| Population I |
|
A collective name for stars and star clusters within the Galaxy that exhibit characteristics suggesting they are relatively young and are confined to the galactic plane, especially the spiral arms. The distinction between Population I and Population II was first made by W. Baade in 1944, who introduced the terms. Typical Population I objects are hotter main-sequence stars, open clusters, and associations. Interstellar material is also associated with Population I. The stars are relatively abundant in heavier elements because the material from which they formed had been enriched by the products of nucleosynthesis in earlier generations of stars. See also: astration. |