Astronomy Lecture Day 02 Scale, Ratios and Proportions

  1. Intro
  2. Collect Extra-credit HW
  3. Problems or questions
  4. Today’s goals
  5. Introduce the structures on the Universe
  6. Review ratios and proportions to better understand the scale of the Universe
  7. See the First exam study guide
  8. Structures of the Universe
  9. List the principle structures in increasing size
  10. Moons and Planets
  11. Stars: The Sun and star fields ( , )
  12. Planetary Systems
  13. Star clusters: an open cluster and a globular cluster

Galaxies: The Whirlpool galaxy

  1. Galaxy Clusters: rich cluster and poor clusters
  1. Scale Video: Astronomy Picture of the day on 20 Jan 2010: (6 min)
  2. Bookmark or favorite this web site, check it daily
  3. Another scale exercise: APOD 12 Mar 2012
  1. Working with ratios to better understand the scale
  2. Distance to the Sun compared to the diameter of the Earth
  3. Distance to Sun is 1 AU = 1.51011 m = 1.5108 km
  4. How to convert from m to km: divide by 1,000 or reduce the exponent by 3
  5. How to convert from km to m: multiple by 1,000 or increase the exponent by 3
  6. The distance between the Sun and Earth (center to center) is equivalent to 12,000 Earth diameters. (Imagine if the Earth was $1!)
  7. Diameter of the Milky Way compared to the diameter of the Solar System
  8. Diameter of Milky Way is 100,000 ly = 100,000(9.461015m) = 9.461020 m =9.461017 km
  9. Diameter of the Solar System is about 80 AU = 80(1.51011 m) = 1201011 m = 120108 km
  10. The diameter of the Milky Way galaxy is equivalent to about 79 millionSolar System diameters. (Imagine if the Solar System diameter was $1!)
  11. Distance to Whirlpool Galaxy (M51 or NGC 5194) compared to the diameter of the Milky Way
  12. Distance to Whirlpool galaxy is about 23 million ly = 23,000,000 ly = 23106 ly =(23106)(9.461015 m) = 2.181023m =2.181020 km
  13. Diameter of the Milky Way is about 100,000ly =9.461017 km
  14. The Whirlpool galaxy is about 230Milky Way diameters away.
  15. Working with proportions to better understand scale
  16. If the Earth had a diameter of 1 foot, what would be the diameter of the Sun?
  17. General rule for scale problems solved with proportions:
  18. Actual #1 = Diameter of the Earth = 26,378 km
  19. Actual #2 = Diameter of the Sun = 2696,000 km
  20. Model #1 = 1 foot
  21. Model #2 = unknown model size of the Sun, x
  22. , cancel the 2’s, cross multiply and solve for x.
  23. If the Earth had a diameter of 1 foot, the Sun’s diameter would be about 36 yards. Image a football (1 foot length) on the 36 yard line of a football field.
  24. If the Earth had a diameter of 1 inch, what would be the distance to the stars in Orion’s Belt?
  25. Actual #1 = Diameter of the Earth = 26,378 km
  26. Actual #2 = Distance of stars in Orion’s Belt = 1340 ly = 1340  (9.461015 m) = 1.271019 m = 1.271016 km
  27. Model #1 = 1 inch
  28. Model #2 = unknown model distance to stars in Orion’s Belt, x
  29. , cross multiply and solve for x.
  30. If the Earth had a diameter of 1 inch, the most distance star in Orion’s Belt would be about 16 million miles away. (16 million miles is 17% of an AU!)
  1. If the Sun had a diameter of 1 cm, what would be the diameter of the Milky Way?
  2. Actual #1 = Diameter of the Sun = 2696,000 km
  3. Actual #2 = Diameter of Milky Way = 100,000 ly = 100,000  (9.461015 m) = 9.461019 m = 9.461016 km
  4. Model #1 = 1 cm (about ½ an inch)
  5. Model #2 = unknown model diameter of the Milky Way galaxy, x
  6. , cross multiply and solve for x.
  7. If the Sun had a diameter of 1 cm, the Milky Way would have a diameter of 680,000 km. (If the Sun where 1 cm in diameter, the Milky Way would be almost as big as the real Sun!!
  1. Summary
  2. Pale Blue Dot image from the Cassini Spacecraft orbiting Saturn: APOD 16 Oct 2006
  3. Handout the HW, due on Tuesday
  4. We begin Units 5, 6 & 7 next week. Please look these over.
  5. Look at Dr. Fred’s Five Rules for the Apparent Motion of the Stars on Hot Tips Week 2