Astronomy
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma rays, X-rays, ultraviolet, visible light, infrared, radio
What are greenhouse gases?
gases that absorb infrared light
Some nitrogen atoms have seven neutrons and some have eight neutrons; these two forms of nitrogen are:
isotopes of each other.
Suppose a planet is discovered by the Doppler method and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.
its rotation period
Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?
its size
What is the main reason that Mars, compared to Earth, has become so geologically inactive?
its size
Which of the following is the main reason why Venus has so little wind erosion?
its slow rotation
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
its wavelength and energy
Plants and animals are
just two small branches of the diverse "tree of life" on Earth.
According to our theory of solar system formation, what are asteroids and comets?
leftover planetesimals that never accreted into planets
Which of the following best describes tectonics?
the disruption of a planet's lithosphere by internal stresses
The wavelength of a wave is
the distance between two adjacent peaks of the wave.
Which of the following does the solar nebular theory not predict?
the equal number of terrestrial and jovian planets
Which of the following best describes volcanism?
the eruption of molten rock from a planet's interior to its surface
Which of the following best describes impact cratering?
the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
When we analyze whether a world is a possible home to life, the key thing we look for is ________.
the existence of liquid water
In the Drake equation (Number of Civilizations = N HP × f life × f civ × f now), what do we mean by f now?
the fraction of planets with civilizations at the present time (as opposed to only in the past or future)
Which object is likely to be the coldest? The object whose light spectrum is brightest in the
infrared.
An atom that has fewer electrons than protons is called a(n) ________.
ion
A planet's density can be determined solely by observing it pass in front of its parent star. T or F
False
A spacecraft traveling through the asteroid belt has a high risk of being destroyed through a collision. T or F
False
All the planets in the solar system have at least one moon T or F
False
All the planets in the solar system rotate (spin) in the same direction as they orbit the Sun. T or F
False
Jupiter's Great Red Spot is a low-pressure storm, like a hurricane on Earth. T or F
False
The Huygens landing showed that the surface of Titan is made of mostly rock. T or F
False
Which of the following best describes convection?
It is the process in which warm material expands and rises while cool material contracts and falls.
What is unusual about Triton?
It orbits its planet backward.
Planets detected via the Doppler method have been mostly
Jupiter-mass, in very close orbits.
Which of the following is not a characteristic of the inner planets?
They have substantial atmospheres.
Which process(es) contribute(s) to the gradual evolution of life via natural selection?
(Organisms tend to produce more offspring than the local environment can support, Individuals in a population vary in many heritable traits, The competition for resources will favor those individuals in a population with traits that make them more competitive.) all of the above
What are scientists' best guess(es) for the requirement(s) of life?
(energy to fuel the activities of life, a source of materials (nutrients), liquid water) all of the above
What kind of surface features may result from tectonics?
(valleys, volcanos, cliffs, mountains) all of the above
Why is Mars red?
Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface.
Based on the model types shown in the figure above, a planet made almost entirely of hydrogen compounds would be considered a
"water world."
Which of the following are relatively unchanged fragments from the early period of planet building in the solar system?
(Asteroids, Kuiper belt comets, Oort cloud comets) all of the above
Which of the jovian planets have rings?
(Neptune, Uranus, Saturn, Jupiter) all of the above
What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium?
2 percent
About how old is the solar system?
4.5 billion years
One of the absorption lines of hydrogen has a rest wavelength of 656 nm (at rest means with respect to the observer, like in a lab). You observe several stars and measure the wavelength of this same hydrogen absorption line in each star. Based on the measured wavelength of this line, which star is moving towards the Earth the fastest?
630 nm
In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?
A massive planet that is close to its star
What do we mean by a "super Earth"?
A planet made of metal and rock that is larger in mass than Earth
What do we mean by a "hot Jupiter"?
A planet that is Jupiter-like in size but orbits very close to its star
What is an extrasolar planet?
