All of Astronomy Chapter 6 HW

Part c) As discussed in the Extraordinary Claims box, when the giant impact idea was first proposed, it was generally thought to be so unlikely that it wasn't seriously considered until decades later, after the Apollo missions to the Moon. What key piece of scientific understanding was missing that made it seem so unlikely when first proposed?

An understanding of the number and size of leftover planetesimals in the early solar system. Submit

Part b) What fraction of the original uranium-235 should be left after 3.5 billion years?

1/32

Part j- Quiz Question 10) 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?

2 billion years

Part d) Suppose you find a rock and measure that 12.5% of the original uranium-235 still remains it, while the other 87.5% has decayed into lead-207. About how old is the rock?

2.1 billion years

29: Problem 6.34 Part a) About how old is the solar system?

4.5 billion years

Part d) The verdict at the end of the Extraordinary Claims box says "Likely correct, though may never be possible to prove definitively." In the context of models, which of the following best explains this verdict?

A model that precisely reproduces major characteristics of the Moon would seem likely correct, but we can't go back in time to see that it actually happened that way.

4: Pre-lecture Narrated Figure: The Formation of the Solar System Part a) When did the objects that we now see as asteroids and comets form in the solar system?

After solid particles condensed from the gas but before the planets finished forming.

Part d) 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?

All the planets orbit the Sun in the same direction and in nearly the same plane.

Part d- Quiz Question 4) What planet is this, and how do you know?

Saturn, because of its colors and bright, wide rings.

Part b) 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.

20: Problem 6.25 Part a) How many of the planets orbit the Sun in the same direction as Earth does?

all

Part c) Where would you expect terrestrial planets to form in the solar nebula?

anywhere between the innermost regions (within about the inner 0.3 AU) and the frost line

Part h) Suppose the solar nebula had been too warm for ices to condense anywhere. If a planet had still formed at Jupiter's location, it most likely would have

been similar in composition to Earth, with a much smaller mass than the real Jupiter.

26: Problem 6.30 Part a) Which lists the major steps of solar system formation in the correct order?

collapse, condensation, accretion

27: Problem 6.31 Part a) Leftover ice-rich planetesimals are called

comets.

25: Problem 6.28 Part a) Which of the following did not occur during the collapse of the solar nebula?

concentrating denser materials nearer the Sun

32: Chapter 6 Visual Quiz Part a- Quiz Question 1) In this perspective view of the solar system, the sizes of the planets are ___________ relative to the sizes of their orbits.

exaggerated about 1,000 times

23: Problem 6.26 Part a) Planetary orbits in our solar system are:

fairly circular and in the same plane.

Part c) Which of the following is thought to explain many of the "exceptions to the rules" of our solar system?

giant impacts

21: Problem 6.29 Part a) What is Jupiter's main ingredient?

hydrogen and helium Submit

24: Problem 6.27 Part a) The composition of the solar nebula was 98%

hydrogen and helium. Submit

Part b) What substances existed as solid flakes within the innermost regions (within about the inner 0.3 AU) of the solar system before planets began to form?

none

Part b) A rock that contains seven times as much argon-40 as potassium-40. Express your answer using three significant figures.

t = 3.75×10^9 years

Part d) 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 _________.

this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula Submit

30: Visual Skills Check 6.1 Part a) Compare the graph in (Figure 1) to (Figure 2), which shows the decay of potassium-40. Which element is more radioactive (undergoes radioactive decay more quickly)?

uranium-235

Part f) Suppose the solar nebula had cooled much more before the solar wind cleared away the remaining gas. In that case, the terrestrial planets likely would have ended up

with a higher abundance of hydrogen compounds and larger size.

6: Ranking Task: Orbital Distance, Mass, and Radius of Planets Part a) 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: -Pluto -Saturn -Jupiter -Mars -Earth -Mercury

16: Ranking Task: Matter in the Solar System Part a) 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 Abundance: -hydrogen and helium gas - hydrogen compounds -rock -metals

Part h- Quiz Question 8) What is the significance of this image?

It shows an actual disk of material orbiting another star, providing strong evidence the planets really do form in such disks.

Part b) Which of the following statements was true beyond the frost line (but not interior to it)?

It was cold enough for hydrogen compounds to condense into ices.

