Which of the following statements about our Sun is NOT true? The Sun’s diameter is about five times that of Earth. |
The Sun’s diameter is about five times that of Earth. |
The planet in our solar system with the highest average surface temperature is __________. Earth |
Venus |
Which jovian planet does NOT have rings? Jupiter |
All the jovian planets have rings. |
What is the Kuiper belt? a region of the solar system that extends almost a fourth of the way to the nearest stars and contains a trillion comets with orbits going in all directions around the Sun |
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets |
Which of the following statements about Pluto is true? It is the largest known object that is considered to be a dwarf planet. |
It has more in common with comets in the Kuiper belt than it does with terrestrial planets like Earth. |
Suppose you view the solar system from high above Earth’s North Pole. Which of the following statements about planetary orbits will be true? The inner planets orbit the Sun counterclockwise while the outer planets orbit the Sun clockwise. |
All the planets orbit counterclockwise around the Sun. |
When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals EXCEPT ______. ammonia |
carbon dioxide |
What is the Kuiper belt? the most prominent ring of Saturn that is visible in photographs |
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets |
What is the Oort cloud? It is a giant storm in the atmosphere of Saturn. |
It’s not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances. |
In essence, the nebular theory holds that _________. The nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our Sun and another star. |
our solar system formed from the collapse of an interstellar cloud of gas and dust |
What do we mean by the frost line when we discuss the formation of planets in the solar nebula? It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds. |
It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense. |
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. |
It got hotter, its rate of rotation increased, and it flattened into a disk. |
What is the giant impact hypothesis for the origin of the Moon? The Moon formed just like Earth, from accretion in the solar nebula. |
The Moon formed from material blasted out of Earth’s mantle and crust by the impact of a Mars-size object. |
According to modern scientific dating techniques, approximately how old is the solar system? 10,000 years |
4.5 billion years |
Which of the following types of material can condense into what we call ice at low temperatures? hydrogen compounds |
hydrogen compounds |
According to our theory of solar system formation, what are asteroids and comets? leftover planetesimals that never accreted into planets |
leftover planetesimals that never accreted into planets |
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 0.75 kilogram of the radioactive substance remaining. |
You’ll have 0.25 kilogram of the radioactive substance remaining. |
Our Moon is about the same size as moons of the other terrestrial planets. True |
False |
On average, Venus is the hottest planet in the solar system – even hotter than Mercury. True |
True |
What’s unusual about our Moon? It’s the only moon that orbits a terrestrial planet. |
It’s surprisingly large relative to the planet it orbits. |
Based on your study of the Interactive Figure, which of the following is not one of the four major features of the solar system? Planets fall into two major categories (terrestrial and jovian). |
The solar system contains eight planets plus dwarf planets (including Ceres, Pluto, and Eris). |
Study the features relating to the first characteristic (orderly motions); click on the inner or outer solar system to see the planets in motion, then scroll over the planets to see diagrams of their axis tilts. Which of the following correctly describe patterns of motion in the solar system? Inner planets orbit the Sun in the opposite direction from the outer planets. |
Planets closer to the Sun move around their orbits at higher speed than planets farther from the Sun. All the planets (not counting Pluto) orbit the Sun in nearly the same plane. All the planets (not counting Pluto) have nearly circular orbits. |
Now consider the second major characteristic (two types of planets). Which of the following statements are true? Jovian planets are higher in average density than terrestrial planets. |
Jovian planets are larger in mass than terrestrial planets. Jovian planets orbit farther from the Sun than terrestrial planets. Jovian planets are larger in size than terrestrial planets. Jovian planets have more moons than terrestrial planets. |
The solar system contains vast numbers of small bodies, which we call asteroids when they are rocky and comets when they are icy. These small bodies are concentrated in the region(s) of the solar system that we call __________. the Doppler belt |
the Oort cloud the Kuiper belt the asteroid belt |
All the following statements are true. Which of them are considered to be "exceptions" to the general trends described by the first three major characteristics of the solar system? Jupiter’s largest moon, Ganymede, is even larger than Earth’s moon. |
Venus rotates in a direction opposite to the rotation of the other terrestrial planets. Uranus rotates with an axis tilt that lies nearly in the ecliptic plane. Our Moon has a diameter more than 1/4 the diameter of Earth. |
Consider only the observed patterns of motion in the solar system. Scientifically, which of the following possible conclusions is justified from the patterns of motion alone? The planets were not born within the past million years, but instead they must have been born billions of years ago. |
The planets were not each born in a separate, random event. |
