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Introduction to the Sky. Capella. Sirius. Aldebaran. Orion. Pleiades. Comet Hale-Bopp. Mars. Orion. “ Observation ” is not “ Looking ” Instead: . Study carefully Remember/record Try to make connections Identify systematic features. Motivations for Observing the Sky.
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Capella Sirius Aldebaran Orion Pleiades Comet Hale-Bopp
Mars Orion
“Observation” is not “Looking”Instead: • Study carefully • Remember/record • Try to make connections • Identify systematic features
Motivations for Observing the Sky • Curiosity • Practical applications • Navigation • Time-keeping • Calendar-keeping • Fear, religious belief • E.g. Astrology
Egyptian Pharoh Akhenaton and family communing with Sun God (ca. 1350 BC)
Astronomical Measurements Without Telescopes • Angles (quantitative) • Sky to Sky • Earth to Sky • Brightnesses (crude) • Colors, Shapes (crude) • Changes in above with time
Naked Eye Instruments for Angular Measures 1580 AD 150 BC
Naked Eye Instruments for Angular Measures Limiting accuracy ~ resolution of human eye ~ 1 minute of arc 1580 AD 150 BC
10 degrees 5 degrees Ursa Major (The Big Dipper)
"Hand-y" Angle Measuring (crude)
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
Mesopotamian carved stone, ca. 1000 BC showing Sun, Moon, Venus, and constellations
Greek amphora, ca. 400 BC, showing Leo, Aquila, Hercules, etc
Orion, Taurus, Lepus in a classical celestial atlas.
Pattern only traces the brighter stars in each region
More modern constellations Bode, 1801
Modern Constellations • "Official Constellations": 88 (est. 1930, IAU) • Boundaries of each well-defined • "Zodiac" = the 12 (13) constellations lying along the annual path of Sun through stars. (Names widely recognized but NOT all bright.)
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.
Contemporary "constellations"
Orion Projected View 3-D Distribution
Constellation Quiz • Two one-hour sessions offered M-R, 9 pm and 10 pm • Must reserve a place using on-line registration system • No special preparation needed • Bring a flashlight (red preferred), pencil, and clipboard (if you have one) • Cloudy or rainy weather will cancel the session • Check weather status after 6:30 pm at 924-7238
Capella Sirius Hyades Orion Pleiades Comet Hale-Bopp
Astrological Traits Associated With Planets