Astronomy 101 Final Exam Questions with Complete Solutions

Astronomy 101 Final Exam Questions with Complete Solutions The ancient Greeks identified 7 objects that change their location night-to-night relative to the background, "fixed" stars of the celestial sphere. They dubbed these objects the "wanderers". Which one of the "wanderers" wanders the most (i.e., changes its position the most from one night to the next) relative to the fixed stars of the celestial sphere? - CORRECT ANSWER The moon (has the fastest apparent motion in the sky, changing its location by about 12 degrees per day) Which ancient Greek thinker is known to have suggested that the Earth is moving around the Sun? - CORRECT ANSWER Aristarchus Which of the following is NOT an argument for showing that the earth must be round? - CORRECT ANSWER The sun is seen to be located within different constellations during the course of a year. Polaris is currently located very close to the North Celestial Pole. However, due to the effects of precession, we know that it has not always been located as close to the North Celestial Pole as it is today. Of the following, at which point in the past was Polaris located farthest from the North Celestial Pole? - CORRECT ANSWER The precessional period of the Earth's axis is 26,000 years. That means that the Earth's axis traces out a complete circle in the Celestial Sphere once every 26,000 years. If Polaris is close to the celestial pole now, that means it was also close 26,000 years ago, therefore exactly half (13,000 years) the amount of time ago it would have been furthest from its present location. In what fundamental way did the work of Galileo differ most from his ancient predecessors who had thought about the sky? - CORRECT ANSWER Galileo relied on instruments and experiments to reveal to him what Nature was doing, rather than on pure logic alone. Which of the following is a correct chronological sequence of famous thinkers, ordered from longest ago to most recent? - CORRECT ANSWER Aristotle, Ptolemy, Copernicus, Galileo. A hypothetical planet orbits the Sun exactly once every 8 years. Its mean orbital distance to the Sun must be equal to: - CORRECT ANSWER From Kepler's third law, we know that for a planet orbiting at an average distance of D from the sun with a period of revolution about the sun P: P2=D3 answer: 4 AU A single star in the process of forming starts by spinning slowly (while it is quite large and relatively cool). As the star collapses under the pull of its own gravity, its size decreases. As a result, its rate of spinning: - CORRECT ANSWER *conservation of angular momentum* answer: will increase The Moon is located about 60 Earth-radii away from the center of the Earth. If the moon were located 30 Earth-radii away from the center of the Earth, the gravitational force exerted on it by the Earth would - CORRECT ANSWER F= GM1M2/R2 answer: increase by a factor of four Suppose that, at aphelion, a planet's orbital speed around the Sun is 20 km/sec. Which one of the following could be the speed of that planet when it is at perihelion? - CORRECT ANSWER *since 20 km/s is when it's at aphelion and that is when it's at its slowest, answer must be faster than 20 km/s/* answer: 25 km/s According to Kepler's 2nd Law, comets (which have very eccentric orbits, carrying them far beyond the orbits of the planets) should spend the majority of their time: - CORRECT ANSWER Kepler's second law essentially tells us about the SPEED of planets in their orbits: When they are close to the Sun, the travel very quickly (and, therefore, spend little time there), whereas when they are far from the Sun they travel quite slowly (and, therefore, spend a lot of time in this portion of their orbit. answer: Far from the Sun. Consider the following four constituents of the Solar System: (1) Jupiter; (2) Sun; (3) Comets; (4) Moons and rings of planets. Which of the following represents the proper ordering, arranged from MOST massive to LEAST massive (when considering a class of objects like comets or moons and rings, this means the sum total of all of the comets or moons and rings combined): - CORRECT ANSWER Sun, Jupiter, Comets, moons and rings.