ASTR Chapter 8 – Flashcards

1) What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium? A) 0 percent B) 0.1 percent C) 2 percent D) 20 percent E) 80 percent

2) Where did the elements heavier than hydrogen and helium come from? A) They were produced in the Big Bang. B) They evolved from hydrogen and helium shortly after the Big Bang. C) They were produced inside stars. D) They were produced inside dense interstellar gas. E) all of the above

3) Why did the solar nebula heat up as it collapsed? A) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula. B) As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy. C) Radiation from other nearby stars that had formed earlier heated the nebula. D) The shock wave from a nearby supernova heated the gas. E) Collisions among planetesimals generated friction and heat.

4) Why did the solar nebula flatten into a disk? A) The interstellar cloud from which the solar nebula formed was originally somewhat flat. B) The force of gravity from the Sun pulled the material downward into a flat disk. C) As the nebula cooled, the gas and dust settled onto a disk. D) It flattened as a natural consequence of collisions between particles in the spinning nebula, changing random motions into more orderly ones. E) The force of gravity from the planets pulled the material downward into a flat disk.

5) What happened during the accretion phase of the early solar system? A) Atoms and molecules in the gas bonded together and solidified. B) Particles grew by colliding and sticking together. C) The solar nebula differentiated into metals inside of the frost line and ices beyond. D) Large planetesimals captured atmospheres from the solar nebula. E) Earth gained its oceans from icy planetesimal capture.

6) According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane? A) The original solar nebula happened to be disk-shaped by chance. B) Any planets that once orbited in the opposite direction or a different plane were ejected from the solar system. C) The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk. D) The Sun formed first, and as it grew in size it spread into a disk, rather like the way a ball of dough can be flattened into a pizza by spinning it. E) Luck explains it, as we would expect that most other solar systems would not have all their planets orbiting in such a pattern.

7) Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula? A) light gases (H, He), hydrogen compounds (H2O, CH4, NH3), rocks, metals B) hydrogen compounds (H2O, CH4, NH3), light gases (H, He), rocks, metals C) light gases (H, He), hydrogen compounds (H2O, CH4, NH3), metals, rocks D) hydrogen compounds (H2O, CH4, NH3), light gases (H, He), metals, rocks E) hydrogen compounds (H2O, CH4, NH3), rocks, metals, light gases (H, He)

8) What percentage of the solar nebula's mass consisted of hydrogen and helium gases? A) 0.5 percent B) 5 percent C) 50 percent D) 98 percent E) 100 percent

9) What percentage of the solar nebula's mass consisted of rocky material? A) 0 percent B) 0.4 percent C) 2 percent D) 20 percent E) 80 percent

10) What kind of material in the solar nebula could remain solid at temperatures as high as 1,500 K, such as existed in the inner regions of the nebula? A) rocks B) metals C) silicon-based minerals D) hydrogen compounds E) molecules such as methane and ammonia

11) What was the frost line of the solar system? A) the distance from the Sun where temperatures were low enough for metals to condense, between the Sun and the present-day orbit of Mercury B) the distance from the Sun where temperatures were low enough for rocks to condense, between the present-day orbits of Mercury and Venus C) the distance from the Sun where temperatures were low enough for hydrogen compounds to condense into ices, between the present-day orbits of Mars and Jupiter D) the distance from the Sun where temperatures were low enough for asteroids to form, between the present-day orbits of Venus and Earth E) the distance from the Sun where temperatures were low enough for hydrogen and helium to condense, between the present-day orbits of Jupiter and Saturn

12) Why are the inner planets made of denser materials than the outer planets? A) The Sun's gravity pulled denser materials toward the inner part of the solar nebula, while lighter gases escaped more easily. B) Denser materials were heavier and sank to the center of the nebula. C) In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions. D) When the solar nebula formed a disk, materials naturally segregated into bands, and in our particular solar system the denser materials settled nearer the Sun while lighter materials are found in the outer part. E) In the beginning, when the protoplanetary disk was spinning faster, centrifugal forces flung the lighter materials toward the outer parts of the solar nebula.

13) Which of the following is the origin of almost all the large moons around the jovian planets? A) They are captured asteroids. B) They are captured comets. C) They are captured planets. D) They were formed by condensation and accretion in a disk of gas around the planet. E) They were formed by giant impacts.

14) What is the most likely reason that there are no giant planets beyond Neptune? A) Any planets forming beyond Neptune would have drifted out of the solar system due to the weakness of the Sun's gravity at this distance. B) There was no material to create planetesimals beyond the orbit of Neptune. C) By the time planetesimals grew to a large enough mass to hold onto an atmosphere, the solar nebula had been blown away. D) Any planet forming beyond Neptune's orbit would have been scattered outside of the solar system by gravitational encounters. E) There may be, but they would be so faint that astronomers have not found them yet.

15) Observations of young stars (as well as theory) tell us that when the Sun was young the solar wind A) was weaker than it is today. B) was stronger than it is today. C) was about the same strength as it is today. D) was nonexistent. E) blew outward only along the Sun's poles.

16) Which of the following has not been detected around other stars in the Galaxy? A) a collapsing nebula of gas B) flattened, spinning disks C) jovian planets D) terrestrial planets E) strong stellar winds

17) At first, the Sun's present-day rotation seems to contradict the prediction of the nebular theory because A) the theory predicts that the axis of rotation should not be perpendicular to the orbital plane of the planets, but it is. B) the axis of rotation precesses slowly, which the theory does not predict. C) the present-day rotation is in the opposite direction from that predicted by the theory. D) the theory predicts that the Sun should have been rotating fast when it formed, but the actual rotation is fairly slow. E) the theory predicts that the Sun should not have been rotating when it formed, but the Sun actually rotates today.

