Midterm #2
Astronomy 100 – Prof. Vahé Peroomian
Fall Semester 2018 – October 18, 2018
Each of the 50 questions is worth 2 points. Please use the Scantron for your answers.
These sheets will NOT be graded.
1) Rank the five terrestrial worlds in order of size from smallest to largest.
A) Mercury, Venus, Earth, Moon, Mars
B) Mercury, Moon, Venus, Earth, Mars
C) Moon, Mercury, Venus, Earth, Mars
D) Moon, Mercury, Mars, Venus, Earth
E) Mercury, Moon, Mars, Earth, Venus
2) The lithosphere of a planet is the layer that consists of
A) material above the crust.
B) material between the mantle and the core.
C) the rigid rocky material of the crust and uppermost portion of the mantle.
D) the softer rocky material of the mantle.
E) the lava that comes out of volcanoes.
3) The terrestrial planet cores contain mostly metal because
A) the entire planets are made mostly of metal.
B) metals condensed first in the solar nebula and the rocks then accreted around them.
C) metals sank to the center during a time when the interiors were molten throughout.
D) radioactivity created metals in the core from the decay of uranium.
E) convection carried the metals to the core.
4) The two principal sources for the internal heating of terrestrial planets are
A) convection and accretion.
B) accretion and radioactivity.
C) accretion and eruption.
D) convection and radioactivity.
E) radiation and convection.
5) Why does Earth have the strongest magnetic field among the terrestrial worlds?
A) It is the only one that has both a molten metallic outer core and reasonably rapid rotation.
B) It is the only one that has a molten metallic outer core.
C) It rotates much faster than any other terrestrial world.
D) It is by far the largest terrestrial world.
E) It is the most volcanically active world.
6) Approximately how large is an impact crater compared to the size of the impactor?
A) the same size
B) 10-20 percent larger
C) 10 times larger
D) 100 times larger
E) 1,000 times larger
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7) Why do most scientists accept the claim that climate change is being caused by human activity?
A) Levels of atmospheric carbon dioxide show a sharp increase since the industrial revolution.
B) Computer models correctly reproduce past climate variations.
C) Computer models that include the effects of human activity correctly predict the current trend of
increasing temperatures.
D) Computer models that do not include the effects of human activity do not correctly predict the
current trend of increasing temperatures.
E) all of the above
8) The lunar maria (seas) were formed by ____________________
A) Wind erosion
B) Water erosion
C) The late heavy bombardment of the inner solar system
D) Extensive volcanic lava flows in the first billion years of the solar system
E) The long-term bombardment by meteorites of all sizes
9) Which of the following best describes tectonics?
A) the disruption of a planet's lithosphere by internal stresses
B) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
C) the eruption of molten rock from a planet's interior to its surface
D) the wearing down or building up of geological features by wind, water, ice, and other phenomena
of planetary weather
10) What are greenhouse gases?
A) gases that absorb visible light
B) gases that absorb infrared light
C) gases that absorb ultraviolet light
D) gases that transmit visible light
E) gases that transmit infrared light
11) Which of the following can act like a long-term "thermostat" for the Earth's average temperature?
A) radioactive elements trapped in the Earth's mantle
B) heat stored in the Earth's magnetosphere
C) heat stored in the Earth's liquid core
D) the carbon dioxide cycle
12) How does Earth's magnetosphere affect our atmosphere?
A) It deflects solar wind particles that would otherwise strip away the atmosphere.
B) It scatters the shorter wavelengths of light from the sun and causes the sky to be blue.
C) It produces chemical reactions that cause ozone to form in the upper atmosphere.
D) all of the above
13) The northern hemisphere of Mars has fewer craters than the southern hemisphere. This indicates that
A) geologic processes have resurfaced much of the northern hemisphere.
B) the northern hemisphere did not experience as many impacts.
C) volcanoes were more common in the southern hemisphere.
D) oceans of water once covered the southern hemisphere.
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14) Which feature in this photo of the full moon is one of the lunar maria?
A) 1
B) 2
C) 3
D) 4
E) 5
15) Why is Saturn almost as big as Jupiter, despite its smaller mass?
A) Saturn's rings make the planet look bigger.
B) Jupiter's greater mass compresses it more and increases its density.
C) Saturn is further from the Sun, thus cooler, and therefore less
compact.
D) 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.
16) Why does Jupiter have several distinct cloud layers?
A) Different layers represent clouds made of gases that condense at different temperatures.
B) Different layers represent the various regions where the temperature is cool enough for liquid
water to condense.
C) Different gases are present at different altitudes in Jupiter's atmosphere.
D) Winds prevent clouds from forming at some altitudes, so we see clouds only at the other
altitudes.
E) Clouds form randomly, so on average there are always several layers.
17) Which moon did the Huygens spacecraft land on?
A) Ganymede
B) Callisto
C) Europa
D) Titan
E) Triton
18) Which of the following best describes the composition of the particles forming Saturn's rings?
