
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) the law of conservation of angular momentum
B) the law of conservation of energy
C) the law of universal gravitation
D) Einstein’s law E = mc2
14) According to our theory of solar system formation, which law best explains why the central
regions of the solar nebula got hotter as the nebula shrank in size?
A) the law of conservation of energy
B) the law of conservation of angular momentum
C) Newton’s third law
D) the two laws of thermal radiation
15) According to our present theory of solar system formation, which of the following best
explains why the solar nebula ended up with a disk shape as it collapsed?
A) It flattened as a natural consequence of collisions between particles in the nebula.
B) It was fairly flat to begin with, and retained this flat shape as it collapsed.
C) The force of gravity pulled the material downward into a flat disk.
D) The law of conservation of energy contributed to how a disk shape formed.
16) What is the primary reason we divide the ingredients of the solar nebula into four categories
(hydrogen/helium gas; hydrogen compound; rock; metal)?
A) The temperature at which these materials condense into a solid varies considerably.
B) The atomic mass number of these materials differs considerably.
C) The abundance of these materials depended on their location in the solar nebula.
D) The amount of energy required to ionize these materials varies considerably.
17) According to our present theory of solar system formation, which of the following statements
about the growth of terrestrial and jovian planets is not true?
A) The jovian planets began from planetesimals made only of ice, while the terrestrial planets
began from planetesimals made only of rock and metal.
B) Both types of planets began with planetesimals growing through the process of accretion, but
only the jovian planets were able to capture hydrogen and helium gas from the solar nebula.
C) Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian
planets but not around the growing terrestrial planets.
D) The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets
formed beyond it.
18) Many meteorites appear to have formed very early in the solar system’s history. How do
these meteorites support our theory about how the terrestrial planets formed?
A) The meteorites’ appearance and composition is just what we’d expect if metal and rock
condensed and accreted as our theory suggests.
B) The meteorites’ sizes are just what we’d expect if metal and rock condensed and accreted as
our theory suggests.
C) Their overall composition is just what we believe the composition of the solar nebula to have
been: mostly hydrogen and helium.
D) Their appearance and composition matches what we observe in comets today, suggesting that
they were once pieces of icy planetesimals.
19) Suppose the Sun had been born with less mass, making it a small, cooler star only able to
heat everything around it to a level one-half as hot as its current temperature. According to the
solar nebular theory, how would the formation of the solar system have been different?
A) Asteroids would have formed farther from the Sun.
B) Both terrestrial and jovian planets would have generally formed closer to the Sun.
C) There would be no comets.
D) There would be no terrestrial planet systems.
20) According to our present theory of solar system formation, how did Earth end up with
enough water to make oceans?
A) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit
of Mars.
B) The water was brought to the forming Earth by planetesimals that accreted near Earth’s orbit.
C) The water was formed by chemical reactions among the minerals in the Earth’s core.
D) Earth formed at a distance from the Sun at which liquid water happened to be plentiful in the
solar nebula.
21) According to our present theory of solar system formation, why were solid planetesimals
able to grow larger in the outer solar system than in the inner solar system?
A) because only metal and rock could condense in the inner solar system, while ice also
condensed in the outer solar system
B) because the Sun’s gravity was stronger in the outer solar system, allowing more solid material
to collect
C) because gas in the outer solar system contained a larger proportion of rock, metal, and
hydrogen compounds than the gas in the inner solar system
D) because only the outer planets captured hydrogen and helium gas from the solar nebula
22) According to our basic scenario of solar system formation, why do the jovian planets have
numerous large moons?
A) As the growing jovian planets captured gas from the solar nebula, the gas formed swirling
disks around them, and moons formed from condensation accretion within these disks.
B) Because of their strong gravity, the jovian planets were able to capture numerous asteroids
that happened to be passing nearby, and these became the major moons of the jovian planets.
C) The large moons of the jovian planets originally formed in the inner solar system, and these
moons then migrated out to join up with the jovian planets.
D) The many moons of the jovian planets remains one of the unexplained mysteries of the
formation of our solar system.
23) Which of the following is not evidence supporting the idea that our Moon formed as a result
of a giant impact?
A) The Pacific Ocean appears to be a large crater—probably the one made by the giant impact.
B) Computer simulations show that the Moon could really have formed in this way.
C) The Moon’s average density suggests it is made of rock much more like that of the Earth’s
outer layers than that of the Earth as a whole.
D) The Moon has a much smaller proportion of easily vaporized materials than Earth.
24) Why are terrestrial planets more dense than the jovian planets?
A) Only dense materials could condense in the inner solar nebula.
B) The Sun’s gravity pulled dense materials into the inner solar system.
C) Gravity compresses terrestrial planets to a higher degree, making them denser.
D) Since the jovian planets are more massive than the terrestrials, the jovians must be more
dense.
25) Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has
a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present
in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the
rock solidified. How old is the rock?
A) 3.75 billion years
B) 1.25 billion years
C) 2.5 billion years
D) 5.0 billion years
26) How do scientists determine the age of the solar system?
A) radiometric dating of meteorites
B) radiometric dating of Moon rocks
C) radiometric dating of the oldest Earth rocks
D) Theoretical calculations tell us how long it has taken the planets to evolve to their present
forms.
27) The region of our solar system between Mercury and Mars has very few asteroids, while the
region between Mars and Jupiter has many asteroids. Based on what you have learned, what is
the most likely explanation for the lack of asteroids between Mercury and Mars?
A) There were very few planetary leftovers in this region because most of the solid material was
accreted by the terrestrial planets as the planets formed.
B) It was too hot for asteroids to form in this part of the solar system.
C) Gravity was too weak to allow asteroids to form in this part of the solar system.
D) All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt
between Mars and Jupiter.
28) Based on everything you have learned about the formation of our solar system, which of the
following statements is probably not true?
A) Only a tiny percentage of stars are surrounded by spinning disks of gas during their
formation.
B) A star system’s planets generally tend to orbit their star in the same direction and
approximately the same plane.
C) Other solar systems will also have planets in the two basic categories of terrestrial and jovian.
D) Other planetary systems will have far more numerous asteroids and comets than actual
planets.