Astronomy CH2

Astronomy CH2 - 9/14/11 1 The Sky Our model of the...

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Unformatted text preview: 9/14/11 1 The Sky Our model of the universe: Our model of the universe: The earth is flat Our model of the universe: The earth is flat The sky is a bowl covering the earth This is really what we see! constellations Constellation = group of stars 9/14/11 2 Con stellation = group of stars together Con stella tion = group of stars stars Constellation = group of stars Asterism = small group of stars (example: Big Dipper) Big Dipper Big Dipper Polaris (North Star) 9/14/11 3 Little Dipper Big Dipper Polaris (North Star) Ancient constellations told stories... Ancient constellations told stories... Modern constellations are standardized Naming stars in a constellation Naming stars in a constellation Hipparchus of Rhodes Born 170 B.C.E Constructed the first star catalog, about 850 stars Invented the magnitude system Determined the length of the year (accurate to 6 minutes!) Discovered the precession of the equinoxes Developed the progenitor of trigonometry 9/14/11 4 Naming stars in a constellation Naming stars in a constellation = brightest Naming stars in a constellation = brightest = next brightest Naming stars in a constellation = brightest = next brightest Alphabetical (in Greek) in order of descending brightness. Naming stars in a constellation = brightest = next brightest Alphabetical (in Greek) in order of descending brightness. Stars may also have proper names (like Betelgeuse). The magnitude system Hipparchus divided stars into six classes, or magnitudes 1 st magnitude = brightest stars 2 nd magnitude = next brightest ... 6 th magnitude = dimmest visible Still used today! The original system has been extended: Objects brighter than stars (planets, moon,sun) Objects too dim do be seen with naked eye. 9/14/11 5 Apparent visual magnitude Magnitude is technically apparent visual magnitude: how bright the object appears to be from earth....
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Astronomy CH2 - 9/14/11 1 The Sky Our model of the...

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