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Introduction to the Night Sky and Constellations

Introduction to the Night Sky and Constellations

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Introduction to the Night Sky and Constellations

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  1. Introduction to the Night Skyand Constellations

  2. Auriga Orion Comet Hale-Bopp Taurus

  3. The Pleiades M33 Milky Way Zodiacal Light Venus M31 (Andromeda Galaxy)

  4. Motivations for Observing the Sky • Curiosity • Aesthetics • Fear, religious belief

  5. Discovery of Astronomical Patterns & Time Cycles  Practical Applications • Navigation • Time-keeping • Calendar-keeping Of immense value to all early cultures Could be critical survival technologies

  6. Astronomical Measurements Without Telescopes • Angles • Sky to Sky • Earth to Sky • (Brightnesses) • (Colors, Shapes) • Changes in above with time

  7. Units of Angular Measure

  8. Naked Eye Instruments for Angular Measures 1580 AD 150 BC

  9. The “Big” and “Little” Dippers

  10. 10 degrees 5 degrees "Big Dipper" = Part of Ursa Major

  11. "Hand-y" Angle Measuring

  12. The "Magnitude" System = a ranking of brightness

  13. Example: Range of magnitudes in Big Dipper

  14. "Pan" of Little Dipper: a convenient magnitude template: 2,3,4,5 mag

  15. Star Colors (prism-dispersed image)

  16. Main Actors in the Sky

  17. STARS Form background "reference frame" About 2000-5000 visible to naked eye over whole sky Patterns of bright stars seem "fixed", unchanging Move "in lockstep" from East to West and return to same position in sky after 23h56m Called the “diurnal motion”

  18. Positions of stars in night sky at given time change systematically during the year

  19. SUN Brightest object (by far!) Scattered sunlight masks stars during day Steady brightness Slow, eastward motion against stars, 1o per day Returns to same position after 365.25days, or one year.

  20. Lunar Phases MOON Second brightest object in sky (but much fainter than sun) Faster eastward motion against stars, 13o per day Dramatic change in (illuminated) shape or "phase" during cycle Cycle takes 29.5 days to return to same phase. 12 cycles per year Our "month" is based on lunar cycles

  21. Daily motions of Moon are easy to track

  22. Planets 5 brighter starlike objects that move with respect to the stars. Mercury, Venus, Mars, Jupiter, Saturn Merc, Venus always near Sun. Others, up to 180oaway. Motion is slower than Sun, Moon. Generally eastward, but loops to west

  23. "Retrograde Loop" in Mars Motion Eastward

  24. Other Easily Visible Phenomena } • Meteors • Comets • Star clusters • Diffuse nebulae • Milky Way • External galaxies Transient

  25. "Celestial Sphere" Terminology

  26. Sky Wheel Orientation Meridian Zenith North Pole Horizon

  27. Constellations • Constellations are the patterns formed by brighter stars on the sky • Patterns seem fixed (i.e. don't change over years) • Recognized for millenia, by all cultures • Associated with mythological figures, animals, instruments, etc

  28. Mesopotamian carved stone, ca. 1000 BC showing Sun, Moon, Venus, and constellations

  29. Greek amphora, ca. 400 BC, showing Leo, Aquila, Hercules, etc

  30. Orion, Taurus, Lepus in a classical celestial atlas.

  31. Pattern only traces brighter stars

  32. Hevelius, Firmamentum 1690

  33. Hevelius, Firmamentum 1690

  34. Hevelius, Firmamentum 1690

  35. Cellarius, Harmonia Macrocosmica, 1661

  36. More modern constellations Bode, 1801

  37. "Asterism"

  38. "Winter Triangle"

  39. "Winter Hexagon"