1 A) 0 B) 1 C) 9 D) 100 billion 2 A) Venus, Earth, Jupiter B) Earth, Jupiter, Uranus C) Mercury, Mars, Saturn D) Mars, Jupiter, Neptune 3 A) Mercury, Earth, and Jupiter. B) Venus, Mars, and Saturn. C) Venus, Uranus, and Pluto. D) Neptune, Uranus, and Pluto. 4 A) Earth B) Jupiter C) Mars D) Venus 5 A) They all have solid surfaces for spacecraft to land on. B) They are composed mostly of hydrogen and helium. C) They all have rings. D) They are all far more massive than the Earth. 6 A) mass, surface area B) volume, mass C) mass, volume D) mass, radius 7 A) The Solar System B) The asteroid belt C) The ecliptic. D) The Oort Cloud. 8 A) 4.5 thousand years. B) 4.5 million years. C) 4.5 billion years. D) 4.5 trillion years. 9 A) The disk was the solar nebula and the bulge became Jupiter. B) A large belt containing asteroids in a gap between the orbits of Mars and Jupiter. C) The disk was the solar nebula and the bulge became the Sun. D) The formed the outer planets which eventually met up with the Sun. 10 A) All the planets orbit the Sun in the same direction. B) All the planets' orbits lie in nearly the same plane. C) The planets nearest the Sun contain only small amounts of substances that condense at low temperatures. D) All of the above. 11 A) the Sun's magnetic field attracted all the iron into the region around the Sun. B) the Sun's heat made it difficult for ices and gases to condense near it. C) the Sun's gravity sucked in iron and heavy material and the lighter materials floated farther away. D) the Sun is made mostly of iron, so the planets nearest it are formed of iron. 12 interior composition of Jupiter?A) Astronomers examined Jupiter's spectrum. B) Astronomers studied earthquake waves using instruments on Jupiter's surface. C) Astronomers calculated Jupiter's average density and compared it to those of abundant candidate materials, taking gravitational compression into account. D) All of the above. 13 A) Very small planets. B) Satellites of the giant planets. C) Planets that are found orbiting other stars. D) Large chunks of material (1 mm to several km in size) from which the planets were formed. 14 A) The moons probably formed from planetesimals orbiting the growing planets. B) Most of the moons likely were "captured" as they wandered too close to the planets. C) Many of the moons formed from material spewed out of volcanoes. D) Both b and c. 15 A) They can see the planet reflecting the star's light. B) They can be detected by the slight gravitational tug that they exert on their parent stars. C) They have bounced radar off of them. D) So far, no planets have been discovered around any other stars.
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