What is Metallicity?
Metallicity is a term used in astronomy to refer to the proportion of matter in a star made of elements other than hydrogen and helium. In astronomical parlance, such elements (lithium, carbon, oxygen) are called metals. The quantity of metals in a star depends on its size, age, and most importantly, how much of its light elements it has fused into heavy elements for nuclear fuel. For instance, the Sun, a main sequence star with an age of about 4.57 billion years, has a metallicity of approximately 1.6 percent by mass. As the Sun gets older, its metallicity will increase until it becomes a Red Giant star, burns the rest of its fuel, then sits there for the rest of eternity as a glowing husk called a white dwarf. Thanks to the magic of spectrometers, astronomers can analyze the chemical composition of faraway stars, even some stars in nearby galaxies. Metallicity is one of the primary variables that astronomers have used to classify various stars as white dwarfs, red giants, main sequen