A planet that orbits a star that is not our own Sun
Which of the following best describes how the greenhouse effect works?
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.
Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago?
Fossilized dinosaur bones contain fragments of rock from the impact.
How do the jovian planet interiors differ from one another?
All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium.
Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
All the planets orbit counterclockwise around the Sun
Which statement about photons of light is true?
An infrared photon has less energy than an X-ray photon, but travels at the same speed.
What must be true about the orbit of a planet discovered by the transit method?
As seen from Earth, the planet's orbit must be nearly parallel to our line of sight.
Why did the solar nebula heat up as it collapsed?
As the cloud shrank, its gravitational potential energy was converted to thermal energy.
How do asteroids differ from comets?
Asteroids are made mostly of rocky and/or metallic material. Comets are made mostly of icy material.
Why do asteroids and comets differ in composition?
Asteroids formed inside the frost line, while comets formed outside.
Based on current data, about what fraction of stars have one or more planets?
At least about 70%
The spectrum of Star A has an absorption line of hydrogen at 660.0 nm. The spectrum of Star B has an absorption line at 666 nm. The wavelength of this transition in the laboratory is 656.2 nm. What can I say about Star A and B?
Both stars are moving away from me, Star B is faster than Star A.
Why does the burning of fossil fuels increase the greenhouse effect on Earth?
Burning releases carbon dioxide into the atmosphere.
Suppose you are using the Doppler method to look for planets around another star. What must you do?
Compare many spectra of the star taken over a period of many months or years.
Which of the following will allow you to learn something about a transiting planet's atmospheric composition?
Compare spectra obtained before and during an eclipse.
Why does Jupiter have several distinct cloud layers?
Different layers represent clouds made of gases that condense at different temperatures.
Which of the following best describes the geological histories of the Moon and Mercury?
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
Which of the following is not a possible solution to the Fermi Paradox?
Given the current age of our galaxy, there has not been enough time for a galactic civilization to develop.
Why didn't a planet form where the asteroid belt is now located?
Gravitational tugs from Jupiter prevented material from collecting together to form a planet.
In the Drake equation, suppose that the term flife=12flife=12. What would this mean?
Half of the habitable worlds in the galaxy actually have life, while the other half don't.
What are the two primary methods by which planets have been found around other stars in our galaxy?I) Direct images in visible and infrared lightII) Indirectly by detecting the motion of the host starIII) Indirectly by measuring the drop in brightness of the host star when the planet crosses our line of sight
II and III
What is the primary reason an icy moon is likely to be more geologically active than a rocky moon of the same size?
Ice has a lower melting point than rock.
Which of the following might explain the lack of "water worlds"—small planets made mostly of water or other hydrogen compounds—in our own solar system?
In our solar system, the solar wind did not clear out gas until relatively late.
From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?
It causes the Sun to move in a small ellipse with an orbital period of about 12 years.
How does Earth's magnetosphere affect our atmosphere?
It deflects solar wind particles that would otherwise strip away the atmosphere.
Why did the solar nebula flatten into a disk?
It flattened as a natural consequence of collisions between particles in the nebula, changing random motions into more orderly ones.
According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?
It got hotter, its rate of rotation increased, and it flattened into a disk.
Why does Venus have such a large difference in temperature between its "no atmosphere" temperature and its actual temperature?
It has a large amount of carbon dioxide in its atmosphere.
Which of the following best describes how the Drake equation is useful?
It helps us understand what we need to know in order to determine the likelihood of finding other civilizations in our galaxy
What do we mean by the frost line when we discuss the formation of planets in the solar nebula?
It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.
How does the Sun's mass compare with that of the planets?
It is about a thousand times more massive than all the planets combined
According to the nebular theory, how did the Oort cloud form?
It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.
According to the nebular theory, how did the Kuiper belt form?
It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
Which of the following best describes natural selection?
It is the idea that organisms with genetic traits that improve their ability to reproduce are more likely to pass those traits on to future generations.
