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Unformatted text preview: Motions in the Sky What does the universe look like from Earth? Why do stars rise and set? How does the sky change with latitude and over the year? Apparent Motions - The Local Sky Read up to page 41 Zenith: The point directly overhead Horizon: All points 90 away from zenith Meridian: Line passing through zenith and connecting N and S points on horizon Altitude: Angle from the horizon Discussion: Motions in the Sky Orient yourself in the classroom, and visualize solar & stellar motions: Where's the north star? Which way do stars move around it? Where did the Sun rise today, and where will it set? Where is the Sun right now? Where is the Moon right now? Altitude of the celestial pole = your latitude Visibility of Stars Annual Motions - Actual
Actual motion = Earth orbits the Sun. Plane of orbit = ecliptic Lab topic Seasons Annual Motion: The sky varies as Earth orbits the Sun As the Earth orbits the Sun, the Sun appears to move eastward along the ecliptic. At midnight, the stars on our meridian are opposite the Sun in the sky. Lab topic Local vs. External Viewpoints Local vs. External Viewpoints Northern Hemisphere Southern Hemisphere How does the orientation of Earth's axis change with time?
Although the axis seems fixed on human time scales, it actually precesses over about 26,000 years. Polaris won't always be the North Star. Dates that Earth is opposite constellations has shifted by about a month over 2000 years Earth's axis precesses like the axis of a spinning top ...
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This note was uploaded on 11/09/2007 for the course ASTR 1010 taught by Professor Bagenal,fr during the Fall '07 term at Colorado.
- Fall '07