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Unformatted text preview: ASTRONOMY 294Z: The History of the Universe Professor Barbara Ryden SOLUTIONS TO PROBLEM SET # 2 1) [20 points] With a telescope here on Earth, would we ever see Venus in a crescent phase? If so, sketch the relative positions of Venus, Sun, and Earth when that happens. To clarify the conditions under which a planet (or moon) appears as a crescent, I drew the above diagram. The planet is brightly illuminated on the hemisphere facing the Sun, and dark on the hemisphere away from the Sun. To see only the dark hemisphere (called the new phase), an observer must be along the dotted line labeled new. To see only the bright hemisphere (called the full phase), an observer must be along the dotted line labeled full. To see the planet half dark and half light, (called first quarter or last quarter), an observer must be along the dotted lines labeled quarter. To see the gibbous phase (mostly bright, with a little slice of dark), the observer must be in one of the two quadrants labeled GIBBOUS. Finally, to see the planet in its crescent phase (mostly dark, with a little slice of bright), the observer must be in one of the two quadrants labeled CRESCENT. To see a planet in its crescent phase, the observer must be farther from the Sun than the observed planet is. Since the Earth is farther from the Sun than Venus is, it is possible to see Venus in a crescent phase from the Earth. A diagram showing a configuration in which Venus would be a crescent is shown at the top of the next page. 2) [20 points]...
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This note was uploaded on 07/17/2008 for the course ASTRO 294 taught by Professor Ryden during the Winter '08 term at Ohio State.
- Winter '08