Chapter 7 Review

13. [2pt]You find a meteorite 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 the graph of the previous question, about how old is the rock? A) 2.5 billion years B) 2 billion years C) 3 billion years D) 1.25 billion years E) 1 billion years

B) 2 billion years

14. [1pt]According to modern scientific dating techniques, approximately how old is the solar system? A) 5 000 years B) 4.5 billion years C) 13.8 billion years D) 4.5 million years E) 13.8 million years

B) 4.5 billion years

1. [1pt]How many planets orbit the Sun in the same direction that Earth does? A) A few. B) All. C) About half. D) Only one. E) Most.

B) All.

21. [2pt]Which of the following best explains why we can rule out the idea that planets are usually formed by near-collisions between stars? A) A near collision might have created planets, but it could not have created moons, asteroids, or comets. B) Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars. C) Studies of the trajectories of nearby stars relative to the Sun show that the Sun is not in danger of a near-collision with any of them. D) A near collision should have left a trail of gas extending out behind the Sun, and we see no evidence of such a trail.

B) Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars.

24. [2pt]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? A) Both types of planet begun with planetesimals growing through the process of accretion, but only the jovian planets were able to capture hydrogen and helium gas from the solar nebula. B) The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal. C) The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it. D) Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets.

B) The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.

19. [2pt]In the same evolutionary sequence of a collapsing gas cloud shown in the previous question, what law explains why the center of the cloud becomes so much hotter as the cloud shrinks in size? A) Kepler's third law. B) The law of conservation of energy. C) The universal law of gravitation. D) The law of conservation of angular momentum. E) Newton's second law of motion.

B) The law of conservation of energy.

25. [2pt]What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)? A) The locations of various materials in the solar nebula. B) The temperatures at which various materials will condense from gaseous form to solid form. C) The amounts of energy required to ionize various materials. D) The atomic mass numbers of various materials.

B) The temperatures at which various materials will condense from gaseous form to solid form.

23. [2pt]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? A) Hydrogen and helium are produced in stars by nuclear fusion. B) All the other elements escaped from the solar nebula before the Sun and planets formed. C) Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young. D) All the other elements were swept out of the solar system by the solar wind.

C) Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young.

17. [2pt]The images below shows a 'debris disk' around two nearby stars. On the images, the light from the central bright star has been masked for better contrast. What is the significance of this type of 'debris disk'? A) It shows that stars can be encircled by disks that are enormous in size, sometimes extending halfway to other nearby stars. B) It shows that the disks that encircle stars are sometimes split into two pieces, with one on each side of the star. C) It shows that stars really can be surrounded by flattened disks of dust and gas. D) It proves that planets form in disks of dust and gas that surround stars. E) That stars can produce powerful jets of debris.

C) It shows that stars really can be surrounded by flattened disks of dust and gas.

35. [2pt]What do we mean by the period of heavy bombardment in the context of the history of our solar system?A) The time during which heavy elements condensed into rock and metal in the solar nebula. B) The time before planetesimals finished accreting into planets, during which many growing planetesimals must have shattered in collisions. C) The first few hundred million years after the planets formed, which is when most impact craters were formed. D) The period about 65 million years ago when an impact is thought to have led to the extinction of the dinosaurs.

C) The first few hundred million years after the planets formed, which is when most impact craters were formed.

28. [2pt]According to our present theory of solar system formation, how did Earth end up with enough water to make oceans? A) The water was mixed in the other materials in the planetesimals that accreted at our distance from the Sun. B) Earth formed in the relatively narrow region of the solar nebular in which liquid water was plentiful. C) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars. D) The water was formed by chemical reactions among the minerals in the Earth's core.

C) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.

2. [2pt]In essence, the nebular theory holds that _______. A) nebulae are clouds of gas and dust in space. B) the nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our Sun and another star. C) our solar system formed from the collapse of an interstellar cloud of gas and dust. D) planets have formed in a still unclear, nebulous way. E) each planet formed from the collapse of its own separate nebula.

C) our solar system formed from the collapse of an interstellar cloud of gas and dust.

