Astronomy 101 Chapters 8-14
Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?
Astronomers have detected small lakes of liquid water on Europa's surface.
Suppose you are using the Doppler technique 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 a transit.
How is the sunspot cycle directly relevant to us here on Earth?
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits?
Some moons have orbits that are "backwards" (compared to their planet's rotation) or highly inclined to their planet's equator.
Which of the following best explains why we can rule out the idea that planets are usually formed by near-collisions between stars?
Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars.
What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
The atmosphere is too cold and thin for liquid water today, yet we see evidence of flowing water in the past.
Earth has been gradually warming in recent decades, and very strong evidence indicates that the cause of this warming is
human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere
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
Which of the following is the underlying reason why Venus has so little wind erosion?
its slow rotation
What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?
its small size compared to Earth
Which of the following is most unlikely to be found on Titan?
lakes of liquid water in the warmer equatorial regions
Which two factors are most important to the existence of plate tectonics on Earth?
mantle convection and a thin lithosphere
The cores of the terrestrial worlds are made mostly of metal because ______.
metals sunk to the centers a long time ago when the interiors were molten throughout
If we could put all the asteroids in the asteroid belt together, their total mass would be ______.
much less than the mass of Mercury.
Gaps in the asteroid belt (often called Kirkwood gaps) are caused by ______.
orbital resonances with Jupiter
Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
plate tectonics and liquid water oceans
What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?
plate tectonics and widespread erosion
The astrometric method looks for planets with careful measurements of a star's _________.
position in the sky
Which characteristic of Earth explains why Earth has the ozone necessary for an ultraviolet-absorbing stratosphere?
the existence of photosynthetic life
When you see the bright flash of a meteor, what are you actually seeing?
the glow of heated air surrounding a small particle as it burns up in our atmosphere.
The age of the solar system can be established by radiometric dating of
the oldest meteorites.
In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?
the rings of Saturn
In the context of the formation of planets in the solar nebula, the frost line marks the distance from the Sun beyond which
the temperature was low enough for hydrogen compounds to condense into ices.
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
What is Pluto's moon Charon thought to have in common with our own Moon?
It probably formed as a result of a giant impact.
You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?
It was created by the impact of an object about 1 kilometer across.
When is/was gravitational contraction an important energy generation mechanism for the Sun?
It was important when the Sun was forming from a shrinking interstellar cloud of gas.
What would happen to Jupiter if we could somehow double its mass?
Its density would increase but its diameter would barely change.
Which of the following most likely explains why Venus does not have a global magnetic field like Earth?
Its rotation is too slow.
Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?
It has been on its current orbit for only a very short time compared to the age of our solar system.
Which of the following statements best describes the size of the largest asteroid, Ceres?
It is a little less than half the diameter of our Moon.
Which of the following statements about Earth's troposphere is not generally true?
It is the layer of the atmosphere in which ozone absorbs dangerous ultraviolet light from the Sun.
What is Eris?
An icy object that orbits in the Kuiper belt and is more massive than Pluto
Which of the following is the best answer to the question, "Why does the Sun shine?"
As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
In very general terms, how do the temperature structures of the atmospheres of Venus and Mars differ from that of Earth?
They lack ultraviolet-absorbing stratospheres.
What key evidence suggests that Triton is a captured moon?
Triton orbits Neptune in a direction opposite that of Neptune's rotation.
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 jovian planet has the most extreme seasonal changes, and why?
Uranus, because of its extreme axis tilt.
All the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450 C hotter than the surface of Earth?
Venus has a much stronger greenhouse effect than Earth.
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?
3.75 billion years
All of the following have occurred over long periods of time on Earth. Which one is not thought to have played a major role in long-term changes in Earth's climate?
A gradual rise in the atmospheric content of oxygen.
In the context of plate tectonics, what is a subduction zone?
A place where seafloor plate is sliding under a continental plate.
Why is the Coriolis effect so weak on Venus?
Because Venus rotates so slowly.
According to the nebular 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, whereas ice also condensed in the outer solar system.
Why is thermal escape of atmospheric gas much easier from the Moon than from Earth?
Because the Moon's gravity is so much weaker than Earth's.
How can we determine the reflectivity of an asteroid?
By comparing its brightness in visible light to its brightness in infrared light.
How can we measure the strength of magnetic fields on the Sun?
By looking for the splitting of spectral lines in the Sun's spectrum.
If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?
Fusion reactions in the Sun have ceased within the past few minutes.
Which of the following best explains why the Sun's luminosity gradually rises over billions of years?
Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.
Why does the Sun emit neutrinos?
Fusion in the Sun's core creates neutrinos.
Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
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.
When we see a meteor shower, it means that _________.
Earth is crossing the orbit of a comet
What would happen to Earth if we somehow moved our planet to the orbit of Venus?
