What is Stellar population?
[[File:Artist's impression of the Milky Way (updated - annotated).jpg|right|thumb|upright=1.4|Illustration of the Milky Way. The ''blue'' regions in the spiral arms are made of the younger population&nbsp;I stars. The ''yellow'' stars in the central bulge are the older population&nbsp;II stars. In reality, many population&nbsp;I stars are also mixed in with the older population&nbsp;II stars.]] [[Star]]s are grouped into '''stellar populations''', depending on the fractions of [[chemical element]]s inside the star. In astronomy, all elements except [[hydrogen]] and [[helium]] are called ''metals''. Elements like [[carbon]] and [[oxygen]] are called ''metals'' in astronomy, even though they are non-metals in chemistry. The ''[[metallicity]]'' of a star is the amount of ''metals'' in it. There are three stellar populations: '''population 1''', '''population 2''', and '''population 3'''. *Population 1 stars have high amounts of metals, like our [[Sun]]. They are mostly found in the spiral arms of the [[Milky Way Galaxy]]. They are the newest stars. *Population 2 stars have low amounts of metals. They are mostly found in the central bulge of the Milky Way Galaxy. They are older stars. *Population 3 stars have not been seen directly. They probably lived early in the [[Universe]]. They would have had almost no metals - they would be almost entirely hydrogen and helium. These stars probably created the first heavy elements that became part of later stars. == Related pages == *[[Cepheid variable]] [[Category:Stars]] {{science-stub}}