Jon Chase describes how different elements absorb and emit light of specific wavelengths or colours. He explains how this can be used to identify which elements are present in distant stars by analyzing the spectrum of radiation coming from these stars. Teacher notes: You could discuss how white light can be split into its spectrum and students could make their own CD spectrometer. Students could investigate the flame colours produced by different elements. A piece of metal could be heated to show how the colour changes with increasing temperature. Relate this to the colours of different stars.