Quasars whose spectra show such broad absorption lines are known as "BAL quasars.
Previous studies had found a few examples of quasars whose broad absorption lines seemed to have disappeared between one observation and the next.
Diffuse Interstellar Bands (DIB) are broad absorption lines
in the spectra of stars indicating the existence of clouds of complex, unidentified molecules in the space between the stars.
The two pairs of broad absorption lines
indicate gas moving toward us at 500 and 1,300 km per second.