Problem
Answer the following questions based on the Hertzsprung-Russell diagram below for a star cluster.
1. What is the mass and spectral class of the stars that are just leaving the main sequence?
2. What happens in the stars' core region when the stars are just leaving the main sequence?
3. What is the end stage of the evolution of the stars that are just leaving the main sequence?
4. What is the age of this star cluster?