The Sun is part of a group known as population I stars, in which metals typically account for two to three percent of the star’s composition. Older stars – population II – have considerably less metals, ranging between 0.01% and 0.1%. A third, more elusive type of star dubbed population III are predicted to contain no metals whatsoever and be extremely massive. Due to their immense size, they would have burned out quickly when the Universe was still young and thus they have never been observed.