Ch 15: the Milky Way Galaxy Reading Questions

Ch 15: The Milky Way Galaxy Reading Questions

AstronomyName:Date:

15-1: Discovery of the Galaxy

1. Why did Thomas Wright call the Milky Way the “universe”?

2. How did Sir William Herschel and his sister Caroline contribute to our understanding of the Milky Way?

3. How did Harlow Shapley’s observations of star clusters contribute to our understanding of the Milky Way (this isn’t a one-sentence answer! Check out how much space I’m leaving you!)

15-2: Structure of the Galaxy

1. Astronomers commonly give the diameter of the galaxy as ______light years with the sun located about ______of the way from the center to the edge.

2. Describe the disk of the Milky Way, including what types of stars live there and overall properties

3. Describe the central bulge of the Milky Way, including the types of stars that are there and overall properties.

4. What are the two components of our galaxy and what are they made of?

5. Humans don’t live long enough to see stars move significantly along their orbits around the galaxy, but astronomers can observe the radial ______, proper ______, and ______of stars then calculate the ______and ______of their orbits. The results reveal the ______of the galaxy.

The mass of the galaxy is:

6. Draw a quick sketch of the difference between how disk stars and halo stars move.

15-3: Spiral Arms and Star Formation

1. List three things present in the spiral arms of the Milky Way.

2. What are “spiral tracers”, what types of stars make good spiral tracers and why?

3. O and B stars are common in the spiral arms. “Because they don’t live long enough to move away from the spiral arms, they must have ______.”

4. Studies of other galaxies show that their spiral arms are also marked by ______and other tracers like the ones in the Milky Way. Obviously ______are associated with ______.

5. Describe the two ways in which the spiral pattern of the Milky Way is slightly irregular.

6. Explain thoroughly the density wave theory of our galaxy.

7. The sun formed ______billion years ago as part of an association in a ______region, escaped from that association, and has circled the galaxy ______, passing through many spiral arms.

8. The spiral density wave theory has two problems, explain them.

9. Explain self-sustaining star formation.

15-4: The Nucleus of the Galaxy

1. If a ______photons of light left the center of the galaxy on a journey to Earth, only ______of those photons would make it through the dust.

2. List the possibilities of what might be at the center of our galaxy and why that is supported.

15-5: Origin and History of the Milky Way Galaxy

1. What are “metals”, according to astronomers?

2. How/where have metals formed over the course of the universe?

3. Compare and contrast Population I stars and Population II stars, including what they’re made of, where they are located, age, how they move, etc..

4. Describe galactic fountains (side note: Ms Rubio LOVES these!...you know, for what that’s worth)

5. Explain, using images, the Top-Down model (also known as the monolithic collapse hypothesis) for the formation of our galaxy.

6. Explain, using sketches, the Bottom-Up model for the formation of our galaxy.

7. Which model do you think is better? Explain.