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Chapter Two

Chapter Two. Questions for the Day. What is a Constellation? What is Archeoastronomy? What are the motions of the sky?. What is a Constellation?. Constellations are apparent star patterns in the sky.

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Chapter Two

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  1. Chapter Two

  2. Questions for the Day • What is a Constellation? • What is Archeoastronomy? • What are the motions of the sky?

  3. What is a Constellation? • Constellations are apparent star patterns in the sky. • Constellation patterns were based in mythology, so each culture had their own set of constellations. • Constellation patterns are consistent set (88 in all) throughout the world. • Constellations are different from star clusters which are gravitationally bound set of stars.

  4. Constellation Simulator http://www.astro.wisc.edu/~dolan/constellations/java/Orion.html

  5. Constellation Mythology http://www.comfychair.org/~cmbell/myth/myth.html

  6. What is Archeoastronomy? • Archeoastronomy is the science of relating astronomical processes in the sky with objects located in archeological sites. • Objects on the site need to line up with astronomical events (equinoxes, solstices, eclipses, rising, and setting). • These archeological sites were usually used by astrologers, priests, tribal leaders.

  7. Stonehenge http://www.amherst.edu/~ermace/sth/photos.html

  8. Stonehenge – Before and After Phase I 2950-2900 BCE Phase III 2550-1600 BCE http://witcombe.sbc.edu/earthmysteries/EMStonehenge.html

  9. What are the Motions of the Sky? • Motions of Stars • Motion of the Sun • Motions of the Moon • Motions of the Planets

  10. Angular Distances • Degrees, Minutes, Seconds • 1° = 60’ • 1’ = 60” • Hours, Minutes, Seconds • 1 hour = 60 min = 15 • 1 min = 60 sec • Your hand equals 10 degrees in the sky.

  11. Angular Motion • The moon takes 27 days to orbit the Earth. What is its relative motion to the stars in ˚/day? In ˚/hour? v=d/t v=360°/27 days v=13.33 °/day v=13.33 °/day (1 day/ 24 hr) v=0.56 °/hour

  12. Motions of Stars • Diurnal • Due to the rotation of the Earth. • Annual • Due to the Earth orbiting the Sun. • Precession • Due to the wobble of the Earth on its axis. • All motions are represented in the SC001 chart.

  13. Diurnal Motion http://www.mhhe.com/physsci/astronomy/arny/instructor/ch01imagebank.html

  14. Annual Motion

  15. Motion of the Sun • The Sun travels along the ecliptic. • Due to the tilt of the Earth (23.5) • The Sun rises and sets at different positions each day. • The Sun’s annual motion is slightly faster than the rest of the stars. • The Sun moves 2 hours in Right Ascension each month, which is called Sidereal Time

  16. Motion of the Moon • The Moon has its own path around the sky due to a tilt of its revolutionary axis. • The Moon has phases due to amount of sun light reflecting off the moon. • The Moon’s synodic period (phase time) is longer (29.5 days) than its sidereal period (time of orbit, 27 days) • Eclipses occur when a line of nodes occur.

  17. Phases of the Moon http://www.astro.wisc.edu/~dolan/java/MoonPhase.html

  18. Line of Nodes http://www.ccs.neu.edu/home/sblanco/astro/moon.html

  19. Motions of the Planets. • The planets travel around the ecliptic. • The planets seem to go backwards in comparison the stars in some parts of their orbit because the Earth passes the planet in its orbit. This is known as retrograde motion. • The planet’s name means “wanderer” in both Greek.

  20. Planet’s Path

  21. Retrograde Motion

  22. Homework 2 • Look up on the web (at google.com or ask.com) to find information on an Archeoastronomy ( but not Stonehenge) site. Then write a paragraph summary about this site, please cite the website address. • The Earth takes 365.25 days to orbit the Sun. What is its relative speed to the stars in ˚/day? In ˚/hour? (Hint: Use the example in this PowerPoint.) • Page 34, CQ 4,10

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