This is because All stars in a single cluster have the same AGE and DISTANCE.
All these stars formed within the collapse of a molecular cloud,
at the same time, hence they are all the same age. To construct this diagram, we would obtain the
temperature and luminosity of each star in the cluster, and simultaneously plot each star on this
diagram.
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Cluster at Birth. Stars to the upper left of the diagram are MASSIVE stars. Stars toward the middle, have masses like our Sun. The small stars to the lower right have masses much less than our Sun. |