the spectra of quasars. In addition to the greatly redshifted emission lines already discussed, some quasars display mysterious absorption lines. These are not as redshifted as the emission lines, and their existence implies that some material between the quasar and Earth is capable of absorbing the quasar’s light. Yet for many quasars no such material has been discerned. Because the central galaxy in this image creates similar absorption lines, many scientists now believe that faint intervening galaxies are the cause of the anomalous absorption lines.