Chapter 6: Mastering Astronomy

when we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except _________ a) water b) carbon dioxide c) ammonia d) methane

b) carbon dioxide

the planets in our solar system are thought to have come from a) clumps of rocky material that exist between stars b) the same cloud of gas and dust in which the sun formed c) the sun (they were flung out from the spinning sun) d) a cloud of gas in the orion nebula

b) the same cloud of gas and dust in which the sun formed.

if the solar nebula initially had no angular momentum, a) the planets would orbit farther away from the sun b) the planets would orbit closer to the sun c) there would not be any planets orbiting the sun

c) there would not be any planets orbiting the sun

according to modern scientific dating techniques, approximately how old is the solar system? a) 4.5 billion years b) 4.6 million years c) 10,000 years d) 14 billion years

a) 4.5 billion years

suppose you view the solar system from high above earth's north pole. which of the following statements about planetary orbits will be true? a) all the planets orbit counterclockwise around the sun b) all the planets except uranus orbit the sun counterclockwise; uranus orbits in the opposite direction c) the inner planets orbit the sun clockwise while the outer planets orbit the sun counterclockwise d) the inner planets orbit the sun counterclockwise while the outer planets orbit the sun clockwise

a) all the planets orbit counterclockwise around the sun

according to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? a) its mass, temperature, and density all increased b) it got hotter, its rate of rotation increased, and it flattened into a disk c) its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the jovian planets, and central temperatures rose to more than a trillion kelvin d) it gained energy, it gained angular momentum, and it flattened into a disk

b) it got hotter, its rate of rotation increased, and it flattened into a disk

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 _________ a) terrestrial planets sometimes form beyond the jovian planets b) ice-rich objects the size of terrestrial planets should exist in all solar systems c) this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula

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

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? a) the nebular theory holds that moons of any size should be rare, so finding 1 is not too surprising but finding 6 would be very surprising. b) the nebular theory says that only planets at least as large as earth can have large moons, and 6 earth-size planets would not be likely to form in one solar system c) unusually large moons form in giant impacts, which are relatively rare events

c) unusually large moons form in giant impacts, which are relatively rare events

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? a) you'll have 0.75 kilogram of the radioactive substance remaining b) you'll have 0.5 kilogram of the radioactive substance remaining c) you'll have 0.25 kilogram of the radioactive substance remaining d) all the material will have completely decayed

c) you'll have 0.25 kilogram of the radioactive substance remaining

as the solar nebula collapsed, it became a disk because a) the initial cloud was disk shaped b) the sun's gravity pulled the nebula material into the ecliptic plane c) the self-gravity of the nebula pulled the material into the ecliptic plane d) collisions between particles made the particles go in more-or-less the same direction

d) collisions between particles made the particles go in more-or-less the same direction

what do we mean by the frost line when we discuss the formation of planets in the solar nebula? a) it is the altitude in a planet's atmosphere at which snow can form. b) it is another way of stating the temperature at which water freezes into ice c) it marks the special distance from the sun at which hydrogen compounds become abundant; closer to the sun, there are no hydrogen compounds d) it is a circle at a particular distance from the sun, beyond which the temperature was low enough for ice to condense

d) it is a circle at a particular distance from the sun, beyond which the temperature was low enough for ice to condense

the jovian planets in our solar system are _________ a) mercury, venus, earth, and mars b) pluto and eris c) io, europa, ganymede, and callisto d) jupiter, saturn, uranus, and neptune

d) jupiter, saturn, uranus, and neptune

according to our theory of solar system formation, what are asteroids and comets? a) chunks of rock or ice that were expelled from planets by volcanoes b) chunks of rock or ice that condensed after the planets and moons finished forming c) the shattered remains of collisions between planets d) leftover planetesimals that never accreted into planets

d) leftover planetesimals that never accreted into planets

the terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. according to modern science, where did the elements heavier than hydrogen and helium come from? a) they were produced by gravity in the solar nebula as it collapsed b) they were made by chemical reactions in interstellar gas c) they have been present in the universe since its birth d) they were produced by stars that lived and died before our solar system was born

d) they were produced by stars that lived and died before our solar system was born

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 a) with a higher abundance of metals and larger size b) being made entirely of H/He gas c) the same as they are now d) with a higher abundance of hydrogen compounds and larger size

d) with a higher abundance of hydrogen compounds and larger size

the inner planets are small and rocky and the outer planets are mostly large and gaseous because a) 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 b) the spin of the disk caused the denser rock and metals to remain towards the center of the solar system, while the lighter material were flung farther from the sun c) the sun's gravity caused the denser rock and metals to settle towards the center of the solar system while the lighter materials remained farther from the sun d) hydrogen is more abundant than rocks and metals so that beyond the frost line hydrogen froze to form the jovian planets

a) 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

as the solar nebula collapsed under its own gravity, a) it heated up and spun up b) it cooled down and spun up c) it heated up and spun down d) it cooled down and spun down

a) it heated up and spun up

in essence, the nebular theory holds that _________ a) our solar system formed from the collapse of an interstellar cloud of gas and dust b) the planets each formed from the collapse of its own separate nebula c) nebulae are clouds of gas and dust in space d) the nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our sun and another star

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

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 a) been smaller in mass than the real Jupiter, but still made mostly of h/he b) turned out pretty much the same as the real jupiter c) been similar in composition to earth, with a much smaller mass than the real jupiter

c) been similar in composition to earth, with a much smaller mass than the real jupiter

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 __________ a) terrestrial planets should orbit in a different plane from the plane of the jovian planets b) all the planets formed in a rotating, disk-shaped nebula c) star systems should have equal numbers of terrestrial and jovian planets

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

which of the following types of material can condense into what we call ice at low temperatures? a) rock b) hydrogen compounds c) metal d) hydrogen and helium

b) hydrogen compounds

the temperature of the protoplanetary disk allowed a) hydrogen compounds, rocks, and metals to freeze in the inner region only b) rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds to freeze only in the outer region c) rocks and metals to freeze in the inner region only, and hydrogen compounds to freeze in the outer region only d) rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds and H/He gases to freeze only in the outer region

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

the planet in our solar system with the highest average surface temperature is _________ a) earth b) venus c) neptune d) mercury

b) venus

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 when two gigantic asteroids collided with one another c) the moon formed from material blasted out of earth's mantle and crust by the impact of a mars-size object d) the moon formed just like earth, from accretion in the solar nebula

c) the moon formed from material blasted out of earth's mantle and crust by the impact of a mars-size object