A) metallic grains
B) methane ice
C) water ice
D) volcanic rock
E) hydrogen and helium
19) Why do Uranus and Neptune appear blue?
A) Oceans that are visible through their atmospheres are blue.
B) The nitrogen gas in their atmospheres absorbs all colors except blue.
C) The methane gas in their atmospheres absorbs all colors except blue.
D) Small dust grains preferentially scatter blue light.
20) What is the Great Red Spot?
A) a long-lived, high-pressure storm on Jupiter
B) a hurricane that comes and goes on Jupiter
C) a place where reddish particles from Io impact Jupiter's surface
D) a region on Jupiter where the temperature is so high that the gas glows with red visible light
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21) Which statement about planetary rings is not true?
A) All four jovian planets have rings.
B) Saturn's rings formed along with its moons 4.6 billion years ago.
C) Individual ring particles orbit their planet in accord with Kepler's laws, so that particles closer in
orbit faster than particles farther out.
D) Rings are always located closer to a planet's surface than any large moons.
22) Why is Mars red?
A) It is made primarily of red clay.
B) Its surface rocks were rusted by oxygen.
C) Its atmosphere scatters blue light more effectively than red light.
D) Its surface is made of ices that absorb blue light.
E) Its surface is made of ices that absorb red light.
23) The seasonal polar caps which appear and disappear with the seasons on Mars are made of
A) water ice
B) methane ice
C) carbon dioxide ice
D) a uniform mixture of water and carbon dioxide ices
24) Spectra of the Martian surface taken from orbiting spacecraft have detected the presence of which of
the following minerals that form in water?
A) hydrated clays, sulfates and silicates
B) limestones
C) zircons
D) sea and rock salts
25) Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term
misleading?
A) The materials they are made of are more solid than gaseous.
B) They are not in any sense "giants."
C) They actually contain relatively little material in a gaseous state.
D) Actually, it's a great description, because these worlds are big and gaseous throughout.
26) Which of the following does not lend support to the idea that Pluto is a Kuiper-belt object?
A) Pluto has a comet-like composition and density.
B) Pluto is smaller than many known comets, such as Halley's comet.
C) Some Kuiper-belt objects have their own moons.
D) Pluto has a more eccentric orbit than other planets.
E) Some known Kuiper-belt objects are hundreds of kilometers across.
27) How can primitive meteorites be distinguished from processed meteorites?
A) Radiometric dating shows that primitive meteorites are slightly older.
B) Radiometric dating shows that primitive meteorites are slightly younger.
C) Primitive meteorites always contain iron and processed meteorites do not.
D) Primitive meteorites always contain rocky material and processed meteorites do not.
E) Primitive meteorites always contain carbon compounds and processed meteorites do not.
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28) Each white dot in the figure on the right represents the location of a
small body in our solar system. The donut shaped ring of white dots
just beyond Neptune's orbit represents the part of our solar system that
we call ____________________
A) the asteroid belt
B) the Kuiper belt
C) the Oort cloud
D) the solar nebula
29) Why does the plasma tail of a comet always point away from the Sun?
A) Radiation pressure from the Sun's light pushes the ions away.
B) The conservation of the angular momentum of the tail keeps it
always pointing away from the Sun.
C) Gases from the comet, heated by the Sun, push the tail away from
the Sun.
D) The solar wind pushes the plasma ions directly away from the Sun.
E) The particles in the plasma tail are more massive than those in the dust tail.
30) Will Pluto eventually collide with Neptune?
A) No, because Pluto's orbit is completely outside Neptune's orbit.
B) No, because Pluto's orbit is completely inside Neptune's orbit.
C) No, because Pluto's orbit never comes anywhere close to Neptune's orbit.
D) No, because the two planets have an orbital resonance that prevents them from colliding.
E) Yes.
31) According to the nebular theory, how did the asteroid belt form?
A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to
form the solar nebula.
B) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
C) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a
planet.
D) It consists of objects that fragmented from the protosun during a catastrophic collision early in
the formation of the solar system.
E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by
encounters with the jovian planets.
32) Why is the asteroid Ceres now considered to be a dwarf planet?
A) It is large enough to be round.
B) It is made mostly of rock.
C) It is larger than Pluto.
D) It orbits inside the frost line.
33) What is a so-called "hot Jupiter"?
A) a planet with a mass similar to Jupiter but composition similar to Mercury
B) a planet with a mass and composition similar to what we would expect if Jupiter were hotter
C) a Jupiter mass planet orbiting a star that is more massive and hotter than the Sun
D) a planet with a mass similar to Jupiter but very close to the central star and therefore hot
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34) What is the chief difficulty in attempting to detect planets around other stars?
A) Even the largest planets are thousands of times smaller than their host stars.
B) Planets do not emit visible light, and they are typically at least a billion times fainter than their
host stars.
C) Planets do not glow in the infrared, so infrared telescopes cannot be used to study them, either.
D) As viewed from Earth, planets often hide behind their stars and cannot be seen.
