A small cross-section of the full DESI map showing millions of galaxies and quasars above and below our Milky Way’s galactic plane (Image Credit: Claire Lamman/DESI collaboration).
After over 5 years, astronomers using the DESI (Dark Energy Spectroscopic Instrument) have finally unveiled one of the most ambitious maps ever created, containing a massive three-dimensional reconstruction of the universe with more galaxies in it than any map ever previously made. Rather than just a traditional sky map that shows galaxies as flat points, this map was made to also capture depth, and to place the galaxies at their true distances across the span of billions of light-years.
Below is a short video exploring the full extent and mapping carried out over this 5-year project:
The map was made using data from millions of different galaxies and quasars (active galactic nucleuses), which were measured with spectroscopy to determine how much their light has been stretched because of the universe’s expansion. This stretching causes an effect known as redshift, where the light becomes redder as its wavelength is increased. Redshift allows scientists to calculate distance, which helps turn the sky into a layered, three-dimensional structure.
Out of this mapping emerges something known as the cosmic web: an intricate, weblike network of galaxy clusters, as well as voids and supervoids. Galaxies aren’t just scattered randomly — they actually trace large structures, known as filaments, which are shaped by gravity over billions of years. Studying these structures give astronomers very useful insight into how matter is distributed across our universe.
A photograph of the Pandora cluster of galaxies by the JWST, showing a flat view that contrasts the new three-dimensional mapping of DESI (Image Credit: NASA, ESA, CSA, Ivo Labbe (Swinburne), Rachel Bezanson (University of Pittsburgh); Image Processing: Alyssa Pagan (STScI)).
This map is about more than just structure. Not only does it exceed Hubble and Webb images like the one above in-depth perception, but it will also help solve one of the most elusive problems in physics: dark energy. When astronomers track how galaxies and their velocities are spread at different distances, scientists using DESI can measure the expansion rate of the universe at different points in space and time. This allows them to probe the nature of dark energy and potentially learn about the origins of this unknown force.
An animated GIF image showing cross-sections of the cosmic web at different depths, highlighting the extremely powerful mapping capabilities of this new instrument (Image Credit: D. Schlegel/Berkeley Lab using data from DESI) (Credit: D. Schlegel/Berkeley Lab using data from DESI)).
As DESI continues its survey of the sky, it will look at tens of millions of galaxies and continue to create a more complete and detailed map. With every new data release, we will be seeing more of the universe and gaining more insight into how it works on the largest scales imaginable.