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Sky: Stars and Planets

Sky: Stars and Planets. http://www.cs.wright.edu/~tkprasad. Day and Night on Earth due to Sun. Moon Revolves Around the Earth. Moon rotates about its axis. Observe the constellations/planets moving anti-clockwise around the pole star as the night/day progresses. . Sky over : THE ENTIRE night.

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Sky: Stars and Planets

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  1. Sky: Stars and Planets http://www.cs.wright.edu/~tkprasad

  2. Day and Night on Earth due to Sun

  3. Moon Revolves Around the Earth

  4. Moon rotates about its axis

  5. Observe the constellations/planets moving anti-clockwise around the pole star as the night/day progresses. Sky over : THE ENTIRE night

  6. Beavercreek: April 18, 2009 : 8pm Pole Star

  7. Beavercreek: April 18, 2009 : 10pm Pole Star

  8. Beavercreek: April 19, 2009 : 12am Pole Star

  9. Beavercreek: April 19, 2009 : 3am Pole Star

  10. Beavercreek: April 19, 2009 : 6 am Pole Star

  11. Beavercreek: April 19, 2009 : 12 pm Pole Star

  12. Beavercreek: April 19, 2009 : 6 pm Pole Star

  13. Video of Star Trails Over a Night http://antwrp.gsfc.nasa.gov/apod/ap090413.html Hawaiian_Starlight_RotatingStarfield-APOD.flv

  14. Observe the constellations/planets moving anti-clockwise around the pole star and different constellations being visible towards the south. Sky over : A YEAR

  15. Beavercreek: Jan 22, 2009 : 10 pm

  16. Beavercreek: Mar 22, 2009 : 10 pm

  17. Beavercreek: Jun 22, 2009 : 10 pm

  18. Beavercreek: Sept 22, 2009 : 10 pm

  19. Beavercreek: Nov 22, 2009 : 10 pm

  20. Observe that the sky looks more or less the same on the same day of every year. Planet Jupiter moves clockwise through the constellations. Sky over : SAMe DAY OF THE YEAR

  21. Beavercreek: Nov 22, 2009 : 10 pm

  22. Beavercreek: Nov 22, 2010 : 10 pm

  23. Beavercreek: Nov 22, 2011 : 10 pm

  24. Beavercreek: Nov 22, 2012 : 10 pm

  25. Beavercreek: Nov 22, 2020 : 10 pm

  26. Beavercreek: Nov 22, 2022 : 10 pm

  27. Period of Planet’s Revolution In what follows, compare each slide with the preceding one

  28. Beavercreek: Nov 22, 2010 : 10 pm

  29. Beavercreek: Nov 22, 2022 : 10 pm Jupiter’s time of revolution around sun = 12 years

  30. Beavercreek: Oct 8, 2022 : 1 am Mar’s time of revolution around sun = 1.88 years = 22.56 months Time correction for 1.45 months (44 days) delay to get the “same” sky = 44 * 4 minutes

  31. Beavercreek: Oct 8, 2052 : 1 am Saturn’s time of revolution around sun = 30 years

  32. How fixed is pole star?

  33. Precession of Axis of Rotation and the Pole Star

  34. (cont’d) • Period of Wobble (for precession of equinoxes) = • Great/Platonic Year = • 25,770 yrs • Pole Stars: • Thuban (in Draco) 3000 BC • Polaris (Ursa Minor) 2100 AD • Vega (in Lyra) in 14,000 AD.

  35. Motivation for Ancient Astronomy • Predict and track terrestrial phenomena such as variations in the length of day, seasons, etc. by watching star patterns in sky. • Dictated agricultural decisions such as harvesting. • Observe that star patterns identified and named after animals and characters from Western Mythology in the Northern Hemisphere and material objects in the Southern Hemisphere. • More on Constellations later.

  36. Stars as Calendar • Constellations in the east rise a little earlier each evening, while constellations in the west set a little earlier. • People of ancient times used these seasonal changes in the star patterns in the sky as calendar to tell them when to plant and harvest crops. • For example, Leo and Virgo in the night sky would signify that the last frosts of the year have happened and it is safe to plant.

  37. Constellations of the Zodiac

  38. Constellations of the Zodiac

  39. Jan 1, 2009 Midnight

  40. May 1, 2009 Midnight

  41. Sept 1, 2009 Midnight

  42. Geocentric View (due to Ptolemy)

  43. Geocentric vs Heliocentric

  44. Planet Motion Visualized

  45. Motion of Mars against Background Stars

  46. Planets • Planets are distinguished from stars by their apparent “irregular”/ “wandering” motion through the constellations. • Planet means wanderer in Greek.

  47. Motion of Mars and Venus w.r.t Earth Geo-centric (Ptolemy [90-168AD]) vs Helio-centric Explanations (NicolausCopernicus (1473–1543) ) http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html http://www.mhhe.com/physsci/astronomy/applets/Retro/frame.html

  48. Audio http://www.youtube.com/watch?v=VsugmAEzf6U&feature=PlayList&p=C6319480C7FBB5E5&index=1 From: A Briefer History of Time (Hardcover) by Stephen Hawking, Leonard Mlodinow

  49. Seasons

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