AST-1001 Lecture Notes - Lecture 2: Orbital Period, Celestial Coordinate System, Ecliptic

• School: App State
• Department: Astronomy
• Course: AST-1001
• Professor: Johnny Hollandsworth

Document Summary

2. 2 the celestial sphere (cont. : looking north, you will see stars seemingly circling counterclockwise around the celestial. They are not actually moving so much as we are. Earth"s rotation makes it seem like these stars are circling: some constellations around the celestial north pole never set (they never go below the horizon). We never stop seeing these constellations regardless of season, so the southern hemisphere never sees them. Conversely, there are constellations in the southern hemisphere that we never get to see here in the northern hemisphere. Earth"s axis of rotation is inclined (tilted) relative to the normal to its orbital plane by 23. 5 degrees which causes the seasons: some common misconceptions: seasons are caused by earth moving closer or further from the sun . Actually, in january the earth is about 1. 7% closer to the sun. The seasons arise because earth"s axis is not perpendicular to it"s orbit.