A new cosmic survey project known as the Dark Energy Spectroscopic Instrument (DESI) today released its first results: the most detailed 3D map of the universe to date, which shows the locations of 400,000 galaxies up to distances of 10 billion light-years. The map is the fruit of the project’s first 7 months of operation. Over the next 5 years the DESI team will log 35 million galaxies across one-third of the observable universe.
DESI’s aim is to understand dark energy, the mysterious force that seems to be accelerating the expansion of the universe. No one knows the origin of dark energy, but one key to understanding it would be finding out whether dark energy has been giving a constant push through the universe’s history or has varied as time passed.
DESI does this by accurately mapping galaxy positions through time. DESI—a high-tech detector attached to the veteran 4-meter Nicholas U. Mayall Telescope at Kitt Peak in Arizona—is looking for ripples in the distribution of galaxies known as baryon acoustic oscillations that were baked into the distribution of matter in the first few hundred years after the big bang. By measuring how far apart the ripples are at different stages in cosmic history, astronomers can see whether the universe’s acceleration has been constant or has changed over time.
In the map released today, each dot is an individual galaxy and each of those is made up of between 100 billion and 1 trillion stars. The map, shown above, reveals the view from Earth (lower left) for 5 billion light-years in the direction of the Virgo constellation and slowly shifting toward the constellation Boötes, which causes the apparent movement. The distribution of dots shows how gravity has pulled galaxies into clusters, filaments, and voids that make up the “cosmic web.” The early results were announced today in an online seminar organized by Lawrence Berkeley National Laboratory, which leads the DESI project, in place of sessions from the canceled American Astronomical Society annual meeting.
If DESI leads to a better understanding of dark matter, it could help cosmologists predict the eventual fate of the universe. Will it continue expanding forever, or be pulled into reverse, ending in a big crunch? Or will it rip itself apart?