Which statement about Io is true?
It is the most volcanically active body in our solar system.
Why does Earth have the strongest magnetic field among the terrestrial worlds?
It is the only one that has both a molten metallic outer core and reasonably rapid rotation.
What's unusual about our Moon?
It's surprisingly large relative to the planet it orbits.
Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?
Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
Jovian planets can migrate from the orbits in which they are born.
Which of the following places is not generally considered a potential home for life in our solar system?
Jupiter's atmosphere
How do the size and mass of Jupiter's core compare to the size and mass of Earth?
Jupiter's core is about the same size but is 10 times more massive.
What causes the "gaps" observed in the asteroid belt between Mars and Jupiter?
Jupiter's gravity causes orbital resonances that nudge asteroids out of these areas.
Which lists the jovian planets in order of increasing distance from the Sun?
Jupiter, Saturn, Uranus, Neptune
The jovian planets in our solar system are _________.
Jupiter, Saturn, Uranus, and Neptune
Which are thought to have formed farthest from the Sun?
Kuiper belt comets
What evidence suggests that life arises relatively easily?
Life was present on Earth soon after the end of the heavy bombardment period.
How are wavelength, frequency, and energy related for photons of light?
Longer wavelength means lower frequency and lower energy.
All of the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space?
Mars lost any global magnetic field that it may once have had.
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
Mars's interior has cooled so much its molten core layer no longer undergoes convection.
Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Rank the five terrestrial worlds in order of size from smallest to largest.
Moon, Mercury, Mars, Venus, Earth
What do asteroids and comets have in common?
Most are unchanged since their formation in the solar nebula.
According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?
Most of the exceptions are the result of giant impacts or close gravitational encounters.
Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?
Neither the asteroid belt nor Oort cloud would exist.
Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
Not much-on human time scales, the mantle looks like solid rock.
Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true?
Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
Why are terrestrial planets more dense than the jovian planets?
Only dense materials could condense in the inner solar nebula.
Which of the following objects are probably not located in the same general region of the solar system in which they originally formed?
Oort cloud comets
What do we conclude if a planet has few impact craters of any size?
Other geological processes have wiped out craters.
Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?
Our solar nebula must have been blown into space shortly after the formation of the jovian planets.
According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
Which of the following statements is not true about the planets so far discovered around other stars?
Photographs reveal that most of them have atmospheres much like that of Jupiter.
Based on discoveries to date, which of the following conclusions is justified?
Planetary systems are common and planets similar in size to Earth are also common.
Overall, what do current data suggest about planetary types in other planetary systems?
Planets come in a wider range of types than the planets in our solar system.
What is the chief difficulty in attempting to detect planets around other stars?
Planets do not emit visible light, and they are typically at least a billion times fainter than their host stars.
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?
Planets were likely very rare or non-existent around these first-generation stars.
What is the Fermi Paradox?
Reasonable assumptions predict that a galactic civilization should have already arisen in the Milky Way, yet we have absolutely no evidence for it.
In light of what you've learned about the formation of our own solar system, decide whether the discovery should be considered reasonable or surprising.
Reasonable. This is very close to the layout of our solar system
The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Why is Europa considered a good candidate for the possible existence of life?
Strong evidence suggests that it has a deep, subsurface ocean of liquid water.
In light of what you've learned about the formation of our own solar system, decide whether the discovery should be considered reasonable or surprising.
Surprising. According to our current theories, objects that form beyond the jovian planets should include a great deal of ice.
In light of what you've learned about the formation of our own solar system, decide whether the discovery should be considered reasonable or surprising.
Surprising. In the process of nebular capture the formation of large number moons at a jovian planet is more likely that at a terrestrial planet.
Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which of the following explains why?
Temperatures on Jupiter and Saturn are too high for methane to condense.
Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?
Terrestrial planets contain large quantities of ice, and jovian planets do not.
What is the giant impact hypothesis for the origin of the Moon?
