Sirius A is classed as an Am star because the spectrum shows deep metallic absorption lines,[98] indicating an enhancement in elements heavier than helium, such as iron.[89][95] When compared to the Sun, the proportion of iron in the atmosphere of Sirius A relative to hydrogen is given by ,[14] which is equivalent to 100.5, meaning it has 316% of the proportion of iron in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of the entire star, rather the iron-peak and heavy metals are radiatively levitated towards the surface.[95]