stellar population

In astronomy, classification of stars according to their chemical composition as determined by spectroscopy.

Population I stars have a relatively high abundance of elements heavier than hydrogen and helium, and are confined to the spiral arms and disc of the Galaxy. They are believed to be young stars formed from material that has already been enriched with elements created by nuclear fusion in earlier generations of stars. Examples include open clusters and supergiants. Population II stars have a low abundance of heavy elements and are found throughout the Galaxy but especially in the central bulge and outer halo. They are among the oldest objects in the Galaxy and include globular clusters. The Sun is a Population II star.