How has the cycle of star formation changed the chemical composition of the Milky Way Galaxy?

The cycle of star formation has fundamentally altered the chemical composition of the Milky Way Galaxy by enriching the interstellar medium with heavy elements over time.12

Originally, the Galaxy consisted primarily of hydrogen and helium, with very few heavier elements present. As stars evolve, they act as sites of nucleosynthesis, where high temperatures and pressures in their cores convert hydrogen into helium and subsequently fuse helium into heavier elements.231

These heavy elements are returned to the interstellar medium through processes such as supernova explosions and the ejection of material from planetary nebula shells or stellar winds. Because this enriched gas is then incorporated into new generations of stars, younger stars and current interstellar gas contain a higher concentration of heavy elements compared to the oldest stars in the Galaxy. This ongoing cycle ensures that the chemical makeup of the Galaxy is not static but gradually becomes more complex as successive generations of stars process and redistribute matter.1243