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Constellations

Constellations. Patterns in the Sky. Stars which are “close” to each other (in angle) form patterns called constellations. Not really close together Constellations change are unchanging year after year. Change over thousands of years is proper motion. Greek Myth.

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Constellations

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  1. Constellations

  2. Patterns in the Sky • Stars which are “close” to each other (in angle) form patterns called constellations. • Not really close together • Constellations change are unchanging year after year. • Change over thousands of years is proper motion

  3. Greek Myth • Constellations are named for characters in Greek mythology. • Asterisms are features within a constellation. • Orion’s belt

  4. Polaris - The North Star • Polaris is a star very near the north celestial pole. • About halfway up from the north horizon in DeKalb • Not visible south of the equator • Stars in the northern hemisphere rotate around Polaris each night. • Circumpolar stars don’t cross the horizon.

  5. Big Dipper Polaris • The Big Dipper is an asterism in the constellation of Ursa Major. • Two stars in the Dipper are pointer stars to Polaris. • End of bucket • Handle of Little Dipper • Circumpolar stars don’t cross the horizon. Big Dipper

  6. Seasonal Shifts • The Sun masks the light of the stars. • Constellations appear in certain seasons. • Stars peak overhead two hours earlier each month.

  7. Ecliptic • The earth is tilted 23º on its axis. • The celestial equator is not in line with the orbit of the sun, moon and planets. • The sun, moon and planets follow an imaginary curve called the ecliptic.

  8. Zodiac • The constellations that lie along the ecliptic are called the zodiac. • 12 constellations • The Sun passes through each one during the year.

  9. Stars are very numerous. Stars are “fixed” relative to each other. They produce their own light independent of the Sun’s location. They are very far away - the Greeks understood this. Planets are few in number (5 are visible to the unaided eye). Planets “wander” along the ecliptic relative to the stars. Their brightness does depend on the Sun’s location. Planets have complicated, but predictable orbits when viewed from the Earth. Stars and Planets

  10. Star Charts • Star charts are used to model the position of the stars. • Adjust for date and time • Websites can include planet positions, too. www.astronomy.com

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