How would you expect a star that formed recently in the disk of the galaxy to differ from one that formed early in the history of the disk?

A star that formed recently in the disk of the galaxy is expected to have a higher fraction of elements heavier than hydrogen and helium, commonly referred to as "metallicity." This is because the interstellar medium in the galaxy becomes enriched with heavy elements through various processes over time, including the explosions of massive stars (supernovae) and the winds from dying stars. As new stars form from this enriched material, they inherit a greater abundance of these heavier elements.

In contrast, stars that formed early in the history of the galaxy originated from the primordial gas, which was predominantly composed of hydrogen and helium. At that time, very few heavy elements existed, as they had not yet been produced in significant quantities by stars.

Thus, the correct option highlights the evolutionary progression of star formation and the chemical enrichment of the galaxy's material, illustrating how younger stars are more metal-rich compared to their older counterparts. This understanding is crucial in studying stellar populations and the overall chemical evolution of galaxies.