Now consider why the observed patterns of motion lead to the conclusion that the planets were not born in separate, random events. The reason for this conclusion is that, if the planets had been born in separate, random events, we would expect that __________. there would be many different types of planets, rather than just two major types |
planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane |
Today, scientists have a theory (the nebular theory) that explains all the major characteristics of the solar system. In science, we expect a theory like this not only to explain the observed characteristics of our solar system but also to __________. make testable predictions about other solar systems |
make testable predictions about other solar systems |
Listed following are characteristics that can identify a planet as either terrestrial or jovian. Match these to the appropriate category. |
Terrestrial planets: -small size -solid, rocky surface -located within the inner solar system Jovian planets: -primarily composed of hydrogen, helium, and hydrogen compounds -numerous orbiting moons -extensive ring systems -low average density |
The following images show six objects in our solar system. Rank the objects from left to right based on their average distance from the Sun, from farthest to closest. (Not to scale.) |
Farthest to closest: Pluto, Saturn, Jupiter, Mars, Earth, Mercury |
The following images show six objects in our solar system. Rank these objects from left to right based on their mass, from highest to lowest. (Not to scale.) |
Highest to lowest mass: Sun, Jupiter, Earth, Mars, Mercury, Pluto |
The images below show six objects in our solar system. Rank these objects by size (average equatorial radius), from largest to smallest. (Not to scale.) |
Largest to smallest radius: Sun, Jupiter, Earth, Mars, Mercury, Pluto |
The following images show five planets in our solar system. Rank these planets from left to right based on their average surface (or cloud-top) temperature, from highest to lowest. (Not to scale.) |
Highest to lowest temperature: Mercury, Earth, Mars, Jupiter, Neptune |
The following images show five planets in our solar system. Rank these planets from left to right based on the amount of time it takes them to orbit the Sun, from longest to shortest. (Not to scale.) |
Longest to shortest time: Neptune, Jupiter, Mars, Earth, Mercury |
The following images show four planets in our solar system. Rank these planets from left to right based on the number of moons that orbit them, from highest to lowest. (Not to scale.) |
Highest to lowest number: Jupiter, Mars, Earth, Mercury |
The mass of the Sun compared to the mass of all the planets combined is like the mass of an elephant compared to the mass of a cat. True |
True |
The weather conditions on Mars today are much different than they were in the distant past. True |
True |
Moons cannot have atmospheres, active volcanoes, or liquid water. True |
False |
Saturn is the only planet in the solar system with rings. True |
False |
Which terrestrial planets have had volcanic activity at some point in their histories? only Earth |
all of them |
Large moons orbit their planets in the same direction the planet rotates: most of the time. |
most of the time. |
Pluto orbits the Sun in the opposite direction of all the other planets. True |
False |
How many of the planets orbit the Sun in the same direction that Earth does? a few |
All |
What fraction of the moons of the planets orbit in the same direction that their planets rotate? some |
Most |
When the solar nebula was about 40000 AU in radius, how fast would the same material have orbited? (Remember that when the cloud was larger, motions were more random, so we can calculate only the average.) Use the law of conservation of angular momentum (see Section Conservation Laws in Astronomy). v≈5km/s |
v≈5m/s |
Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, as shown in the animation, the nebular theory predicts that a cloud will rotate rapidly once it shrinks to a small size. What physical law explains why a cloud will rotate rapidly as it collapses? the law of conservation of angular momentum |
the law of conservation of angular momentum |
The nebular theory also predicts that the cloud should heat up as it collapses. What physical law explains why it heats up? the law of conservation of energy |
the law of conservation of energy |
The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk? Gravity pulls more strongly on material along the rotation axis than perpendicular to it, bringing this material downward into a disk. |
Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole. |
As you’ve seen, the nebular theory predicts that a cloud that gives birth to planets should have the shape of a spinning disk. Which observable property of our solar system supports this prediction? The orbit of Earth’s Moon lies very close to the ecliptic plane. |
All the planets orbit the Sun in the same direction and in nearly the same plane. |
The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system? After the planets formed, the Sun’s gravity pulled the dense terrestrial planets inward, leaving only jovian planets in the outer solar system. |
Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets. |
Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems? Planetary systems should generally have all planets orbiting in nearly the same plane. |
Planetary systems should generally have all planets orbiting in nearly the same plane. Other planetary systems should have the same two types of planets: terrestrial and jovian. Planetary systems should be common. Jovian planets always form farther from their star than terrestrial planets. |
Listed following are statements that, based on our current theory of solar system formation, apply either to the formation of terrestrial planets or of jovian planets, but not both. Match these to the appropriate category. |
