Final answer:
The abundance of heavy elements in a star is related to its age. Older stars have lower abundances of heavy elements.
Step-by-step explanation:
The abundance of heavy elements in a star is related to its age. Based on observation, the older a star is, the lower its abundance of heavy elements. In the Sun and other population I stars, the heavy elements account for 1-4% of the total stellar mass. On the other hand, population II stars in the outer galactic halo and in globular clusters have much lower abundances of heavy elements, often less than one-hundredth the concentrations found in population I stars.
This difference in heavy element abundances is due to the different generations of stars. Population II stars are older and formed when the universe was younger, so they had less time to accumulate heavy elements through stellar processes.