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Astro 3 Final Study GuideSummaries 09/03/2008 16:51:00 Exam Multiple choice Exam: Thursday, March 20, 2008 3:00 PM - 6:00 PM MS 4000A E Chapter Review: Introduction Early observers grouped the stars visible to the naked eye into patterns called constellation which they imagined were attached to a vast celestial sphere centered on the Earth. Constellations have no physical significance, but are still used to label regions in the sky. Celestial coordinates are a more precise way of specifying a stars location on the celestial sphere. The nightly motion of the stars across the sky is a result of the Earths rotation on its axis. Because of the Earths revolution on its axis around the Sun, we see different stars at night at different times of the year. The Suns apparent yearly path around the celestial sphere (or the plane of Earths orbit around the Sun) is called the ecliptic . We experience seasons because Earths rotation axis in inclined to the ecliptic plane. At the summer solstice , the Sun is highest in the sky and the length of the day is greatest. At the winter solstice , the Sun is lowest and the day is shortest. Because of precession , the orientation of the Earths axis change slowly over the course of thousands of years. As the Moon orbits Earth, it keeps the same face permanently turned towards our planet. We see lunar phases as the fraction of the Moons sunlit face visible varies to us. A lunar eclipse occurs when the Moon enters Earths shadow. A solar eclipse occurs when the Moon passes between Earth and the Sun. An eclipse may be total if the body in question is completely obscured, or partial is only a portion of the surface is affected. If the Moon happens to be too far from the Earth for its disk to completely hide the Sun, an annular eclipse occurs. Because the Moons orbit around Earth is slightly inclined to the ecliptic, solar and lunar eclipses are relatively rare events. Astronomers use triangulation to measure the distance to planets and stars, forming the foundation of the cosmic distance scale , the family of distance-measurement techniques used to chart the universe. Parallax is the apparent motion of a foreground object relative to a distant background as the observers position changes. The larger the baseline the distance between the two observation pointsthe greater the parallax. The scientific method is a methodical approach employed by scientists to explore the universe around us in an objective manner. A is a methodical approach employed by scientists to explore the universe around us in an objective manner.... View Full Document

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