DESI Uses Distant Quasars to Map the Cosmic Web

An artist's impression showing how the Dark Energy Spectroscopic Instrument (DESI) uses distant quasars to map the large-scale structure of the Universe. As the quasars’ light travels across the cosmos it gets absorbed by intergalactic clouds of gas. This absorption can be detected in the light collected by DESI, allowing astronomers to map the pockets of dense matter. DESI is mounted on the U.S. National Science Foundation Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, a Program of NSF NOIRLab.