Part c) 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 Radius: -Sun -Jupiter -Earth -Mars -Mercury -Pluto

Part b) 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 Time: -Neptune -Jupiter -Mars -Earth -Mercury

Part b) We expect a scientific theory to be able to make predictions that can be tested. Which of the following is a prediction of the nebular theory that has been verified by observations?

Many stars should have planets

Part b- Quiz Question 2) What planet is shown in this photo?

Mars

13: Ranking Task: Relative Time Line for Formation of the Solar System Part a) 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 stage: -large cloud of gas and dust -contraction of solar nebula -condensation of solid particles -accretion of planetesimals -clearing the solar nebula

Part b) 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 Mass: -Sun -Jupiter -Earth -Mars -Mercury -Pluto

Part b) 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 Temperature: -metals -rock -hydrogen compounds -hydrogen and helium gas

Part c) 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 number: -Jupiter -Mars -Earth -Mercury

7: Ranking Task: Planet Temperature, Orbital Period, and Number of Moons Part a) 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: -Mercury -Earth -Mars -Jupiter -Neptune

Part e) 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?

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.

Part c) Now consider the second major feature (two types of planets). Which of the following statements are true for the terrestrial and Jovian planets in our solar system? Select all that apply.

-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. -Jovian planets are larger in mass than terrestrial planets.

9: Vocabulary in Context: Basic Planet Facts Part a) Match the words in the left-hand column to the appropriate blanks in the sentences in the right-hand column. Use each word only once.

1."Uranus" has a rotational axis that is tilted so much it lies nearly in the plane of its orbit. 2. "Venus" is the planet with the highest average surface temperature. 3. The planet that orbits closest to the Sun is "Mercury" 4. The only rocky planet to have more than one moon is "Mars" 5. "Jupiter" is the jovian planet that orbits closest to the Sun. 6. Most of the surface of "Earth" is covered with liquid water. 7. "Neptune" is about 30 times as far from the Sun as our own planet. 8. The planet with the lowest average density is "Saturn"

12: Vocabulary in Context: Solar System Formation Part a) Match the words in the left-hand column to the appropriate blanks in the sentences in the right-hand column. Use each word only once.

1.Our solar system was created by the gravitational collapse of the "solar nebula." 2. Our Moon was most likely formed by a collision between Earth and a Mars-sized "planetesimal". 3. The first few hundred million years of the solar system's history were the time of the "heavy bombardment", during which Earth suffered many large impacts. 4. Mars was formed by the "accretion" of smaller objects. 5. 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". 6. Ice can form from a gas through the process of "condensation". 7. Hydrogen compounds in the solar system can condense into ices only beyond the "frost line". 8. "Radiometric dating" allows us to determine the age of a solid rock.

Part b) Suppose you have a rock that, when it solidifies, contains 1 microgram of a radioactive isotope. How much of this isotope remains after five half-lives?

1/32 microgram

Part c) Approximately what is the half-life of uranium-235?

700 million years

Part c) 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?

Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole. Submit

15: Process of Science: Testing the Nebular Theory Part a)Sort the following hypothetical discoveries into the appropriate bins as follows: -Consistent with theory: The statement describes a discovery that we could reasonably expect to find if the nebular theory is correct. -Not consistent with theory: The statement describes a discovery that would force us to modify or discard the nebular theory.

Consistent with Theory: -Beyond its Jovian planets, a star has two ice-rich objects as large as Mars. -A star has 20 planets. -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. Not Consistent with Theory: -A star has 9 planets, but none orbit in close to the same plane. -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.

Part c) 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: -hydrogen compounds -rock -metals

Part c) You find a mysterious rock on the ground and determine that 60% of its uranium-235 has been converted into lead-207. What is the most likely origin of the rock, based on its radiometric age?

It's a volcanic rock nearly a billion years old.

28: Problem 6.32 Part a) What's unusual about our Moon?

It's surprisingly large relative to the planet it orbits.

Part d) Based on what the nebular theory tells us about the formation of our own solar system, what does the theory predict for the possibility of other planetary systems?

Planetary systems should be common.

Part i- Quiz Question 9) This diagram represents the solar nebula early in its history, and shows the location of the frost line. Suppose you discover an object that is made of metal, rock, and ice. In which region of the solar system did it form?