18) According to our theory of solar system formation, why does the Sun rotate slowly today? A) The Sun once rotated much faster, but it transferred angular momentum to charged particles caught in its magnetic field and then blew the particles away with its strong solar wind. B) The Sun once rotated much faster, but it transferred angular momentum to planets and other objects during close encounters. C) The Sun once rotated much faster, but it lost angular momentum due to internal friction. D) The Sun once rotated much faster, but it lost angular momentum because everything slows down with time. E) The Sun was born rotating slowly because the solar nebula had very little angular momentum.

19) Which of the following are relatively unchanged fragments from the early period of planet building in the solar system? A) the moons of Mars B) asteroids C) Kuiper belt comets D) Oort cloud comets E) all of the above

20) According to the nebular theory, what are asteroids and comets? A) They are the shattered remains of collisions between planets. B) They are the shattered remains of collisions between moons. C) They are leftover planetesimals that never accreted into planets. D) They are chunks of rock or ice that condensed long after the planets and moons had formed. E) They are chunks of rock or ice that were expelled from planets by volcanoes.

21) According to the nebular theory, how did the Kuiper belt form? A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula. B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet. C) It consists of objects that fragmented from the protosun during a catastrophic collision early in the formation of the solar system. D) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet. E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

22) According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets? A) Our theory is not quite correct because it cannot explain these exceptions. B) Most of the exceptions are the result of giant impacts. C) The exceptions probably represent objects that formed recently, rather than early in the history of the solar system. D) The exceptions probably represent objects that were captured by our solar system from interstellar space. E) The exceptions exist because, even though our theory is as correct as possible, nature never follows rules precisely.

23) Based on our current theory of Earth's formation, the water we drink comes from A) ice that condensed in the solar nebula in the region where Earth formed. B) chemical reactions that occurred in Earth's crust after Earth formed. C) chemical reactions that occurred in Earth's core after Earth formed. D) material left behind during the giant impact that formed the Moon. E) comets that impacted Earth.

24) The heavy bombardment phase of the solar system lasted A) several million years. B) several tens of millions of years. C) several hundreds of millions of years. D) about a billion years. E) to the present time.

25) Which of the following is not evidence supporting the giant impact theory for the formation of the Moon? A) Computer simulations show that the Moon could really have formed in this way. B) The composition of the Moon is similar to that of Earth's outer layers. C) The Moon is depleted of easily vaporized materials, as we would expect from the heat of an impact. D) Scientists have found several meteorites that appear to be the remains of the object that caused the giant impact. E) We see signatures of giant impacts on other planets.

26) Which of the following puzzles in the solar system cannot be explained by a giant impact event? A) the formation of the Moon B) the large metallic core of Mercury C) the backward rotation of Venus D) the extreme axis tilt of Uranus E) the orbit of Triton in the opposite direction to Neptune's rotation

27) The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict? A) Planets orbit around the Sun in nearly circular orbits in a flattened disk. B) the compositional differences between the terrestrial and jovian planets C) the equal number of terrestrial and jovian planets D) asteroids, Kuiper-belt comets, and the Oort cloud E) the craters on the Moon

28) The age of our solar system is approximately A) 10,000 years. B) 3.8 million years. C) 4.6 million years. D) 4.6 billion years. E) 14 billion years.

29) The age of the solar system can be established by radioactive dating of A) the oldest Earth rocks. B) the oldest rocks on the Moon. C) the oldest meteorites. D) the atmosphere of Mars. E) It hasn't been done yet, but the age of the solar system could be obtained from a sample of Io's surface.

30) What do meteorites reveal about the solar system? A) They reveal that meteorites are much older than the comets and planets. B) Nothing, because they come from other star systems. C) They reveal that the solar system once contained 10 planets. D) They reveal that the age of the solar system is approximately 4.6 billion years. E) They reveal that the early solar system consisted mostly of hydrogen and helium gas.

31) Suppose you find a rock that contains some potassium-40 (half-life of 1.3 billion years). You measure the amount and determine that there are 5 grams of potassium-40 in the rock. By measuring the amount of its decay product (argon-40) present in the rock, you realize that there must have been 40 grams of potassium-40 when the rock solidified. How old is the rock? A) 1.3 billion years B) 2.6 billion years C) 3.9 billion years D) 5.2 billion years E) none of the above

1) All the planets in the solar system rotate in the same direction as they orbit the Sun.

2) As viewed from above Earth's North Pole, all of the planets orbit the Sun in the same (counterclockwise) direction.

3) The more massive planets in the solar system tend to be less dense than the lower mass planets.

4) Within the frost line, planetesimals were composed entirely of rock and outside the frost line planetesimals were composed entirely of ice.

5) Impacts were extremely common in the young solar system but no longer occur today.

6) Earth's atmosphere resulted from the impact of icy planetesimals that originated in the outer regions of the Solar System.

7) The Moon probably formed at the same time that Earth formed, rather like the formation of a double planet.

8) Some radioactive isotopes found in meteorites suggest that the solar system may have been formed shortly after a supernova occurred nearby.

9) Based on our theory of how our own solar system formed, we would expect that other solar systems would be quite common.

10) Nebular theory predicts that other solar systems that formed in the same way should also have 8 planets.

11) Process of Science: We cannot test the nebular theory for the formation of the Solar System in a rigorous scientific way because the Sun and planets formed in the distant past.