Terrestrial planets: -surfaces dramatically altered during the heavy bombardment -accreted from planetesimals of rock and metal Jovian planets: -accreted from icy planetesimals -formed in a region of the solar system with lower orbital speeds -ejected icy planetesimals that are now Oort cloud comets -formed in regions cold enough -large moons formed in surrounding disks of material |
What is Jupiter’s main ingredient? rock and metal |
hydrogen and helium |
Which lists the major steps of solar system formation in the correct order? collapse, accretion, condensation |
collapse, condensation, accretion |
Leftover ice-rich planetesimals are called comets. |
comets. |
Why didn’t a terrestrial planet form at the location of the asteroid belt? There was never enough material in that part of the solar nebula. |
Jupiter’s gravity kept planetesimals from accreting. |
The materials that made up the solar nebula can be categorized into the four general types as follows. Rank these materials from left to right based on their abundance in the solar nebula, from highest to lowest. |
Highest to lowest abundance: hydrogen and helium gas, hydrogen compounds, rock, metals |
The materials that made up the solar nebula can be categorized into these four general types. Rank these materials from left to right based on the temperature at which each would condense into a solid, from highest to lowest. Note: For a substance that does not condense at all, rank it as very low temperature. |
Highest to lowest temperature: metals, rock, hydrogen compounds, hydrogen and helium gas |
As you’ve learned from Part B, hydrogen and helium gas never condense under conditions found in the solar nebula. The remaining three categories of material in the solar nebula are shown again here. Rank these materials from left to right based on the distance from the Sun at which they could condense into a solid in the solar nebula, from farthest to closest. |
Farthest to closest: hydrogen compounds, rock, metals |
What substances were found within the inner 0.3 AU of the solar system before planets began to form? nothing at all |
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form |
What substances existed as solid flakes within the inner 0.3 AU of the solar system before planets began to form? none |
none |
Where would you expect terrestrial planets to form in the solar nebula? within the inner 0.3 AU |
anywhere between 0.3 AU and the frost line |
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________. only rocks and metals |
rocks, metals, and ices |
Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last. |
First to last stage: large cloud of gas and dust, contraction of solar nebula, condensation of solid particles, accretion of planetesimals, clearing the solar nebula |
Sort the following hypothetical discoveries into the appropriate bins as follows: |
Consistent with theory: -Beyond its jovian planets, a star has two ice-rich objects as large as Mars. -A star is surrounded by a disk of gas but has no planets. -Of a star’s 5 terrestrial planets, 1 has a moon as large as Earth’s moon. -A star has 20 planets. Not consistent with theory: -All 6 of a star’s terrestrial planets have a moon as large as Earth’s moon. -A star’s 4 jovian planets formed in its inner solar system and its 4 terrestrial planets formed farther out. – A star’s 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets. -A star has 9 planets, but none orbit in close to the same plane. |
Two hypothetical discoveries in Part A deal with moons that, like Earth’s moon, are relatively large compared to their planets. Which of the following best explains why finding 1 planet with such a moon is consistent with the nebular theory, while finding 6 planets with such moons is not consistent? Unusually large moons form in giant impacts, which are relatively rare events. |
Unusually large moons form in giant impacts, which are relatively rare events. |
Consider the hypothetical discovery from Part A reading: "A star’s 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets." This discovery would be inconsistent with the nebular theory because the theory holds that __________. terrestrial planets should orbit in a different plane from the plane of the jovian planets |
all the planets formed in a rotating, disk-shaped nebula |
Consider the hypothetical discovery from Part A reading: "Beyond its jovian planets, a star has two ice-rich objects as large as Mars." This discovery is consistent with the nebular theory, because this theory predicts that _________. ice-rich objects the size of terrestrial planets should exist in all solar systems |
this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula |
What’s the leading theory for the origin of the Moon? It formed along with Earth. |
It formed from the material ejected from Earth in a giant impact. |
About how old is the solar system? 4.5 million years |
4.5 billion years |
In a rock from the lunar maria, you find that 68% of the original uranium-238 remains, while the other 32% has decayed into lead. Is this rock older or younger than the highlands rock? older |
younger |
Assuming that other planetary systems form in the same way as our solar system formed, where would you expect to find terrestrial planets? Terrestrial planets will likely be located farther from the planetary system’s star than any jovian planets. |
Terrestrial planets will likely be located nearer the planetary system’s star than any jovian planets. |
Compared to terrestrial planets, jovian planets are __________. more massive and higher in average density |
more massive and lower in average density |
Which planet is approximately halfway between Pluto’s orbit and the Sun? Mars, the fourth planet from the Sun |
Uranus, the seventh planet from the Sun |
The dwarf planet Eris was discovered in 2005, orbiting the Sun at an average distance about twice that of Pluto. In which of the following ways do Pluto and Eris differ from the terrestrial and jovian planets in our solar system? Both Pluto and Eris are smaller than any of the terrestrial planets. |
