The two GHOST spectra (labeled)

This mosaic shows the two GHOST spectra of HD 222925, a remarkably bright, chemically complex star. This star is a prime example of the type of object that GHOST will investigate. 

The dark lines in the rainbow are absorption lines — fingerprints of the gasses present in the star, including hydrogen, calcium, and also numerous metals like iron and gold. To the right a number of features from molecules in the Earth’s own atmosphere are seen. Any ground-based observation is subject to contamination from telluric (Earth-originating) sources like water vapor and oxygen. The effect of these lines is normally removed in subsequent steps of the analysis process.