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Chapter 1 Astronomy Today 7th Edition Chaisson/McMillan

Chapter 1 Astronomy Today 7th Edition Chaisson/McMillan. Grab your text book. Charting the Heavens Day 5. Position in the sky. Look at the white board, you are facing north 5 fists and you have the North star Hold out your left arm, the overhead becomes West

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Chapter 1 Astronomy Today 7th Edition Chaisson/McMillan

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  1. Chapter 1 Astronomy Today 7th Edition Chaisson/McMillan Grab your text book

  2. Charting the Heavens Day 5

  3. Position in the sky • Look at the white board, you are facing north • 5 fists and you have the North star • Hold out your left arm, the overhead becomes West • Hold out your right arm, the windows become East • Behind you the bookshelves become South

  4. Now think of the position paper Star A is entirely in the Northern sky Star B is mostly in the Southern sky, but falls below the horizon at #4 E and W are at points 1 and 3

  5. Local Co-ordinate System • Azimuth – starts with north a 0° and south is 180° • Zenith is 90° zenith

  6. White board:With a partner draw a lunar eclipse and a solar eclipse

  7. Motion of the Moon Eclipses occur when Earth, Moon, and Sun form a straight line

  8. Motion of the Moon • Lunar eclipse: • Earth is between Moon and Sun • Partial when only part of Moon is in shadow • Total when it all is in shadow

  9. Motion of the Moon • Solar eclipse: Moon is between Earth and Sun • Partial when only part of Sun is blocked • Total when it all is blocked • Annular when Moon is too far from Earth for total

  10. Motion of the Moon Eclipses don’t occur every month because Earth’s and Moon’s orbits are not in the same plane

  11. The Measurement of Distance Triangulation: Measure baseline and angles, can calculate distance

  12. The Measurement of Distance Parallax: Similar to triangulation, but look at apparent motion of object against distant background from two vantage points

  13. The Measurement of Distance Measuring Earth’sradius: Done by Eratosthenes about 2300 years ago; noticed that when Sun was directly overhead in one city, it was at an angle in another. Measuring that angle and the distance between the cities gives the radius.

  14. Measuring Distances with Geometry Converting baselines and parallaxes into distances

  15. Measuring Distances with Geometry Converting angular diameter and distance into size

  16. Summary • Astronomy: Study of the universe • Scientific method: Observation, theory, prediction, observation, … • Stars can be imagined to be on inside of celestial sphere; useful for describing location • Plane of Earth’s orbit around Sun is ecliptic; at 23.5° to celestial equator • Angle of Earth’s axis causes seasons • Moon shines by reflected light, has phases

  17. Summary (cont.) • Solar day ≠ sidereal day, due to Earth’s rotation around Sun • Synodic month ≠ sidereal month, also due to Earth’s rotation around Sun • Tropical year ≠ sidereal year, due to precession of Earth’s axis • Eclipses of Sun and Moon occur due to alignment; only occur occasionally as orbits are not in same plane • Distances can be measured through triangulation and parallax

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