THE PLANETS ------------- You visit a hot little planet that rotates on its axis in 2 hours, while it revolves closely around its sun every 25 hours. You construct for the inhabitants an excellent calendar with a leap year that occurs in one time every a) year. $b) 2 years. c) 12 years. d) 25 years. Order the following by increasing radius. I. Sun II. Jupiter's orbit around Sun III. Earth's orbit around Sun IV. Sun's orbit around the Galaxy a) III, II, I, IV b) I, II, III, IV $c) I, III, II, IV d) I, II, IV, III Mnemonic: My Very Educated Mother Just Showed Us Nine Planets. Which planet(s) can never be seen on the meridian at midnight? $a) Mercury $b) Venus c) Mars d) Jupiter e) Saturn (Note: Mark all possible correct answers) The surface of Venus is mostly low density rock, while the average density of Venus is similar to that of Earth. The interior of Venus is therefore a) rapidly rotating b) composed of low density material $c) denser than the average density of Earth d) invisible e) homogeneous How much more solar energy does Venus receive than the Earth, due to the fact that Venus is 0.72 times as far from the Sun? a) 0.72 times as much b) 1/0.72 = 1.4 times as much c) 0.72 (squared) = 0.52 times as much $d) (1/0.72) (squared) = 1.92 times as much e) 0.28 times as much. From Earth, Mercury is difficult to see mostly because it a) has low albedo b) is very dense c) is very small $d) always appears near the Sun Mercury's atmosphere is likely to be weak or non-existent because of its a) small mass b) slow rotation c) high surface temperature d) high density $e) (a) and (c) Volcanos on Mars have become much larger than on Earth mostly because Mars lacks a) a thick atmosphere b) flowing water $c) plate tectonics d) a large moon Satellites of Mars probably formed a) out of a merger of telecommunications giants b) out of the same material from which Mars formed $c) in the asteroid belt, and were later captured d) in the Oort Cloud e) as a result of cometary bombardment Synchrotron radiation is produced $a) by electrons moving rapidly in a magnetic field b) by electrons traveling with a velocity determined by the temperature of the gas in which they are found c) by a "blackbody" d) by microwave ovens The atmosphere of Jupiter has few heavy elements due to a) evaporation b) the lack of heavy elements in the outer solar system c) the vacuum-like power of the Great Red Spot $d) gravitational settling toward the planet's center Jupiter's chemical composition is closest to that of a) Earth $b) the Sun c) Mars d) the Moon e) Venus The shape of Jupiter's magnetic field is flattened because of the solar wind and the a) low temperatues in the outer solar system a) planet's strong gravity $c) planet's rotation d) many moons Io's volcanic activity is driven mostly by heat from a) radioactivity $b) the Jupiter-Io tidal force c) Jupiter's magnetic fields d) the solar wind Synchrotron radiation from Saturn implies that the planet has a) powerful electrical storms b) an unseen companion $c) a magnetic field d) excess thermal radiation The sizes of particles comprising Saturn's rings are studied by analyzing a) shadows cast by the rings. $b) how light is scattered by the ring particles. c) excess radiation emitted by the rings. d) excess radiation emitted by the planet that is blocked by the rings. Uranus is peculiar because its a) radius is so large b) orbit is highly eccentric c) orbit is strongly inclined to the ecliptic plane $d) axis of rotation is in the ecliptic plane Seasons on Uranus are a) as long as Uranus' year b) non-existent $d) one fourth of Uranus' year, or about 20 Earth years long e) four times Uranus' year, or about 320 Earth years long Uranus is surrounded by a cloud of a) asteroids $b) hydrogen c) helium d) water molecules Which of the following is correct? a) the rotation axes of planets are perpendicular to their orbital plane (the ecliptic) $b) no planet's orbital inclination is more than 20 degrees from the ecliptic c) planets orbits are circular d) planets always rotate and revolve in the same direction Which of following are correct? $a) The Earth is closest to the Sun in January. b) The Earth is farthest from the Sun in January. c) The Earth is always at the same distance from the Sun. d) It's cold in winter because the Earth is farther from the Sun. Which of the following are correct? a) Mars is essentially in the same orbit as the Earth. b) There are canals filled with liquid water on Mars. c) If there is water, that means there is oxygen and therefore that we can breathe on Mars. d) All of the above. $e) None of the above. The terrestrial (inner) planets are characterized by (more than one answer may apply) a) low density b) rapid rotation c) large size $d) rocky composition Which of the following characterizes Jovian planets? (more than one answer may apply) a) high density b) slow rotation c) small size $d) mostly hydrogen and helium The Jovian planets have retained most of their atmospheres because a) they are further from the Sun's gravitational pull than the terrestrial planets. b) they are very warm and massive $c) they are very cold and massive