supersolar

Supersolar is an astronomical adjective used to describe chemical abundances, typically metallicity, that exceed those of the Sun. It is a relative term applied to stars, H II regions, and galaxies to indicate higher heavy-element content than solar values. The most common quantitative measure is the iron-to-hydrogen ratio [Fe/H], defined as the base-10 logarithm of the ratio of a object’s iron to hydrogen abundance compared with the Sun. A star with [Fe/H] > 0 has supersolar iron abundance and, on the same scale, often a higher overall metallicity Z, though the relation between [Fe/H] and total metallicity depends on the detailed element abundance pattern and the solar reference used.

In the Milky Way, metallicity generally rises toward the Galactic center and in the bulge, where many stars and star-forming regions are supersolar, while the outer disk and halo tend to be subsolar. The Sun provides the standard solar reference point, so objects with near-solar values are described as solar-like rather than supersolar.

Supersolar abundances influence various astrophysical processes. In stellar evolution, higher metal content affects opacities, energy transport, and evolutionary tracks. In planet formation, greater metallicity is linked to higher probabilities of planet formation, particularly for gas giants. The term is scale-dependent and depends on the adopted solar abundance scale, which has varied across studies and over time. In descriptive usage, supersolar may refer to individual element abundances being higher than solar, or to overall metallicity exceeding the solar value.