The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object.
Which of the following is not evidence supporting the idea that our Moon formed as a result of a giant impact?
The Pacific Ocean appears to be a large crater-probably the one made by the giant impact.
What makes us think that Mars must once have had an atmosphere that was warmer and thicker?
The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
If it turns out that many intelligent civilizations have at one time existed in our galaxy, what is a disturbing conclusion that we could draw from this?
The fact that we have not been contacted by an intelligent civilization, or seen any evidence of one, implies that intelligent civilizations are inherently short-lived.
Which of the following is not considered a potential solution to the question of why we lack any evidence of a galactic civilization?
The galactic civilization probably is undetectable because they operate under different laws of physics from the ones we know.
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?
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?
The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.
Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
The maria formed after the heavy bombardment ended.
Why do Uranus and Neptune appear blue?
The methane gas in their atmospheres absorbs all colors except blue.
Which of the following general statements about Earth's atmosphere is not true?
The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.
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?
The planet must be closer to the star than Earth is to the Sun.
Why does the Doppler method generally give a planet's "minimum mass" rather than an exact mass?
The size of the Doppler shift that we detect depends on the tilt of a planet's orbit.
What do meteorites reveal about the solar system?
They reveal that the age of the solar system is approximately 4.6 billion years.
What is the origin of the large moons orbiting in the equatorial planes of the jovian planets?
They were formed by condensation and accretion in a disk of gas around the planet.
What is a likely reason why a large storm like the Great Red Spot on Jupiter can last so long?
There is no solid surface underneath the storm to sap its energy.
Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?
These planets migrated inward after being born on orbits much farther from their stars.
Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
They actually contain relatively little material in a gaseous state.
Which of the following statements comparing the jovian interiors is not thought to be true?
They all have the same exact set of internal layers, though these layers differ in size.
What do the astrometric, Doppler, and transit methods share in common?
They all search for planets by measuring properties of a star rather than of the planets themselves.
If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?
They are far more technologically advanced than we are.
Which of the following is not a general characteristic of the four jovian planets in our solar system
They are higher in average density than are the terrestrial planets.
Which of the following is a general characteristic of the four jovian planets in our solar system?
They are lower in average density than are the terrestrial planets.
The large Jovian satellites have sizes comparable to Mercury. Why do they have an icy composition compared to Mercury's rocky composition?
They formed beyond the frost line, where ices were more abundant than metals and rock.
Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
They have different numbers of protons in their nucleus
Which of the following is not a characteristic of the outer planets?
They have relatively high densities.
The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from?
They were produced by stars that lived and died before our solar system was born.
Which moon has a thick atmosphere made mostly of nitrogen?
Titan
Why do astronomers believe that Triton is a captured moon?
Triton orbits Neptune in a direction opposite that of Neptune's rotation.
A key clue to how the solar system formed is the observation that all the planets orbit close to the same plane. T or F
True
A planet's size can be determined by observing its transit across a star. T or F
True
Any object moving towards or away from the Earth will show a Doppler shift when observed from Earth. T or F
True
Astronomers have discovered more extrasolar planets around other stars than the number of planets in our own Solar System. T or F
True
Based on our theory of how our own solar system formed, we would expect that other solar systems would be quite common. T or F
True
Ganymede is larger than Mercury, but it is not classified as a planet because it orbits Jupiter as opposed to the sun.
True
Hydrogen exists as a gas, liquid, and solid within Jupiter. T or F
True
Most of Earth's water likely resulted from impacts with icy planetesimals that originated in the outer regions of the solar system. T or F
True
Only one of the moons of the jovian planets has an atmosphere thicker than Earth's atmosphere. T or F
True
Outside the frost line, planetesimals could form into larger objects due to the presence of both rock and ice. T or F
True
The energy levels for electrons vary from one element to another. T or F
True
The more massive planets in the solar system tend to be less dense than the lower mass planets. T or F
True
The requirement of liquid water is the most severe constraint on the development of life. T or F
True
Titan's surface may contain lakes of liquid methane. T or F
True
Without greenhouse gases, water on Earth's surface would be completely frozen. T or F
True
You are currently emitting electromagnetic waves. T or F
True
Which of the following best explain what we think happened to outgassed water vapor on Venus?
Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
Which of the following is not key evidence in support of the idea that all life today shares a common ancestor?
We have identified fossils of the first life forms that ever existed on Earth.
To date, we've found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?
We have not yet been searching for planets at such distances for a long enough time.
What do we mean when we say that the terrestrial worlds underwent differentiation?
When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.
Which of the following statements about X-rays and radio waves is not true?
X-rays travel through space faster than radio waves.
Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?
Yes. All three methods give us direct information about a planet's orbital period, from which we can use Newton's version of Kepler's third law to calculate the planet's distance.
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?
You'll have 0.25 kilogram of the radioactive substance remaining.
An icy leftover planetesimal orbiting the Sun is
a comet.
Which of the following is the most basic definition of a greenhouse gas?
a gas that absorbs infrared light
The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________.
a large baked potato takes longer to cool than a small baked potato
What is the Cassini division in Saturn's rings?
a large gap, visible from Earth, produced by an orbital resonance with the moon Mimas
A terrestrial world's lithosphere is ________.
a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle
What is the Great Red Spot?
a long-lived, high-pressure storm on Jupiter
Which of the following best describes what we mean by a habitable world?
a planet or moon that could support life
According to the laws of thermal radiation, hotter objects emit photons with _________.
a shorter average wavelength
Which of the following observations of an extrasolar planet system would be inconsistent with the nebular theory of planet formation?
a system in which all the planets orbit in completely different planes
According to fossil evidence, how far back in time did life on Earth exist?
about 3.5 billion years or more
Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is ________.
about the thickness of a sheet of paper
What process initially caused the terrestrial planets to be hot enough to be entirely molten?
accretion
A rocky leftover planetesimal orbiting the Sun is
an asteroid.
Which of the following is NOT considered crucial for life to exist on some world?
an atmosphere
Saturn's rings
are continually supplied by impacts with small moons.
Why do scientists say that evolution is a "theory"?
because it explains a great deal about life and is supported by an enormous body of evidence
Why is the sky blue (on Earth)?
because molecules scatter blue light more effectively than red light
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?
because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system
The greatest number of asteroids are found
between 2 and 3 AU from the sun.
The asteroid belt is located _________.
between the orbits of Mars and Jupiter
What is the most likely method in which Jupiter generates its internal heat?
by contracting, changing gravitational potential energy into thermal energy
Which of the following did not occur during the collapse of the solar nebula?
concentrating denser materials nearer the Sun
Which of the following best describes the internal layering of Jupiter, from the center outward?
core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer
From center to surface, which of the following correctly lists the interior layers of a terrestrial world?
core, mantle, lithosphere, crust
Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?
countless icy particles, ranging in size from dust grains to large boulders
Which of the following methods has led to the most discoveries of extrasolar planet candidates?
detecting the dip in measured brightness as the planet crosses our line of sight to the star
About how often does a 1-kilometer object strike the Earth?
every million years
Planetary orbits in our solar system are:
fairly circular and in the same plane.
The Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?
features of erosion, including what appeared to be dry river valleys and lakebeds
Volcanism is more likely on a planet that
has high internal temperatures.
Which internal heat source still actively generates heat within the terrestrial worlds today?
heat from radioactive decay
A planet is most likely to have tectonic activity if it has
high internal temperature.
