Quasar light reveals intervening gas through absorption lines
Light from distant quasars travels for billions of years and picks up narrow absorption lines from hydrogen and metals in galaxies and the intergalactic medium along the line of sight.
The Lyman-alpha forest of many thin lines maps how gas was distributed as the universe expanded and galaxies grew. Quasars thus backlight the cosmic web’s invisible threads.
A blinding engine becomes a flashlight for everything in front of it. Quasar spectra turn bright nuclei into probes of otherwise dark gas.
Comments
0 comments