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Patterns in the sky -CONSTELLATIONS

Patterns in the sky -CONSTELLATIONS. Constellations are. Arbitrarily defined Culturally variable Specific to our region of space. Daily (diurnal) motion. How did we learn the Earth spins?. Unfolding distances and sizes of Sun, planets Foucault pendulum Coriolis forces.

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Patterns in the sky -CONSTELLATIONS

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  1. Patterns in the sky -CONSTELLATIONS

  2. Constellations are • Arbitrarily defined • Culturally variable • Specific to our region of space

  3. Daily (diurnal) motion

  4. How did we learn the Earth spins? • Unfolding distances and sizes of Sun, planets • Foucault pendulum • Coriolis forces

  5. A model of the sky – the CELESTIAL SPHERE

  6. North Celestial Pole Celestial equator South Celestial Pole

  7. North Celestial Pole Declination Celestial equator Right ascension South Celestial Pole

  8. North Celestial Pole DON’T GET THIS STUCK IN YOUR HEAD! Declination THE SPHERE DOES NOT REALLY EXIST! Celestial equator Right ascension South Celestial Pole

  9. Motion of the SUN

  10. Motion of the SUN • Eastward against distant stars by about 1 degree/day (reflection of our orbital motion)

  11. Motion of the SUN • Eastward against distant stars by about 1 degree/day • North and south with the seasons

  12. Motion of the SUN • Eastward against distant stars by about 1 degree/day • North and south with the seasons. This makes the Sun rise earlier, set later and stand higher in summer in each hemisphere.

  13. Motion of the SUN • Eastward against distant stars by about 1 degree/day • North and south with the seasons. This makes the Sun rise earlier, set later and stand higher in summer in each hemisphere. • IMPORTANT: seasons have to do with the angle between Earth’s orbit and axis, not with our changing distance from the Sun

  14. The MOON – orbit and phases

  15. Days since new: 10 9 8 7 6 5 4 3 19 18 14 12 11 movement 24 23 22 20

  16. SUNLIGHT Not to scale

  17. SUNLIGHT Not to scale

  18. SUNLIGHT Earth’s shadow is always here Cannot cause the cycle of phases Not to scale

  19. PLANETS – celestial wanderers • Mercury, Venus, Mars, Jupiter, Saturn • Sun, Moon were once grouped in • Move in complex patterns against “fixed stars” • Almost always near the ecliptic band (constellations of the Zodiac, like Sun and Moon)

  20. Mars, Jupiter, Pleiades star cluster March 8,9,10, 1989

  21. Retrograde (westward) motgion Example: Mars, late 2007

  22. Motions of the Earth • Daily rotation on its axis • Annual revolution (orbital motion) around Sun • Precession of the axis’ direction • Barycentric motion within Earth/Moon system • Sun’s orbit through the Galaxy

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