Both Pluto and Eris are smaller than any of the terrestrial planets. Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or jovian planets. Both Pluto and Eris are less massive than any of the terrestrial or jovian planets. |
1. _______ is about 30 times as far from the Sun as our own planet. |
Neptune |
2. _______ is the planet with the highest average surface temperature. |
Venus |
3. The planet with the lowest average density is______. |
Saturn |
4. The planet that orbits closest to the Sun is _________. |
Mercury |
5. The only rocky planet to have more than one moon is _______. |
Mars |
6. _________ is the jovian planet that orbits closest to the Sun. |
Jupiter |
7. _________ has a rotational axis that is tilted so much it lies nearly in the plane of its orbit. |
Uranus |
8. Most of the surface of _______ is covered with liquid water. |
Earth |
Which of the following is not a major pattern of motion in the solar system? Nearly all comets orbit the Sun in same direction and roughly the same plane. |
Nearly all comets orbit the Sun in same direction and roughly the same plane. |
Which of the following is not a major difference between the terrestrial and jovian planets in our solar system? Terrestrial planets orbit much closer to the Sun than jovian planets. |
Terrestrial planets contain large quantities of ice and jovian planets do not. |
Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt while icy comets are found primarily in the Oort cloud." What’s wrong with this statement? The Kuiper belt contains icy comets, not rocky asteroids. |
The Kuiper belt contains icy comets, not rocky asteroids. |
Which of the following is not a real difference between asteroids and comets? Most asteroids are located much nearer to the Sun than most comets. |
Asteroids orbit the Sun while comets just float randomly around in the Oort cloud. |
The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system? The diameter of Earth’s Moon is about 1/4 that of Earth. |
The diameter of Earth’s Moon is about 1/4 that of Earth. |
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is ______. much larger |
much larger |
How is Einstein’s famous equation, E=mc 2, important in understanding the Sun? It explains why the Sun is so massive. |
It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each second. |
Venus has a higher average surface temperature than Mercury. Why? Because it is closer to the Sun. |
Because its surface is heated by an extreme greenhouse effect. |
In what way is Venus most similar to Earth? Both planets have very similar atmospheres. |
Both planets are nearly the same size. |
Which of the following statements about the object called Eris is not true? It orbits the Sun in the same general direction as the planets. |
It is thought to be the first example of a new class of object. |
Mars has two moons that are most similar in character to: small asteroids |
small asteroids |
Imagine that an alien spaceship crashed onto Earth. Which statement would most likely be true? The crash would create a noticeable crater. |
It would crash in the ocean |
Which planet listed below has the most extreme seasons? Uranus |
Uranus |
In what way is Pluto more like a comet than a planet? It sometimes enters the inner solar system. |
It is made mostly of rock and ice. |
Why was it advantageous for the Voyager mission to consist of flybys rather than orbiters? Each individual spacecraft was able to visit more than one planet. |
Each individual spacecraft was able to visit more than one planet. |
Why has NASA sent recent orbiters to Mars (such as Mars Reconnaissance Orbiter) on trajectories that required them to skim through Mars’s atmosphere before settling into their final orbits? It allowed the spacecraft to collect samples of the atmospheric gas for return to Earth. |
It saves money because the spacecraft uses atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines. |
This photograph was taken on the surface of another world in our solar system. What world is it?
Venus |
Mars |
Which pair of photos below shows Earth correctly scaled in comparison to the Sun? |
When Earth is the smallest |
What planet is this, and how do you know? Saturn, because it is the only planet with rings. |
Saturn, because of its colors and bright, wide rings. |
Which pair of photos below shows Earth correctly scaled in comparison to Jupiter? |
When Earth is the smallest |
In this photograph, the large and bright object in the sky is: a comet |
a comet |
This famous photograph taken by the Voyager spacecraft shows _________. A close-up of the rings of Neptune. |
Earth as viewed from the outskirts of the solar system. |
In this perspective view of the solar system, the sizes of the planets are ___________ relative to the sizes of their orbits. correctly scaled |
exaggerated about a million times |
This photo shows ___________. a dwarf planet |
an asteroid |
What do we see in this photo? Pluto |
Neptune |
What planet is shown in this photo? Mercury |
Mars |
1. The first few hundred million years of the solar system 19s history were the time of the __________, during which Earth suffered many large impacts. |
heavy bombardment |
2. The era of planet formation ended when the remaining hydrogen and helium gas of the solar nebula was swept into interstellar space by the __________. |
solar wind |
3. Ice can form from a gas through the process of ___________. |
condensation |
4. Hydrogen compounds in the solar system can condense into ices only beyond the __________. |
frost line |
5. Our Moon was most likely formed by a collision between Earth and a Mars-sized ____________. |
planetesimal |
6. Mars was formed by the ________ of smaller objects. |
accretion |
7. Our solar system was created by the gravitational collapse of the _________. |
solar nebula |
8. ______________ allows us to determine the age of a solid rock. |
radiometric dating |
What does this photo show?