5. [3pt]You have three tries for this question. The materials that made up the solar nebula can be categorized into the four general types listed below. Rank these materials based on the temperature at which each would condense into a solid, from the highest to lowest. Note: For a substance that does not condense at all, rank it as very low temperature. A) Rocks B) Hydrogen compounds C) Metal D) Hydrogen and Helium gas

CABD

4. [2pt]You have three tries for this question. The materials that made up the solar nebula can be categorized into the four general types listed below. Rank these materials based on their abundance in the solar nebula, from the highest to the lowest. A) Rocks B) Metal C) Hydrogen and Helium gas D) Hydrogen compounds

CDAB

3. [3pt]You have three tries for this question. According to our current theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? Select ALL that apply. A) Nuclear fusion produced heavy elements to make the jovian planets. B) Central temperatures rose to more than a trillion Kelvin. C) It got hotter. D) Its rate of rotation increased. E) Its mass increased. F) It flattened into a disk. G) Its gas clumped up to form the terrestrial planets.

CDF

20. [2pt]The diagram below 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? A) 3 B) 2 C) None of them D) 4 E) 1

D) 4

32. [2pt]According to modern science, what was the approximate chemical composition of the solar nebula? A) Roughly equal proportions of hydrogen, helium, water, and methane. B) 50 percent hydrogen and helium, 50 percent everything else C) 98 percent hydrogen, 2 percent helium D) 98 percent hydrogen and helium, 2 percent everything else E) 78 percent nitrogen, 21 percent oxygen, and 1 percent of everything else

D) 98 percent hydrogen and helium, 2 percent everything

16. What does this photo below show? A) A nice abstract painting. B) Stars viewed through the atmosphere of Venus. C) A galaxy much like our Milky Way Galaxy. D) An interstellar cloud that is in the process of giving birth to thousands of star systems. E) An interstellar cloud that probably looks almost identical to the way the solar nebula looked about 4.5 billion years ago.

D) An interstellar cloud that is in the process of giving birth to thousands of star systems.

27. [2pt]According to present understanding, which of the following statements about the solar wind is not true? A) It consists of charged particles blown off the surface of the Sun. B) It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today. C) It swept vast amounts of gas from the solar nebula into interstellar space. D) It is even stronger today than it was when the Sun was young.

D) It is even stronger today than it was when the Sun was young.

18. [2pt]This evolutionary sequence 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? A) Kepler's third law. B) The law of conservation of energy. C) The universal law of gravitation. D) The law of conservation of angular momentum. E) Newton's second law of motion.

D) The law of conservation of angular momentum.

9. [2pt]What do we mean by the frost line when we discuss the formation of planets in the solar nebula? A) It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds. B) It is the transition line within the solar system where snow can form at the surface of the planet. C) It is the altitude in a planet's atmosphere at which snow can form. D) It is another way of stating the temperature at which water freezes into ice. E) It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

E) It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

10. [2pt]What is the 'giant impact hypothesis' for the origin of the Moon? A) The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth. B) The Moon formed just like Earth, from accretion in the solar nebula. C) The Moon was originally in orbit in the asteroid belt, got out of its orbit due to Jupiter's tidal forces, and finally got captured by Earth. D) The Moon formed when two gigantic asteroids collided with one another. E) The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.

E) The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.

33. [2pt]The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from? A) They have been present in the universe since its birth. B) They were produced by gravity in the solar nebula as it collapsed. C) They were produced in the protosun, by nuclear fusion. D) They were made by chemical reactions in interstellar gas. E) They were produced by stars that lived and died before our solar system was born.

E) They were produced by stars that lived and died before our solar system was born.

11. [3pt]You have 3 tries for this question. Match the missing [blank] words to the correct sentence about the solar system formation. (If the first corresponds to B, and the next 4 to C, enter BCCCC) .1) [blank] allows us to determine the age of a solid rock. A. heavy bombardment 2) The first few hundred million years of the solar system 19s history were the time of the [blank], during which Earth suffered many large impacts. B. frost line 3) The era of planet formation ended when the remaining hydrogen and helium gas of the solar nebula was swept into interstellar space by the [blank]. C. solar nebula 4) Hydrogen compounds in the solar system can condense into ices only beyond the [blank]. D. accretion 5) Mars was formed by the [blank] of smaller objects. E. solar wind 6) Our solar system was created by the gravitational collapse of the [blank]. F. radiometric dating

FAEBDC

37. [3pt]You have 3 tries for this quesiton. Indicate whether the following statements are characteristics of the formation of terrestrial planets or of jovian planets. Match these to the appropriate category.(Select T-Terrestrial, J-Jovian. If the first is T and the rest J, enterTJJJJ). A) accreted from icy planetesimals B) formed in regions cold enough for water to freeze C) large moons formed in surrounding disks of material D) surfaces dramatically altered during the heavy bombardment E) formed in a region of the solar system with lower orbital speeds F) accreted from planetesimals of rock and metals G) ejected icy planetesimals that are now Oort cloud comets

JJJTJTJ

15. [4pt]Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 7 years. How much of the substance will remain after 18 years pass?

