Diagram Age Release For Free

By placing the stars in a globular cluster on a Hertzprung-Russell diagram, astronomers can determine the cluster's age by looking at the main sequence turnoff point and comparing it with models of stellar evolution.

The open star clusters are relatively young, and most of their stars have not yet left the main sequence in the Hertzsprung-Russell, abbreviated H-R, diagram. The youngest clusters, such as the Pleiades, retain all but the topmost part of the main sequence.

Cluster HR Diagrams: Since all the stars in a cluster formed at the same time, they are all the same age. A very young cluster will have a HR diagram with a cluster of T-Tauri stars evolving towards the main sequence. As time passes the most massive stars at the top of the main sequence evolve into red giants.

In the image above, you can see a schematic HR diagram with plots of lines that represent the Main Sequence for a number of open clusters. From the location of the Main Sequence Turn-Off, you can see that NGC 2362 is the youngest, then h & ? Persei, and M67 is the oldest of the clusters.

Astronomers generally use the HR diagram to either summarise the evolution of stars, or to investigate the properties of a collection of stars.

By plotting the stars on the H-R diagram according to their temperatures, spectral classes, and luminosity, astronomers can classify stars into their different types. Today, there are different versions of the chart, depending on what specific characteristics astronomers want to chart.

Globular clusters ? which are round, symmetrical clusters containing hundreds of thousands to millions of stars ? were thought to be around 13 billion years old, nearly as old as the universe itself.