1. Describe four of the most common techniques used by astronomers to determine distances to stars and galaxies. Make sure you include the scientific theory behind each method and the range over which each method is considered valid. We need two different versions of posts. Please include work cited(direct quote needs quotation marks). Arround 200 words for each
2.
1. What is the cause of 21 cm radiation and how is it used by astronomers?
2. There is an organizational structure to the universe that exists at a level higher than that of the galaxy. Describe this structure?
3. When galaxies merge (collide) do stars actually collide? What is the likely outcome?
4. How do we know that quasars are not just nearby stars?
5. Just like stars provide the physical force to structure solar systems, black holes provide the physical force to structure galaxies. Is this statement true? Why or why not?