The composition of the solar nebula was 98%
hydrogen and helium
What is Jupiter's main ingredient?
hydrogen and helium
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?
hydrogen and helium gas; hydrogen compounds; rock; metal
Which of the following types of material can condense into what we call ice at low temperatures?
hydrogen compounds
The processes responsible for all surface geology on the terrestrial planets are ________
impact cratering, volcanisms, tectonics, and erosion
Which of the following is considered by biologists to be a likely place where life might have first arisen on Earth?
in hot water near undersea volcanoes
According to the nebular theory, where should jovian planets form?
in the cold outer regions of the disk, where rocks, metals, and ices can condense
Where did comets that are now in the Kuiper belt originally form?
in the same region where they are found today
The astrometric method of planet detection works best for
massive planets around nearby stars.
The terrestrial planet cores contain mostly metal because
metals sank to the center during a time when the interiors were molten throughout.
What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
methane
In essence, the Kepler mission searched for extrasolar planets by ____________.
monitoring stars for slight dimming that might occur as unseen planets pass in front of them
If we could put all the asteroids together, their total mass would be ________.
much less than the mass of any terrestrial planet
Where did comets that are now in the Oort cloud originally form?
near the jovian planets
What is the most abundant gas in Titan's atmosphere?
nitrogen
If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ________.
of global climate effects initiated by dust and smoke that entered the atmosphere after the impact
According to current scientific understanding, the idea that the Milky Way Galaxy might be home to a civilization millions of years more advanced than ours is
one reasonable answer to Fermi's paradox.
Some jovian planets give off more energy than they receive because of
ongoing contraction or differentiation.
The transit method allows us in principle to find planets around __________.
only a small fraction of stars that have planets
Saturn's many moons affect its rings through
orbital resonances.
In essence, the nebular theory holds that _________.
our solar system formed from the collapse of an interstellar cloud of gas and dust
Which of the following gases best absorbs ultraviolet light?
ozone
Which of the following gases, which we can detect (if present) in infrared spectra, would be a strong indicator of life on another planet?
ozone
Which of the following was the most important for maintaining the Earth's stable climate over the time it took for large organisms to evolve?
plate tectonics
Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
plate tectonics and liquid water oceans
The astrometric method looks for planets with careful measurements of a star's _________.
position in the sky
In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), we expect the term fciv to be small if ________.
primitive life is common but intelligent life is rare
Thermal radiation is defined as _________.
radiation with a spectrum whose shape depends only on the temperature of the emitting object
From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
radio, infrared, visible light, ultraviolet, X-rays, gamma rays
Which of the following best describes the lunar maria?
relatively smooth, flat plains on the Moon
Which of the following observational techniques is appropriate for measuring Doppler shifts?
spectroscopy (taking a spectrum)
Measured densities of extrasolar planets range from ________.
styrofoam to iron
Sunsets and sunrises often appear red because
sunlight must pass through more atmosphere, which scatters the shorter wavelengths more than the longer wavelengths, allowing more red light to reach your eye.
The first confirmed detections of extrasolar planets occurred in ____________
the 1990s
Overall, Jupiter's composition is most like that of ________.
the Sun
Which of the following is not an example of tectonics?
the gradual disappearance of a crater rim as a result of wind and rain
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
the law of conservation of angular momentum
The age of the solar system can be established by radiometric dating of
the oldest meteorites.
The depth of the dip in a star's brightness due to the transit of a planet depends most directly on
the planet's size.
What observational evidence supports the idea that Mercury shrank after it formed?
the presence of many long, tall cliffs
In the context of planetary geology, what do we mean by outgassing?
the release by volcanism of gases that had been trapped in a planetary interior
One star is emitting primarily visible light and another star is emitting primarily infrared light. Which star is hotter?
the star emitting visible light
Which of the following best describes erosion?
the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
The reason that most extrasolar planets discovered by the transit method are found close to their parent stars is
they transit more frequently and are more likely to be detected in the short time we have been searching for them.
What mechanism is most responsible for generating the internal heat of Io that drives its volcanic activity?
tidal heating
Observations of young stars (as well as theory) tell us that when the Sun was young, the solar wind
was stronger than it is today
Which of the following best describes the composition of the particles forming Saturn's rings?
water ice
