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Introduction to the Night Sky and Constellations

Introduction to the Night Sky and Constellations. The Pleiades. M33. Milky Way. Zodiacal Light. Venus. M31 (Andromeda Galaxy). Light Pollution = Wasted Energy. Motivations for Observing the Sky. Curiosity Aesthetics Fear, religious belief. Discovery of: Patterns

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Introduction to the Night Sky and Constellations

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  1. Introduction to the Night Skyand Constellations

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

  3. Light Pollution = Wasted Energy

  4. Motivations for Observing the Sky • Curiosity • Aesthetics • Fear, religious belief Discovery of: Patterns Time Cycles

  5. Practical Applications of Astronomical Patterns & Time Cycles • 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. 10 degrees 5 degrees "Big Dipper" = Part of Ursa Major

  10. "Hand-y" Angle Measuring

  11. The Magnitude System = a ranking of brightness

  12. Example: Range of magnitudes in Big Dipper

  13. "Pan" of Little Dipper: a convenient magnitude template

  14. Star Colors (prism-dispersed image)

  15. "Celestial Sphere" Terminology

  16. Sky Wheel Orientation Meridian Zenith North Pole Horizon

  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

  18. 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

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

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

  21. Hevelius, Firmamentum 1690

  22. Hevelius, Firmamentum 1690

  23. Cellarius, Harmonia Macrocosmica, 1661

  24. More modern constellations Bode, 1801

  25. "Winter Triangle"

  26. "Official Constellations": 88 (est. 1930, IAU) • Boundaries of each well-defined • "Zodiac" = the 12 constellations lying along the annual path of Sun through stars. (Names widely recognized but not all bright.)

  27. Official boundaries of modern constellation Orion

  28. Significance of the Constellations? Not Much • Associations are arbitrary, man-made, culture-specific. • Not natural groupings: stars not necessarily close in 3D space. Shapes are specific to Earth's location in galaxy. • Constellations are transient because stars are all moving with respect to each other. • Used as convenient "address" for roughly locating objects in sky.

  29. Orion Projected View 3-D Distribution

  30. Constellation Quiz • Offered next two clear nights • Announced by email • Read Lab 1 in Manual • Work in groups to learn sky, then individual quiz with TA • Bring sky wheels, flashlights, handout • Orientation: "Starry Night" simulator next

  31. Supp, Ex, Alts

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