Earth would suffer a runaway greenhouse effect and become as hot or hotter than Venus.
Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.
Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
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.
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.
According to our modern science, which of the following best explains why the vast majority of the mass of our solar system consists of hydrogen and helium gas?
Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young.
Where do scientists think that Jupiter's strong magnetic field is generated?
In its metallic hydrogen layer.
All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io?
Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites.
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?
It flattened as a natural consequence of collisions between particles in the nebula.
Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?
Jovian moons contain much more ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
Which of the following best describes why the Sun emits most of its energy in the form of visible light?
Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
All 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 is thought to explain why Venus has so much more atmospheric gas than Earth?
Most of the gases that have been released from volcanoes on Earth later returned to the surface.
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.
A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield to protect you and your family. (It's even "on sale" !) Why do you turn down this excellent offer?
Neutrinos rarely, if ever, interact with other matter.
Does Venus have auroras around its poles, like the Earth? Why or why not?
No, because it lacks a global magnetic field.
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
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 denser than jovian planets?
Only dense materials could condense in the inner solar nebula.
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 current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?
Oxygen released by life was removed from the atmosphere by chemical reactions with surface rocks until the surface rock could absorb no more.
According to current models 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.
All of the following statements are true. Which one makes it possible to learn of the existence of extrasolar planets without seeing the planets themselves?
Planets exert gravitational tugs on their stars that cause stars to orbit around the center of mass of their planetary systems.
Which of the following is not a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt?
Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.
Why won't Pluto collide with Neptune?
Pluto orbits the Sun exactly 2 times for every 3 Neptune orbits, which ensures they never come close together.
Which planet may have helium rain in its interior, and what does this rain do?
Saturn, where it generates heat as it falls downward.
Why are there fewer large impact craters on the Earth's seafloor than on the continents?
Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.
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.
Which of the following is a real piece of evidence (from the New Horizons mission) pointing to recent or ongoing geological activity on Pluto?
Surface regions that suggest glacial movement of frozen ices of nitrogen and methane.
Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?
Temperatures on Jupiter and Saturn are too high for methane to condense.
Which of the following is not a line of evidence supporting the hypothesis 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.
Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
How does the Sun's mass compare to Earth's mass?
The Sun's mass is about 300,000 times the mass of the Earth.
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support the nebular theory's scenario about for the formation of the terrestrial planets?
The appearance and composition of these meteorites is just what we'd expect if metal and rock condensed and accreted as the nebular theory suggests.
How can we best observe the Sun's chromosphere and corona?
The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
The core would heat up, fusion rates would increase, the core would re-expand.
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle.
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
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?
The law of conservation of energy
Which of the following is a major reason why it is do difficult to obtain direct images of extrasolar planets?
The light is of the planets overwhelmed by the light from their star.
Which of the following best why we see horizontal "stripes" in photographs of Jupiter and Saturn?
The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.
Which of the following is not generally true of all the terrestrial world lithospheres?
The lithosphere is broken into a set of large plates that float upon the softer rock below.
Why were scientists surprised when they first discovered the existence of planets with Jupiter-like masses orbiting close to their stars (the "hot Jupiters")?
The nebular theory predicts that Jovian planets should only form at much larger distances from their stars.
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 is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?
The region is full of gases that become ionized after they are released from volcanoes on Io.
Which statement about Saturn's rings is not true?
The rings must look much the same today as they did shortly after Saturn formed.
Suppose that Earth's ice caps melted, but everything else about the Earth's surface and atmosphere stayed the same. What would happen to Earth's average surface temperature?
The surface temperature would increase.
What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
The temperatures at which various materials will condense from gaseous form to solid form.
According to the nebular theory of solar system formation, what key difference in their early formation explains why the Jovian planets ended up so different from the terrestrial planets?
The terrestrial planets formed inside the frost line of the solar nebula and the Jovian planets formed beyond it.
Why does Jupiter have three distinct layers of clouds?
The three layers represent clouds made of gases that condense at different temperatures.
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
What do we mean when we say that the Sun is in gravitational equilibrium?
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems 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 star systems?
There were no comets or asteroids in these first-generation star systems.
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.
Why do sunspots appear dark in pictures of the Sun?
They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
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 best describes convection?
Warm material expands and rises while cool material contracts and falls.
Which of the following is not caused by the Coriolis effect on Earth?
Water going down a drain swirls in opposite directions in the northern and southern hemispheres.
The Sun's surface seethes and churns with a bubbling pattern. Why?
We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
Which of the following choices is not a way by which we can study the inside of the Sun?
We can send a space probe into the Sun's photosphere.
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.
Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?
Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.
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
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
The intricate patterns visible in an X-ray image of the Sun generally show _________.
extremely hot plasma flowing along magnetic field lines