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Unformatted text preview: Astronomy 210 Spring 2011 Homework Set #2 Due in class: Friday, Feb. 4 Total Points: 50 1. [5 points] Suppose that in a heliocentric model, the stars were located on a true, literal celestial sphere in the form of a “shell” at a radius r shell . Put the shell at r shell = 10 EarthSun distances. If two stars, located in the plane of Earth’s orbit, are observed to be an angle θ near = 2 ◦ apart when the Earth is closest to them, how far apart θ far will they appear when the Earth is on the side of its orbit farthest from them? Would the difference Δ θ = θ near θ far be observable to the naked eye? Comment on the implications for the heliocentric vs geocentric debate. Hint : You may use the small angle approximation for this calculation. 2. The Receding Moon. For reasons that will become apparent later in the course, the Moon is slowly moving away from the Earth. This has several implications; here we will look at the impact on solar eclipses. Some data first: the radius of the Earth is 6370 km; the radius of the moon is 1740 km; the radius of the sun is 6 . 96 × 10 8 m (careful with units!); the semimajor axis and eccentricity of the Moon’s orbit are 384,000 km and 0.055; the semimajor axis and eccentricity of the Earth’sof the Moon’s orbit are 384,000 km and 0....
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 Spring '08
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 Astronomy, 4.6 billion years, 29.5 days, 3.68 cm

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