a galaxy much like our Milky Way Galaxy |
an interstellar cloud that will ultimately give birth to thousands of star systems |
This photo shows a "debris disk" around a nearby star. What is the significance of this type of "debris disk"? It shows that stars really can be surrounded by flattened disks of dust and gas. |
It shows that stars really can be surrounded by flattened disks of dust and gas. |
This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why cloud spins faster as it shrinks in size? the law of conservation of angular momentum |
the law of conservation of angular momentum |
This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why the center of the cloud becomes so much hotter as the cloud shrinks in size? the universal law of gravitation |
the law of conservation of energy |
This diagram represents the solar nebula early in its history, and shows the location of the <i>frost line</i>. Suppose you discover an object that is made of metal, rock, and ice. In which region of the solar system did it form? 1 |
4 |
This photo shows a slice of a meteorite. What is its significance? It shows that accretion really did make objects many kilometers in size during the early stages of the formation of our solar system. |
The shiny metal flakes embedded in rock are just what we expect if condensation really occurred as the nebular theory predicts. |
What is being shown in the zoom-out box of this painting? the formation of Saturn’s rings |
the formation of a jovian planet |
This painting shows an object colliding with Earth. What is thought to have happened as a result of this collision? It led to the extinction of the dinosaurs. |
It blasted away debris that then accreted in Earth orbit to form the Moon. |
What can you conclude from studying this graph? It takes 5 billion years to turn potassium-40 into argon-40. |
Potassium-40 has a half-life of 1.25 billion years. |
You find a rock containing radioactive potassium-40 and its decay product argon-40. You assume that all the argon-40 was made from radioactive decay of potassium-40. The rock now has twice as much argon-40 as potassium-40; that is, 2/3 of the original potassium-40 has decayed into argon-40 while 1/3 remains in the rock. Based on this graph, about how old is the rock? 3 billion years |
2 billion years |
Which of the following best explains why we can rule out the idea that planets are usually formed by near-collisions between stars? A near collision might have created planets, but it could not have created moons, asteroids, or comets. |
Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars. |
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? All the other elements escaped from the solar nebula before the Sun and planets formed. |
Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young. |
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 angular momentum |
The law of conservation of energy |
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size? Einstein’s law E=mc2 |
The law of conservation of angular momentum |
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 was fairly flat to begin with, and retained this flat shape as it collapsed. |
It flattened as a natural consequence of collisions between particles in the nebula. |
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 atomic mass numbers of various materials. |
The temperatures at which various materials will condense from gaseous form to solid form. |
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? Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets. |
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal. |
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? The meteorites sizes are just what we’d expect if metal and rock condensed and accreted as our theory suggests. |
The meteorites appearance and composition is just what we’d expect if metal and rock condensed and accreted as our theory suggests. |
According to present understanding, which of the following statements about the solar wind is not true? It consists of charged particles blown off the surface of the Sun. |
It is even stronger today than it was when the Sun was young. |
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. |
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars. |
What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits? Astronomers have observed moons being captured. |
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 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. |
The Pacific Ocean appears to be a large crater – probably the one made by the giant impact. |
Why are terrestrial planets denser than jovian planets? Gravity compresses terrestrial planets to a higher degree, making them denser. |
Only dense materials could condense in the inner solar nebula. |
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 |
3.75 billion years |
How do scientists determine the age of the solar system? Radiometric dating of meteorites |
Radiometric dating of meteorites |
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? All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter. |
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. |
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? Like the jovian planets in our solar system, the jovian planets in these first-generation systems were orbited by rings. |
There were no comets or asteroids in these first-generation star systems. |
What is an extrasolar planet? a planet that orbits a star that is not our own Sun |
a planet that orbits a star that is not our own Sun |
The first confirmed detections of extrasolar planets occurred in ____________. 2011 |
the 1990s |
Based on available data, what kind of objects in our solar system do most of the known extrasolar planets resemble? Kuiper belt objects |
jovian planets |
Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets? 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. |
Jovian planets can migrate from the orbits in which they are born. |
Which detection techniques can find the planet’s orbital distance (assuming we know the mass of the star)? only the Doppler technique |
all of these techniques |
Why do we say that the Doppler technique gives the planet’s "minimum mass"? The size of the Doppler shift that we detect depends on whether the planet’s orbit is tilted. |
The size of the Doppler shift that we detect depends on whether the planet’s orbit is tilted. |