E) all of the above
35) Which of the following methods has led to the most discoveries of extrasolar planet candidates?
A) detecting the infrared light emitted by the planet
B) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the
star's spectrum
C) detecting the dip in measured brightness as the planet crosses our line of sight to the star
D) detecting the shift of the star's position against the sky due to the planet's gravitational pull
E) detecting a planet ejected from a binary star system
36) What must be true about the orbit of a planet discovered by the transit method?
A) The planet must be closer to its star than Mercury is to the Sun.
B) As seen from Earth, the planet's orbit must be nearly perpendicular to our line of sight.
C) As seen from Earth, the planet's orbit must be nearly parallel to our line of sight.
D) The planet's orbit must be very close to circular.
E) The planet's orbit must be very eccentric.
37) Using the transit method, how many times must a dip in the brightness of a star be observed before it
can qualify as an actual planet detection?
A) 1 time
B) 2 times
C) 3 times
D) 4 times
E) 5 times
38) What field of science are the experiments on the Mars Rovers Sojourner, Spirit, Opportunity and
Curiosity most closely related to?
A) physics
B) geology
C) biology
D) astronomy
E) chemistry
39) Which new idea has been added into our theory of solar system formation as a result of the
discoveries of extrasolar planets?
A) Planets can migrate from the orbits in which they are born.
B) In addition to the categories of terrestrial and jovian, there must be an "in-between" category of
planet that has the mass of a jovian planet but the composition of a terrestrial planet.
C) In some star systems, it is possible for jovian planets to form in the inner solar system and
terrestrial planets to form in the outer solar system.
D) Some of the "exceptions to the rules" in our own solar system are likely to have been the result of
giant impacts.
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40) Which of the following statements is an overall summary of the findings from the Viking biology
experiments on Mars?
A) the Martian soil showed no signs of chemical or biological activity
B) the Martian soil showed clear signs of biological activity
C) the Martian soil is chemically reactive but shows no signs of biological activity
D) the Martian soil contained organic molecules but showed no signs of biological activity
41) The process of making an uninhabitable planet like Mars habitable and suitable for humans is
referred to as
A) bioforming
B) bioadaptation
C) terra-restructuring
D) terraforming
42) You observe a star very similar to our own Sun in size and mass. This star moves very slightly back
and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting
planet. What can you conclude about the orbiting planet?
A) The planet must be closer to the star than Earth is to the Sun.
B) The planet must have a mass about the same as the mass of Jupiter.
C) The planet must be farther from the star than Neptune is from the Sun.
D) You do not have enough information to say anything at all about the planet.
43) The diagram on the right shows the orbital path of the Sun
around the center of mass of our solar system as it would
appear from a distance of 30 light-years for the period
1960–2025. If aliens had constructed this graph at their
home star system, they could learn all of the
following except
A) the fact that the Sun has more than two planets
B) the mass and orbital period of Jupiter
C) the orbital distance of Saturn
D) the fact that large, icy objects orbit the Sun in the
Kuiper belt
44) What is the main reason that Mars, compared to Earth,
has become so geologically inactive?
A) its size
B) its distance from the Sun
C) its composition
D) its tilt
E) its rotation rate
45) What is the origin of Martian meteorites?
A) they are rocks brought to Earth by Martians
B) they are rocks brought back to Earth by sample return missions
C) they are rocks blasted from the surface of Mars by volcanoes; these rocks then floated around in
interplanetary space before falling to Earth
D) they are rocks blasted from the surface of Mars by impacts; these rocks then floated around in
interplanetary space before falling to Earth
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46) Which of the following methods has been the LEAST successful in detecting extrasolar planets
around other star systems?
A) regular changes in the positions of the parent stars with respect to more distant stars as they move
across the sky
B) detection of Doppler shifts in the spectra of the parent stars
C) detection of brightness changes in a star as a planet passes in front of it
D) detection of reflected starlight
47) In an extrasolar planetary system containing a single planet, the parent star is measured to move
about its center of mass every 24 years. Given this, what is the orbital period of the planet?
A) 12 years
B) 24 years
C) 48 years
D) this cannot be determined from this observation
48) Where is Jupiter's strong magnetic field generated?
A) rocky core
B) metallic hydrogen layer
C) liquid hydrogen layer
D) gaseous hydrogen layer
E) cloud tops
49) According to current understanding, which of the following is required for a planet to have rings that
last for a very long time?
A) The planet must have many small moons that orbit relatively close to the planet in its equatorial
plane.
B) The planet must be at least as massive as Saturn.
C) The planet must orbit its star at a distance greater than Mars orbits the Sun.
D) The planet must once have had a large moon that came too close to it, shattering the moon and
creating the ring particles.
50) The graph shows how a star's orbital speed (radial velocity)
varies with time due to the gravitational tug of an orbiting
planet. The amplitude of the radial velocity (how high and
how low the radial velocity gets to be) is related to the
planet’s
A) orbital shape
B) orbital period
C) mass
D) radius
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