How do Population I stars differ from Population II stars in terms of their metallicity?

Population I stars are characterized by their higher metallicity compared to Population II stars. Metallic content in stars refers to elements heavier than hydrogen and helium, which astronomers often refer to as "metals." Population I stars typically form in regions with a significant amount of gas and dust that have been enriched with heavy elements from previous generations of stars. This additional metallicity affects many properties of the stars, including their color, temperature, and brightness.

In contrast, Population II stars are generally older, found in the halos of galaxies, and formed early in the universe when the abundance of metals was much lower. As such, these stars exhibit low metallicity and are mostly composed of hydrogen and helium. The distinction in metallicity between the two populations is crucial for understanding stellar evolution and the chemical history of the universe.

The other options do not accurately reflect the defining characteristics of Population I stars in comparison to Population II stars, especially regarding their metallic content. Thus, recognizing that Population I stars are metal-rich is vital for distinguishing them in the context of stellar formation and evolution.