1. What is the helium flash and what causes it? 2. Explain how and why the turnoff point on the H-R diagram of a cluster is related to the cluster’s age. 3. Why do astronomers believe that globular...

1. What is the helium flash and what causes it?

2. Explain how and why the turnoff point on the H-R diagram of a cluster is related to the cluster’s age.

3. Why do astronomers believe that globular clusters are made of old stars?

4. What are Cepheid variables, and how are they related to the instability strip?