How do we use velocity curves (obtained from spectroscopy) to show that some extrasolar planets are close to their host stars? The velocity curve of the host star shows periods much longer than a year. |
The velocity curve of the host star shows periods much shorter than a year. |
Which of the following orbital characteristics has NOT been observed among any known extrasolar planets? orbital speeds that are so slow that we cannot explain them |
orbital speeds that are so slow that we cannot explain them orbits that are not elliptical |
What method has detected the most extrasolar planets so far? the transit method |
the Doppler technique |
Which one of the following can the transit method tell us about a planet? its mass |
its size |
Which method could detect a planet in an orbit that is face-on to the Earth? Doppler technique |
astrometric technique |
Most extrasolar planets discovered so far most resemble terrestrial planets. |
jovian planets. |
Most known extrasolar planets are more massive than Jupiter because we do not expect smaller planets to exist. |
current detection methods are more sensitive to larger planets. |
The following four graphs show the velocities, toward and away from Earth, of four identical stars. Assume that all four stars have extrasolar planets orbiting them at the same distance, and that the velocities are inferred by measuring Doppler shifts in the spectra of the stars. Rank the graphs from left to right based on the amount of orbital Doppler shift observed in each star’s spectrum, from smallest to largest. |
Smallest Doppler shift to Largest Doppler shift: small wavelengths- small velocities to big wavelengths- large velocities |
The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Part A). Assume that all four stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the amount of time that it takes the extrasolar planet orbiting each star to complete one orbit, from shortest to longest. If you think that two (or more) of the graphs should be ranked as equal, drag one on top of the other(s) to show this equality. |
Shortest to longest amount of time: All of the velocities are equal. |
The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Parts A and B). Assume that all four identical stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the mass of the extrasolar planet that orbits the star, from smallest to largest. |
Smallest to largest mass: small wavelengths- small velocities to big wavelengths- large velocities |
Which of the following properties can be inferred from the star’s orbital period? the planet’s orbital radius |
the planet’s orbital radius |
Is it possible to determine the planet’s mass from the star’s velocity curve? yes, by measuring both the star’s orbital period and its change in velocity over the orbit |
yes, by measuring both the star’s orbital period and its change in velocity over the orbit |
Consider the planet that causes the stellar motion shown in Plot 2 (be sure you have clicked the "Plot 2" button in the lower window of the animation). What can be said about a different planet orbiting the same star with an orbital period of 500 days? The planet must be less massive. |
The planet must be closer to the star. |
Based on what we know about our own solar system, the discovery of hot Jupiters came as a surprise to scientists because these planets are __________. made of different materials than either the terrestrial or jovian planets in our solar system |
so close to their stars |
Our modern theory of solar system formation—the nebular theory—successfully accounts for all the major features of our own solar system. However, when the first hot Jupiters were discovered, their existence seemed inconsistent with the nebular theory because this theory predicts that __________. jovian planets can form only in the cold, outer regions of a solar system |
jovian planets can form only in the cold, outer regions of a solar system |
The discovery of hot Jupiters led scientists to reconsider the nebuar theory. Which of the following best explains why the nebular theory(as it stood before the discoveries of extrasolar planets) had not predicted the existence of hot Jupiters? There are no hot Jupiters in our solar system. |
There are no hot Jupiters in our solar system. |
Today, the leading hypothesis for the existence of hot Jupiters is that they formed in their outer solar systems and then migrated inward. Why did this hypothesis gain favor over alternative ideas? Computer models that simulate planetary formation show that interactions between young planets and other material in the surrounding disk can cause planetary migration. |
Computer models that simulate planetary formation show that interactions between young planets and other material in the surrounding disk can cause planetary migration. |
Assume that the migration hypothesis is the correct explanation for the hot Jupiters. In that case, the revised nebular theory looks just like the old theory, except that it now allows for the possibility of migration. Which of the following statements are consistent with this revised theory? Terrestrial planets always form in the warm, inner regions of their star system. |
Terrestrial planets always form in the warm, inner regions of their star system. Jovian planets always form in the cold, outer regions of their star system. Jovian planets can migrate inward and disrupt the orbits of terrestrial planets. |
The following images show four identical Sun-like stars and their companion planets, all traveling in circular orbits. In each case, the mass of the planet is given in Jupiter masses and the orbital distance is given in Astronomical Units (AU). Rank each case based on the strength of the gravitational force exerted by the extrasolar planet on its central star, from weakest to strongest. If you think that two (or more) diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Not to scale) |
Weakest to strongest: One Jupiter Mass 2AU, Four Jupiter Masses 2 AU/One Jupiter Mass 1 AU (both are equal), Two Jupiter Masses 1 AU. |
The following figures show four identical Sun-like stars and their companion planets. Each planet’s orbital distance is given in Astronomical Units (AU); note that in this case, all four planets have the same mass. Rank the extrasolar planets based on the amount of time it takes each to complete one orbit, from shortest to longest. (Not to scale) |