Region 4

19: Process of Science — Extraordinary Claims: A Giant Impact Made Our Moon Part a) The statements below are all true. Some of them represent important reasons why the giant impact hypothesis for the Moon's formation is taken seriously, and some of them are not relevant to deciding between this and other hypotheses. Sort the statements into the correct bin according to whether or not they provide important support to the giant impact hypothesis.

Supports Giant Impact Hypothesis: -Moon's composition is similar to Earth's mantle -Moon has a low proportion of easily vaporized ingredients -Models indicate early solar system had Mars-size leftover planetesimals True but Not Relevant to Giant Impact Hypothesis: -Moon lacks active volcanoes -Moon has synchronous rotation (keeps same face to Earth) -Moon's distance is gradually increasing

14: Sorting Task: Formation of Terrestrial and Jovian Planets Part a) Each of the following statements applies either to the formation of terrestrial planets or of jovian planets (but not both), based on our current theory of solar system formation. Drag the statements into the appropriate bin.

Terrestrial Planets: -accreted from planetesimals of rock and metal -surfaces dramatically altered during the heavy bombardment Jovian Planets: -formed in a region of the solar system with lower orbital speeds -ejected icy planetesimals that are now Oort cloud comets -large moons formed in surrounding disks of material -accreted from icy planetesimals -formed in regions cold enough for water to freeze

8: Sorting Task: Characteristics of Terrestrial and Jovian Planets Part a) Listed following are characteristics that can identify a planet as either terrestrial or jovian. Match these to the appropriate category. Consider only the planets of our own solar system.

Terrestrial Planets: -located within the inner solar system -small size -solid, rocky surface Jovian Planets: -low average density -primarily composed of hydrogen, helium, and hydrogen compounds -extensive ring systems -numerous orbiting moons

Part g- Quiz Question 7) 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

5: Pre-lecture Narrated Figure: Radiometric Dating Part a) What do we mean when we say that a nucleus undergoes radioactive decay?

The number of protons or neutrons (or both) in the nucleus changes.

Part b) Consider only the first major feature, which concerns 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 each born in a separate, random event.

2: Pre-lecture Video: Major Features of Our Solar System Part a) Which one of the following is not one of the four major features of the solar system?

The solar system contains eight planets plus dwarf planets (such as Ceres, Pluto, and Eris).

22: Problem 6.33 Part a) Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun?

Venus and Uranus are exceptions. Submit

Part f- Quiz Question 6) In this photograph, the large and bright object in the sky is _______________.

a comet

Part b) As the solar nebula collapsed, it became a disk because

collisions between particles made the particles go in more-or-less the same direction. Submit

Part d) 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 predict __________.

general characteristics of other solar systems

Part c) The inner planets are small and rocky and the outer planets are mostly large and gaseous because

hydrogen compounds are more abundant than rocks and metals so that beyond the frost line the gravity of large ice planetesimals could capture the abundant light gases. Submit

Part e) As the solar nebula collapsed under its own gravity,

it heated up and spun up.

Part c) The "giant impact hypothesis" refers to the idea that ___________.

our Moon formed when a Mars-size object collided with the young Earth.

Part c) 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 __________.

planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane

Part d) The temperature of the protoplanetary disk allowed

rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds to freeze only in the outer region.

Part d) The Jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________.

rocks, metals, and ices

31: Problem 6.46 Part a) A rock that contains equal amounts of potassium-40 and argon-40. Express your answer using three significant figures.

t =1.25×10^9 years

18: Key Concept: Understanding the Nebular Theory Part a) Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, the nebular theory predicts that a cloud will rotate rapidly once it shrinks to a relatively small size. What physical law explains why a collapsed cloud will rotate rapidly?

the law of conservation of angular momentum

Part b) 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

11: Formation of the Solar System Tutorial Part a) The planets in our solar system are thought to have come from

the same cloud of gas and dust in which the Sun formed.

1: Pre-lecture Overview: Our Planetary System Part A) Drag the correct object from the left to the statement that goes with it at the right. Use each choice only once.

