1 The __________ of a planet is its apparent backwards movement as seen from Earth's sky.A) epicycle B) retrograde motion C) perihelion D) eccentricity 2 What is the Sun-centered model of our solar system called?A) epicentric B) geocentric C) heliocentric D) eccentric 3 Why is Venus the hottest planet, even though it isn't the closest to the Sun?A) its greenhouse effect B) its high albedo C) its high atmospheric pressure D) its surfuric acid rain 4 Mercury's extremely slow spin causes only __________ days to pass in __________ of Mercury's yearsA) three, two B) one, two hundred C) one hundred, one D) twenty-four, one 5 What characteristics do the gas giants have in common?A) ring systems and moons B) are very large, 1 - 300 times the mass of Earth C) composed of lightweight elements such as hydrogen and helium D) All of the answers are correct. 6 Where did Saturn's rings most likely come from?A) the formation of Saturn B) gravitational attraction of ringlets C) solar system formation D) leftover debris from moons that were destroyed 7 What is the composition of Saturn's atmosphere?A) hydrogen and helium B) hydrogen, helium, and ammonia ice C) sulfuric acid and hydrogen D) helium and oxygen 8 Neptune's atmosphere had a persistent storm called __________.A) the Giant Red Dot B) the Great Dark Spot C) the Spot D) the Big Cloud 9 Our solar system formed about 4.6 billion years ago whenA) a large planet broke into many pieces. B) a cloud of interstellar dust and gas began to condense. C) stars collided with one another. D) Jupiter formed as the largest planet. 10 Which of the inner planets has the highest average surface temperature?A) Mercury B) Venus C) Earth D) Mars 11 Nearly 5 billion years ago, a rotating mass of dust and gas gave rise to ____.A) the Sun and several other stars B) our solar system C) the Milky Way galaxy D) all solar systems 12 Scientists are convinced that other stars have planets in orbit about them. Without visiting these distant solar systems, how can they be sure?A) If our star has planets, then others must have them. B) There is evidence of a weak gravitational pull working on other stars. C) Other stars may have formed at the same time as the Sun. D) Space probes have returned photographs of these planets. 13 Planets sometimes seen to reverse direction in their course across the sky with respect to the distant stars. This effect, known as retrograde motion, is caused by ________A) Earth's revolution around the Sun B) the rotation of the Milky Way C) the elliptical orbits of the planets D) the distortion of starlight by the atmosphere 14 The bright celestial object that is often called both the morning star and the evening star is ________A) Jupiter B) the Andromeda galaxy C) a large comet D) Venus 15 Approximately how old is our solar system?A) 15 million years B) 250 million years C) 4.6 billion years D) 15 billion years