AST101H1 Chapter 2: Constellations, the Seasons, the Moon - Chapter 2 (Sept 25th).docx
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AST101H1 Full Course Notes
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Chapter 2 discovering the universe for yourself. Constellation = a region of the stellar sky with well-defined borders; 88 official constellations (chosen in 1928 by members of the iau and named for familiar concepts in the western world) cover the celestial sphere. Every point in the sky belongs to some constellation or another. Celestial sphere = the imaginary sphere on which objects in the sky appear to reside when observed from earth. *for reference, we identify four special points and circles on the celestial sphere. North celestial pole = the point on the celestial sphere directly above earth"s north pole. South celestial pole = the point on the celestial sphere directly above earth"s south pole. Celestial equator = the extension of earth"s equator onto the celestial sphere. Ecliptic = the sun"s apparent annual path among the constellations. 23. 5 angle because that is the tilt of earth"s axis.