As light from background quasars passes through the gas and dust in foreground galaxies and cosmic filaments, it carries information about speed, composition and temperature of the intervening space. (ibtimes.com)
The primordial infalling gas resides a mere 190,000 light - years from the galaxy — relatively nearby on galactic length - scales — and is revealed in silhouette in the absorption spectrum of the more distant background quasar QSO J1444535 +291905. (keckobservatory.org)
The galaxies were initially found by the absorption of background quasar light passing through the galaxies. (sciencedaily.com)