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Consider the dome of the sky over our heads….

Consider the dome of the sky over our heads…. mixing bowl. Consider the dome of the sky over our heads…. inverted mixing bowl …. Celestial Sphere: Extension of the Earth ’ s Coordinates. celestial sphere N/S celestial poles celestial equator. Like a salad bowl over your head!.

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Consider the dome of the sky over our heads….

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  1. Consider the dome of the sky over our heads…. mixing bowl

  2. Consider the dome of the sky over our heads…. inverted mixing bowl ….

  3. Celestial Sphere: Extension of the Earth’s Coordinates • celestial sphere • N/S celestial poles • celestial equator Like a salad bowl over your head!

  4. The Zodiac throughout the Year Example: In Winter sun in Sagittarius, Gemini at night sky;in summer sun in Gemini, Sagittarius at night sky

  5. Zodiacal signs vs. Constellations • “Constellation” is a modern, well-defined term • - Some constellations are big, some are small on the celestial sphere • “Zodiacal sign” is the old way of dividing the year and the Sun’s path into 12 equal parts • zodiacal sign is exactly 30 degrees “long”

  6. The Ecliptic • The sun appears to move along a plane in the sky referred to as the ecliptic. • The other planets also appear to move close to the ecliptic.

  7. Sun Gemini Taurus Leo Cancer Aries  East West  South If you could see stars during the day, the drawing below shows what the sky would look like at noon on a given day. The Sun is near the stars of the constellation Gemini. Near which constellation would you have expect the Sun to be located at sunrise on this day? • Leo • Cancer • Gemini • Taurus • Aries 0/0

  8. Celestial Sphere Rotation  Path of Star B Celestial Sphere Path of Star A 4 North Star 2   3 North Star Earth’s Equator Horizon 6 PM  Celestial Sphere Rotation North At what time will Star B be located high in the Northwestern sky? • 4:00 am • 10:00 am • 2:00 pm • 7:00 pm • 1:00 am

  9. Celestial Sphere Rotation  Path of Star B Celestial Sphere 1 Path of Star A 4 North Star 2   3 North Star Earth’s Equator Horizon 6 PM Sphere Rotation  North If you were able to see the motion of star B be at Noon, over a period of 15 minutes what direction would it appear to move? • west (to the left) • east (to the right) • South (out of the page) • away from the horizon (up) • toward the horizon (down)

  10. Hipparchus • Lived about 150 BC • 850 Star Positions • Defined Magnitudes • Discovered Precession Cataloger of the Heavens

  11. Precession of the rotation axis

  12. Precession causes the north celestial pole to drift among the stars, completing a circle in 26,000 years.

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