-Earth- has a single moon that is surprisingly large compared to its planet. -Eris- is similar in size to Pluto and also considered a dwarf planet. -Mars- has no surface liquid water today, but shows clear evidence of such water in the distant past. -Mercury- has a greater difference in temperature between its day and night sides than any other world. -Jupiter- has a famous storm known as the Great Red Spot. -Pluto- was studied up close in 2015 by the New Horizons spacecraft. -The Sun- generates energy deep in its core through the fusion of hydrogen into helium -Uranus- has an axis tilt that gives it very extreme seasons. -Venus- has a surface hot enough to melt lead as a result of an extremely strong greenhouse effect. -Saturn- is orbited by at least two geologically active moons: Titan and Enceladus. -Neptune- has a large moon, Triton, that almost certainly once orbited the Sun independently.

Part e) While we may never be able to prove that our Moon really formed in a giant impact, which of the following would give scientists greater confidence that the model is correct? Select all that apply.

-Finding evidence that other giant impacts occurred in our solar system, with a total number of impacts consistent with what models of solar system formation lead us to expect. -Observing evidence of recent giant impacts in other solar systems that are currently in the process of formation. -Creating more sophisticated models of the giant impact that correctly predict many detailed characteristics of the Earth and Moon. Submit

10: Process of Science: What Should a Theory of Solar System Formation Explain? Past a) For the purposes of seeking a theory to explain the formation of the solar system, we identify four major features of our solar system. Which of the following represent these four major features? Select four statements to represent the four features.

-Large bodies in the solar system have orderly motions. -Swarms of asteroids and comets populate the solar system. -Several exceptions to the general trends stand out. -Planets fall into two major categories (terrestrial and jovian).

Part f) 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?

-Many extra-solar planets should fall into the terrestrial or Jovian categories. -Planetary systems should generally have all planets orbiting in nearly the same plane. -Planetary systems should be common. -Jovian planets always form farther from their star than terrestrial planets. Submit

Part b) Consider the three items from Part A that are not relevant to the giant impact hypothesis. As you'll learn in later chapters, the lack of volcanoes is a result of the Moon's relatively small size. But what explains the other two items — the Moon's synchronous rotation and gradually increasing distance from Earth?

Both are results of tidal interactions between the Moon and Earth.

Part c) 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 __________.

all the planets formed in a rotating, disk-shaped nebula

17: Visual Activity: Condensed Materials in Different Regions of the Disk of the Forming Solar System Part a) What substances were found in the innermost regions (within about the inner 0.3 AU) of the solar system before planets began to form?

rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form Submit

Part g) If the solar nebula initially had no angular momentum,

there would not be any planets orbiting the Sun. Submit

Part f) In the context of studying major bodies of our solar system, what category of object does our Moon best fit?

Terrestrial world

Part e- Quiz Question 5) Which pair of photos shows Earth correctly scaled in comparison to Jupiter?

(Earth is the smallest out of the options) picture link: https://session.masteringastronomy.com/problemAsset/2640064/3/06_06a_VQ.jpg

Part c- Quiz Question 3) Which pair of photos shows Earth correctly scaled in comparison to the Sun?

(the Earth is the smallest) picture link: https://session.masteringastronomy.com/problemAsset/2640064/3/06_02a_VQ.jpg

Part b) Consider the first major feature (orderly motions). Which of the following correctly describe patterns of motion in our solar system? Select all that apply.

- Planets have nearly circular orbits. -All the planets orbit the Sun in nearly the same plane. - The Sun and most of the planets rotate in the same direction that the planets orbit

3: Pre-lecture Overview: Formation of the Solar System Part a) What are four key features of our solar system that any theory of solar system formation must be able to explain? Select exactly four responses.

-Planets fall into two major categories. -There are a few notable "exceptions to the rules." -There are clear patterns to the rotation and orbits of large bodies in the solar system. -There are vast numbers of asteroids and comets.

Part e) All the following statements are true. Which of them are considered to be "exceptions" to the general trends described by the first three major features of the solar system? Check all that apply.

-Venus rotates in a direction opposite to the rotation of the other terrestrial planets. -Our Moon has a diameter more than 1/4 the diameter of Earth. -Uranus rotates with an axis tilt that lies nearly in the ecliptic plane.

Part d) 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 __________. Select all that apply.

-the Kuiper belt -the Oort cloud -the asteroid belt