Star Clusters, Page 69: [Previous Page] [Next Page] [Class Home Page] Textbook pages 392 - 401

Stellar Clusters on the H-R Diagram (Cont.)

Globular clusters are among the oldest objects in the galaxy. Globular Clusters are made up of hundreds of thousands of stars and are densely packed at their centers. Because these clusters are so old, the most massive stars in these clusters are less massive than our Sun! All stars more massive than this have run out of fuel and died long ago. If stars the mass of the Sun have died, what is the minimum AGE of this cluster? Below is a real H-R diagram for a globular cluster called M13. What is happening to the stars on the Main Sequence in this H-R Diagram?

What's happening at the center of stars lying in Red Giant Phase? Where are there stars about to go through a Helium flash? Where are there stars with Helium Fusion occurring at their cores? It should be clear from the examples above, with the use of an HR diagram, we can tell a lot about a clusters properties, like age. But most important, it gives us insight into the evolution of stars, something we'll never live long enough to see directly.