Category: 5. Stars from Adolescence to Old Age

The Sun and other stars cannot last forever. Eventually they will exhaust their nuclear fuel and cease to shine. But how do they change during their long lifetimes? And what do these changes mean for the future of Earth? We now turn from the birth of stars to the rest of their life stories. This…

Learning Objectives By the end of this section, you will be able to: The “life story” we have related so far applies to almost all stars: each starts as a contracting protostar, then lives most of its life as a stable main-sequence star, and eventually moves off the main sequence toward the red-giant region. As…

Learning Objectives By the end of this section, you will be able to: In the previous section, we indicated that that open clusters are younger than globular clusters, and associations are typically even younger. In this section, we will show how we determine the ages of these star clusters. The key observation is that the…

Star Clusters Learning Objectives By the end of this section, you will be able to: The preceding description of stellar evolution is based on calculations. However, no star completes its main-sequence lifetime or its evolution to a red giant quickly enough for us to observe these structural changes as they happen. Fortunately, nature has provided…

Learning Objectives By the end of this section, you will be able to: One of the best ways to get a “snapshot” of a group of stars is by plotting their properties on an H–R diagram. We have already used the H–R diagram to follow the evolution of protostars up to the time they reach the…