47M-Galaxy Map

Astronomers have finished the largest high-resolution 3D map of the universe so far, after logging more than 47 million galaxies and quasars in a five-year survey. (newscenter.lbl.gov) The map comes from the Dark Energy Spectroscopic Instrument, or DESI, mounted on the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory in Arizona. DESI began its main survey in May 2021 and completed the originally planned map on April 15, 2026. (desi.lbl.gov) (physics.aps.org) A 3D galaxy map works by turning light into distance. DESI measures each object’s spectrum, then uses its redshift — the stretching of light as the universe expands — to estimate how far away that galaxy or quasar is. (physics.aps.org) (arxiv.org) DESI does that at industrial scale. Its 5,000 robotic positioners line up optical fibers with 5,000 targets at a time, and the instrument can collect redshifts for 5,000 objects roughly every 20 minutes. (physics.aps.org) (newscenter.lbl.gov) The project was supposed to gather data on 34 million galaxies and quasars over five years. It ended with more than 47 million galaxies and quasars, plus more than 20 million nearby stars for Milky Way studies. (newscenter.lbl.gov) (desi.lbl.gov) That extra reach matters because DESI is built to study dark energy, the unknown component that appears to be driving the universe’s accelerating expansion and makes up about 70% of the cosmos in the standard picture. By comparing how galaxies clustered billions of years ago with how they are arranged now, researchers trace how expansion changed over 11 billion years. (newscenter.lbl.gov) (desi.lbl.gov) The tension is that DESI’s earlier analyses, based on its first three years of data, pointed to a possibility that dark energy changes over time. That would conflict with the standard cosmology model, which treats dark energy as a fixed cosmological constant. (newscenter.lbl.gov) (physics.aps.org) Researchers have not settled that question yet. Berkeley Lab said the full five-year dataset will test whether the hint fades or strengthens, and APS Physics reported that the first cosmology analysis from the complete survey is expected in 2027. (newscenter.lbl.gov) (physics.aps.org) DESI has already released a major public dataset from its first 13 months, called Data Release 1, with high-confidence redshifts for 18.7 million objects, including 13.1 million galaxies and 1.6 million quasars. The collaboration says the survey will keep running through 2028 to widen the map and tighten tests of dark energy and dark matter. (arxiv.org) (newscenter.lbl.gov) For now, the headline result is a map: Earth at the center, tens of millions of points around it, and 11 billion years of cosmic history laid out in three dimensions. The argument over what that map says about dark energy comes next. (newscenter.lbl.gov) (physics.aps.org)