University of Michigan - Department of Astronomy




Version: Worksheet

Finding the Center of the Milky Way From Globular Clusters Worksheet

Part 1: Mapping clusters onto a star chart

You should have two star maps and list of clusters. The southern clusters have been mapped for you. Map the northern globular clusters (declination > 0°) from the table onto the northern star maps.

Part 2: Identify the clusters on the planetarium dome

  1. Your GSI assign two clusters from the list to each person. Record their ngc number, M number and/or names here:

  2. Circle your clusters on the star chart. Figure out how you will identify it on the planetarium sky.
  3. Your GSI will break you into 5 groups numbered 1 to 5. He/she will give a set of laser pointers to group 1.
  4. Group 1 will go first. Each group member simply has to point to his/her first cluster. When prompted by the GSI, move to the second cluster.
  5. If there is one constellation with more clusters than any other constellation, record its name and how many clusters are in it in table 1. Also record yes or no to whether or not that constellation lies in the fuzzy strip we call the Milky Way.
  6. When everyone has the first row of table 1 filled out, group 1 will hand the laser pointers to group 2, and the GSI will move the planetarium to the next position. group 2 will point out their clusters, and everyone will fill out the next row of the table.


Table 1: Constellations with the most clusters
Group No. Constellation Name Number of Clusters In Milky Way
  1. Based on table 1, what constellation is the center of the galaxy in? Explain your answer. Circle this constellation on your star chart(s).

  2. Is the constellation you identified in the previous question in the galactic disk? How can you tell?

Concluding Questions

  1. Look at the star maps. What constellation does the center appear to be in based on the star maps? How can you tell? Place an x on the star map at the location you think is the center.

  2. Is the center you get from looking at the star maps in the same constellation as the one you identified as the center of the galaxy in part 2? What are some reasons they might not be the same? Give at least 2 reasons.

  3. Determine the approximate RA and dec of center. Record the numbers and explain how you arrived at them.

  4. Can you ever see the galactic center and anti-center (the position opposite the center) at the same time from Ann Arbor? Explain.

Updated: 3/2/10 by SAM

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