What is the difference between Population I, II, and III stars?

Population I, II, and III stars differ in their age, metallicity, and location in the galaxy.

Population I stars are young, metal-rich stars found in the disk of the Milky Way. They are typically less than 10 billion years old and have a high abundance of heavy elements, such as carbon, nitrogen, and oxygen. These stars are formed from gas and dust clouds that have been enriched by previous generations of stars.

Population II stars are older, metal-poor stars found in the halo and bulge of the Milky Way. They are typically more than 10 billion years old and have a low abundance of heavy elements. These stars are thought to have formed from the primordial gas that existed before the first generation of stars.

Population III stars are hypothetical, extremely metal-poor stars that are thought to have formed in the early universe. They are believed to have formed from the first clouds of hydrogen and helium that collapsed under their own gravity. These stars would have been massive and short-lived, and their remnants may be detectable as black holes or neutron stars.

Studying the properties of Population I, II, and III stars can provide insights into the formation and evolution of galaxies, as well as the early universe.