d) the planet's rings "fence in" the planetary atmosphere What is responsible for heating the terrestrial planets from inside? a) temperature b) solar radiation $c) radioactivity d) fusion A planet can never be seen at opposition whose orbit relative to the Earth's has a $a) smaller radius b) larger radius c) longer year d) greater ellipticity The synodic period of a planet is the time during which a body in the solar system makes one orbit of the Sun relative to the Earth, i.e., returns to the same elongation. For a superior planet to the Earth, as the synodic period increases, its sidereal period must a) increase $b) decrease c) stay the same Consider the planets closer to the Sun than Jupiter. Of these planets, the two with the largest elongations have the ______ distances from the Sun. $a) largest b) smallest c) the same d) Not enough information. If Venus is observed to have a crescent phase while its elongation angle (away from the Sun) is 20 degrees, it must be ________ to/from the Earth than the Sun is. $a) closer b) farther c) equally distant d) can't tell from the information given. Venus is unusual because of its retrograde rotation. This means that Venus a) rotates much more slowly than the other planets b) does not always rotate with its axis at the same angle to the plane of the ecliptic $c) rotates in an opposite direction compared to most other planets in the solar system d) changes its direction of rotation The retrograde loops of Saturn are smaller than those of Jupiter because a) Saturn moves more slowly in its orbit $b) Saturn is farther away, and loop size is largely determined by the planet's parallax c) the motions of Saturn are more gradual since it has a lower temperature d) the older parts of the solar system move in smaller circular motions Why do Mercury and the Moon have almost no atmosphere? $a) The gravity at their surfaces is low, so most gas molecules travel fast enough to escape the planet. b) The temperature at their surfaces is high, so most gas molecules travel fast enough to escape the planet. c) The only gas molecules that they had originally were low in mass, so that they were immediately able to escape. d) They are both highly reflective. What might Mars have had it had a mass closer to those of Earth and Venus? a) an active interior. b) a larger atmosphere than Earth. c) abundant water, but larger ice caps. d) a magnetic field. $e) all of the above Which of the following assumptions of the original solar nebula hypothesis is probably wrong, in light of the evidence provided by extrasolar planets so far? a) Planets as massive as the Jovian planets must be composed primarily of hydrogen and helium. b) Jovian planets are likely to form relatively far from the star. $c) Planetary orbits do not shrink after the planet forms. d) Centrifugal forces (due to increasing orbital speeds) prevent the gas in the solar nebula from being pulled into the star. For a superior planet in our solar system, the correct sequence of events as seen from Earth is a) opposition, eastern quadrature, western quadrature, conjunction. b) opposition, western quadrature, conjunction, eastern quadrature. $c) opposition, eastern quadrature, conjunction, western quadrature d) conjunction, eastern quadrature, western quadrature, opposition. For an inferior planet in our solar system, the correct sequence of events as seen from Earth is $a) superior conjunction, greatest eastern elongation, inferior conjunction, greatest western elongation. b) inferior conjunction, greatest eastern elongation, inferior conjunction, greatest western elongation. c) superior conjunction, greatest western elongation, inferior conjunction, greatest eastern elongation. d) inferior conjunction, greatest eastern elongation, opposition, greatest western elongation. As seen from Earth, a superior planet can never be observed at a) superior conjunction. b) quadrature. $c) inferior conjunction. d) opposition. e) none of these. When at greatest western elongation, Venus may be observed $a) west of the Sun in the morning sky. b) west of the Sun in the evening sky. c) east of the Sun in the morning sky. d) east of the Sun in the evening sky. When at greatest eastern elongation, Venus may be observed a) west of the Sun in the morning sky. b) west of the Sun in the evening sky. c) east of the Sun in the morning sky. $d) east of the Sun in the evening sky. The greatest elongation of Mercury is a) about 45 degrees. b) about 90 degrees. $c) about 28 degrees. d) about 23.5 degrees. When Jupiter is at quadrature, the angle between Jupiter and the Sun as seen from Earth is a) 0 degrees. $b) 90 degrees. c) 180 degrees. d) 45 degrees. When Saturn is at conjunction, the angle between Saturn and the Earth as seen from the Sun is a) 0 degrees. b) 90 degrees. $c) 180 degrees. d) 45 degrees. When Mercury is at greatest elongation, the angle between Earth and the Sun as seen from Mercury is a) 0 degrees. $b) 90 degrees. c) 180 degrees. d) 45 degrees. Mars is a) observed at opposition every year. b) observed at opposition twice a year. $c) observed at opposition every two years. d) never observed at opposition.