Homework Assignment #5, Astronomy 115

Due Tuesday, November 28

Please do your homework on a separate page and do not turn in this homework assignment sheet. Also, Please staple multiple pages. Submission of homework assignments that are not your own work will result in a zero grade and disciplinary action.

    (Ch 15)

  1. What is located at the center of our galaxy & how far is the Earth from this location?

  2. Draw a picture of the Milky Way, and label the following features: disk, nucleus, globular clusters. Also include a scale bar so that someone can determine from your drawing the total size of the galaxy.

  3. Where in our Milky Way galaxy are the oldest stars found? What does this tell us about the formation of the galaxy?

  4. For years astronomers were unable to find the center of the Milky Way. Their observations were confused by dust that blocks the light of stars. What did Harlow Shapley observe to discover the true center of the Milky Way, and how did he measure distances?

    (Ch 16)

  5. List three types of galaxy. Which type of galaxy do you live in?

  6. How would you measure how much mass exists in a spiral galaxy?

  7. Explain why astronomers have deduced that galaxies contain a large quantity of "Dark Matter"

  8. Use Hubble's Law to determine the distance to a galaxy which is moving away at a velocity of 3,500 km/s. (Assume that H = 70 km/s/Mpc)

  9. How did humans first understand that the universe is expanding? What type of observations led to this conclusion?

  10. The Hubble Deep Field is a long-exposure image taken in 1995, which revealed thousands of galaxies, all found in one very small part of the sky. In 2004 a similar, even longer exposure was taken called the Ultra Deep Field. These images have been used to determine that there are at about 100 billion galaxies in the observable universe. Assuming that these galaxies are all roughly similar to the Milky Way, estimate the total number of stars in the known universe.