Friday, October 19, 2012
Stellar populations are groups of stars classified by astronomers according to their metal content or metallicity. So, the first stars that appeared in the universe, having a low metal content, are categorized as Population III; they are pair-instability supernovae that have exhausted much of their energy. Population II are second generation of stars which also arose early in the history of a galaxy from hydrogen and helium; red giants belong to this group. The newest stars in a galaxy belong to Population I and they formed from the debris of exploding Population II stars.