What indicates the abundance of a specific ion in stellar spectra?

The abundance of a specific ion in stellar spectra is indicated by the spectral line strength. When light from a star is analyzed, it reveals a spectrum that contains a series of lines, each corresponding to specific wavelengths absorbed or emitted by ions in the star's atmosphere. The strength of these spectral lines correlates directly with the amount of the specific ion present; stronger lines indicate a higher abundance of that ion, while weaker lines suggest a lower presence.

For instance, if an astronomer observes a particularly strong spectral line for hydrogen in a star's spectrum, they can infer that hydrogen is abundant in that star. This method is a fundamental aspect of spectroscopy, allowing astronomers to determine the composition of stars and other celestial bodies.

The star's luminosity, temperature, and distance do not directly reflect the abundance of specific ions, as they relate to different properties of the star itself rather than the spectral characteristics of the light emitted.