Shortest to longest time: 1 AU, 1.5 AU, 2 AU, 2.5 AU |
The following images show the set of four stars and planets as in Part B. Imagine that an Earth-based observer could see the motion of each of the stars edge-on. Rank each star based on the amount of Doppler shift we’d see in its spectrum as it moves in response to the gravitational tug of its planet, from smallest to largest. (Not to scale) |
Smallest to largest Doppler shift: 2.5 AU, 2 AU, 1.5 AU, 1 AU |
How is the planet 51 Pegasi different from Jupiter? much closer to its star |
much closer to its star |
Which detection method can be used on a backyard telescope with a CCD system? Doppler technique |
transits |
Compare this density to the average densities of Saturn (0.7g/cm3) and Earth (5.5g/cm3). Is the planet terrestrial or jovian in nature? jovian planet |
jovian planet |
Which of two masses, if either, is larger. The planet with the longer period is the larger one. |
The planet with the longer period is the larger one. |
Each item describes a characteristic that applies to one of the three planet-detection methods shown following. Match the items to the correct planet-finding method. |
Doppler method: -used for most of the first 200 extrasolar planet detections -currently best-suited to find Jupiter-sized extrasolar planets orbiting close to their stars Transit method: -planet-detection strategy of NASA’s Kepler Mission -allows for the extrasolar planet’s radius to be determined -this method was first to identify Earth-sized extrasolar planets -Can potentially detect planets in only a few percent of all planetary systems -looks for very slight, periodic dimming of a star Astrometric method: -measures precise changes in a star’s position in the sky, in fractions of arcseconds |
1. The __________ was used to find a Jupiter-sized planet through careful measurements of the changing position of a star. |
astrometric technique |
2. Discovering planets through the __________ requires obtaining and studying many spectra of the same star. |
Doppler technique |
3. The __________ is currently searching for planet transits around some 100,000 stars. |
Kepler mission |
4. The ___________ is used to find extrasolar planets by carefully monitoring changes in a star’s brightness with time. |
transit technique |
5. The ___________ is being designed to measure very small changes in stellar positions, which should allow it to discover many extrasolar planets. |
GAIA Astrometry Mission |
6. Proposed plans for the _____________ would someday provide us with the first actual images and spectra of terrestrial worlds orbiting other stars. |
Terrestrial Planet Finder mission |
Why do scientists say that evolution is a "theory"? because it is supported by only a small amount of evidence |
because it explains a great deal about life and is supported by an enormous body of evidence |
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 all species ever to exist that we currently are aware of |
the fraction of planets with civilizations at the present time (as opposed to only in the past or future) |
Why don’t we expect to find life on planets orbiting high-mass stars? The lifetime of a high-mass star is too short. |
The lifetime of a high-mass star is too short. |
We have sent several spacecraft on trajectories that will ultimately take them into interstellar space (Pioneer 10 and 11, Voyager 1 and 2, New Horizons). How long will it take these spacecraft to travel as far as the nearest stars? a few hundred years |
tens of thousands of years |
The graph above shows how a star’s orbital speed varies with time due to the gravitational tug of an orbiting planet. These data were obtained by measuring __________.
the precise brightness of the star divided by the precise brightness of the planet |
the precise wavelengths of spectral lines in the spectrum of the star |
The graph above shows how a star’s orbital speed varies with time due to the gravitational tug of an orbiting planet. Based on these data, the planet’s orbital period is about: 2 days |
4 days |
This diagram 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: the orbital distance of Saturn |
the fact that large, icy objects orbit the Sun in the Kuiper belt |
The four graphs below show Doppler data for four different stars. Assume that all four stars have planetary systems oriented the same way toward Earth, so that the data can be compared fairly. Which graph reveals the existence of a planet with the greatest mass? Graph 1 |
Graph 2 |
The four graphs below show Doppler data for four different stars. Assume that all four stars have planetary systems oriented the same way toward Earth, so that the data can be compared fairly. Which graph reveals the existence of a planet with the longest orbital period? Graph 1 |
Graph 4 |
This diagram represents a star with an orbiting planet that, as seen from Earth, periodically transits across the face of the star and disappears behind the star. If you measure the brightness of this system, at which point would it be brightest? 1 |
1 |
Each dot on this graph represents an extrasolar planet; the green dots (labeled) represent planets of our own solar system. What can you conclude about the extrasolar planets shown on this graph? Most of the planets orbit in star systems that have at least three planets. |
Many of these planets have orbits that differ significantly from perfect circles. |
This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet with the greatest mass? 1 |
4 |
This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet with the greatest density? 1 |
2 |
This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet has about the same composition as Earth but is larger in both size and mass? 1 |
3 |
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 in the sky, with the same ellipse repeated every night. |
It causes the Sun to move in a small ellipse with an orbital period of about 12 years. |
Why is it so difficult to take pictures of extrasolar planets? Their light is overwhelmed by the light from their star. |
Their light is overwhelmed by the light from their star. |
Suppose you are using the Doppler technique to look for planets around another star. What must you do? Carefully examine a single spectrum of an orbiting planet. |
Compare many spectra of the star taken over a period of many months or years. |
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 |
