extreme Population I

In astronomy, "extreme Population I" refers to a specific category of stars and stellar assemblages that are very young and rich in heavy elements. These stars formed more recently than 10 billion years ago and include very hot, blue-white types like O and B stars, some of which are less than a million years old. Extreme Population I objects are found primarily in the arms of spiral galaxies, such as the Milky Way, and in young irregular galaxies. The Sun, at approximately 4.5 billion years old, is considered a Population I star. These stars are thought to have formed from interstellar gas that has been enriched by processes like supernova explosions, resulting in a chemical composition similar to that of the Sun, predominantly hydrogen and helium, with significant amounts of heavier elements like iron, nickel, and carbon.1