Final answer:
The abundance of heavy elements in a star tells us about its composition and age, with higher abundances indicating younger Population I stars and lower abundances indicating older Population II stars.
Step-by-step explanation:
The observed heavy element abundance in a star indicates its composition. Nearly all stars are composed mostly of hydrogen and helium, but they can differ significantly in their abundances of heavier elements. Population I stars, like the Sun, contain a higher percentage of these heavy elements, about 1-4% of their total mass. On the other hand, Population II stars, which are typically older and found in locations such as the outer galactic halo and globular clusters, have much lower concentrations of heavy elements, sometimes less than one-tenth of one percent when compared to Population I stars. This variation in metallicity can be linked to the ages of stars, with Population II stars generally being older than Population I stars. This is because heavy elements are produced by earlier generations of stars and disseminated through successive stellar life cycles, leading to their gradual buildup in later-generation stars.
Therefore, the presence of different levels of heavy elements, or metallicity, informs us about the evolution and age of stars. By examining the detailed star spectra and measuring metallicity, astronomers can trace the life cycles of stars from birth to demise. These observations contribute to our understanding of galactic evolution and the timeline of the universe.