0.168237524079044

22. [2pt]This simulation snapshot shows an object colliding with early Earth. What is thought to have happened as a result of such collision? A) It blasted away debris that then accreted in Earth orbit to form the Moon. B) The impact changed Earth's orbit from on which life would have been unlikely to our current orbit in which life flourishes. C) The current Earth would have been 10 times bigger without this impact. D) It lead to the extinction of dinosaurs. E) The impact released the heat that allowed Earth to undergo differentiation.

A) It blasted away debris that then accreted in Earth orbit to form the Moon.

30. [2pt]Why are terrestrial planets denser than jovian planets? A) Only dense materials could condense in the inner solar nebula. B) Gravity compresses terrestrial planets to a higher degree, making them denser. C) The Sun's gravity gathered dense materials into the inner solar system. D) Actually, the jovian planets are denser than the terrestrial planets.

A) Only dense materials could condense in the inner solar nebula.

12. [3pt]What can you conclude about studying this graph below? A) Potassium-40 has a half-life of 1.25 billion years. B) Argon-40 has a half-life of 1.25 billion years. C) Both potassium-40 and argon-40 have half-lives of 1.25 billion years. D) It takes 5 billion years to turn potassium-40 into argon-40.

A) Potassium-40 has a half-life of 1.25 billion years.

29. [2pt]What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits? A) Some moons have orbits that are 'backwards' (compared to their planet's rotation) or highly inclined to their planet's equator. B) Astronomers have observed moons being captured. C) Some moons are surprisingly large in size. D) Some moons have a composition that differs from the composition of the planets.

A) Some moons have orbits that are 'backwards' (compared to their planet's rotation) or highly inclined to their planet's equator.

34. [2pt]What do we mean by accretion in the context of planet formation? A) The growth of planetesimals from smaller solid particles that collided and stuck together B) The growth of the Sun as the density of gas increased in the center of the solar nebula C) The formation of moons around planets D) The solidification of ices, rocks, and metal from the gas of the solar nebula

A) The growth of planetesimals from smaller solid particles that collided and stuck together

36. [3pt]You have three tries for this question. Provided the following stages that occurred during the formation of our solar system, rank these stages based on when they occurred, from first to last. A) large cloud of gas and dust. B) condensation of solid particles. C) contraction of solar nebula. D) accretion of planetesimals. E) clearing the solar nebula.

ACBDE

31. [2pt]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? A) Gravity was too weak to allow asteroids to form in this part of the solar system. B) 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. C) All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter. D) It was too hot for asteroids to form in this part of the solar system.

B) 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.

8. [2pt]The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of _______. A) mainly hydrogen and helium gases. B) rocks, metals, and ices. C) rocks, metals ices, and hydrogen and helium gases. D) only ices. E) only rocks and metals.

B) rocks, metals, and ices.

6. [3pt]You have 3 tries for this question. Match the FROZEN substance listed below to its proper location within the disk of the forming solar system. (If the first corresponds to B, and the next 2 to C, enter BCC). 1) Hydrogen Compounds A. not in the disk 2) Hydrogen and Helium B. outer disk (beyond frost line at 3.5AU) 3) Metals and Rocks C. cannot freeze D. inner disk (within 0.3AU)E. middle disk (0.3-3.5AU)

BCE

26. [2pt]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? A) The meteorites sizes are just what we'd expect if metal and rock condensed and accreted as our theory suggests. B) Their overall composition is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium. C) Their appearance and composition matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals. D) The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.

D) The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.

7. [2pt]Where would you expect terrestrial planets to form in the solar nebula? A) anywhere except beyond the frost line. B) anywhere outside 0.3AU. C) anywhere outside the frost line. D) anywhere between 0.3AU and the frost line. E) within the inner 0.3AU.

D) anywhere between 0.3AU and the frost line.