a massive planet that is close to its star |
Suppose a planet is discovered by the Doppler technique and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________. its precise mass |
its rotation period |
The transit method allows us in principle to find planets around __________. only stars of about the same mass and size as our Sun |
only a small fraction of stars that have planets |
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. |
The planet must be closer to the star than Earth is to the Sun. |
Which of the following will allow you to learn something about a transiting planet’s atmospheric composition? Use the Doppler method to study the planet throughout a cycle from one transit to the next. |
Compare spectra obtained before and during an eclipse. |
Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that ________. small planets are more difficult to detect than larger planets |
small planets are more difficult to detect than larger planets |
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true? Planets always tend to orbit their star in the same direction and approximately the same plane. |
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation. |
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? Planets at such distances are probably very low in mass. |
We have not yet been searching for planets at such distances for a long enough time. |
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. |
These planets migrated inward after being born on orbits much farther from their stars. |
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 stuck around for an unusually long time after the formation of jovian planets. |
Our solar nebula must have been blown into space shortly after the formation of the jovian planets. |
When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars? In just a few years, through analysis of observations by the James Webb Space Telescope. |
In a decade or two, through space observatories now in the early planning stages. |
Listed below are several geological and biological events in Earth’s history. Rank the events in the order in which they occurred, from first to last. |
First to last to occur: giant impact forms moon, end of heavy bombardment, early life (based on fossil evidence), oxygen build-up in atmosphere, animals colonize land, earliest mammals, dinosaurs go extinct |
Earth was born about 4.5 billion years ago. According to current estimates, approximately how long after Earth’s formation did the Moon form? |
a few tens of millions of years later. |
The oldest fossil evidence of life dates to about __________ ago. 100 million years |
3.5 to 4 billion years |
Dinosaurs went extinct, probably because of an impact, about __________ ago. 5 million years |
65 million years |
Listed below are the names, spectral types (in parentheses), and approximate masses of several nearby main-sequence stars. Rank the stars based on the distances to their habitable zones (from the central star), from shortest to longest. |
Smallest to largest distance: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica |
Consider again the same set of five stars. This time, rank the stars based on the size (width) of their habitable zones, from smallest to largest. |
Smallest to largest: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica |
Imagine that each of the five stars is orbited by a terrestrial planet at a distance of 1 AU (Earth’s distance from the Sun). Rank the stars based on the planet’s expected surface temperature (not including any greenhouse effect), from lowest to highest. |
Lowest temperature to highest temperature: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica |
To understand the difference between worlds that are potentially habitable and those that probably are not. |
Likely to be habitable: -underground on Mars -moon with atmosphere orbiting jovian planet 1 AU from 1 MSun star -subsurface ocean on Europa Unlikely to be habitable: -surface of Mars -volcanos on Io -surface of terrestrial planet 10 AU from 0.5 MSun star |
Which statement explains the observations that make it seem possible that Mars could have life underground? We have detected subsurface wells of liquid water in equatorial regions of Mars. |
We have detected water ice on Mars, and Mars still has some volcanic heat. |
In Part A you found that the terrestrial planet 10 AU from a 0.5MSun star is unlikely to be habitable. Could this planet be habitable if it were in a different orbit around its star? Yes, if it had an eccentric orbit that sometimes brought it within 0.01 AU of its star. |
Yes, but it would have to be less than 0.5 AU from its star. |
As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________. increases / increases |
increases / increases |
Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case? Only Mercury would be in the Sun’s habitable zone. |
Only Mercury would be in the Sun’s habitable zone. |
Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why? The expected lifetime of a massive star is too short to allow for the evolution of complex life |
The expected lifetime of a massive star is too short to allow for the evolution of complex life |
1. High-mass main-sequence stars have a more distant and wider ________ than low-mass stars. |
habitable zone |
2. Sky surveys looking for radio signals generated by technology are part of the ______________. |
search for extraterrestrial intelligence |
3. The _________ is designed as a way of estimating the number of intelligent civilizations in the Milky Way. |
Drake equation |
4. The notion that living organisms with advantages that give them greater reproductive success (in some local environment) will survive while others perish is an example of what Darwin called _________. |
natural selection |
5. One of the key premises for the _________ is that living organisms are able to produce far more offspring than their environment can support. |
theory of evolution |
6. The different time periods of the ______________ are defined by changes in fossils found from those time periods. |
geological time scale |
7. Incoming ultraviolet light from the Sun can cause a __________ in a living organism’s DNA that can affect its ability to survive and reproduce. |
mutation |
Astronomy Test 3
Share This
Unfinished tasks keep piling up?
Let us complete them for you. Quickly and professionally.
Check Price