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Globular Star Cluster

General Information

1. Globular clusters are found in the galactic halo - above and below the plane of the Milky Way.

2. Most globular clusters move in highly eccentric elliptical orbits which take them far outside the Milky Way. They do not move with our galaxy’s disk rotation.

3. These clusters typically contain about 100,000 stars.

4. The clusters have kept their shape for 10 to 13 billion years and will continue to do so for another 15 to 20 billion years.

5. There are about 150-200 globular clusters associated with our galaxy.

6. Star clusters are important to astronomers because they use them to test their ideas of stellar evolution.

   a. They are able to do this because all the stars in the cluster are assumed to have formed at the same time.

   b. Theories of stellar evolution are based on computer models. The computer models are based on what we know about stars and the laws of physics. One of the things these models tell us is that different stars age at different rates.

   c. To test their theories, astronomers generate models of stars that would be found in a cluster. They then compare the appearance of this model cluster with observations of a real cluster. If there are significant differences, the astronomers change the model until it matches the real cluster.

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References

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