by: David Schlegel, DESI Project Scientist
July 22, 2021
Only eight weeks into DESI’s five-year mission, a 3-dimensional map of the universe is starting to take shape.
Plotted below is a “pie diagram” slice through the universe, with earth in the lower left, looking out in the directions of the constellations Virgo, Serpens and Hercules to distances beyond 5 billion light years. As this video progresses, the vantage point sweeps through 20 degrees towards Bootes and Corona Borealis. Each point represents a DESI target. The nearest are the bright galaxy sample (BGS as white points), then the luminous red galaxies (LRGs in red), emission line galaxies (ELGs in green), and finally quasi-stellar objects (QSOs in blue). Each of these targets is composed of 100 billion to 1 trillion stars, although we plot each target only as a single point. Gravity has clustered the galaxies into structures called the “cosmic web”, with dense clusters, filaments and voids.
DESI shuts down today for summer maintenance and upgrades, timed to coincide with the monsoon season in Arizona. When observations re-start in September, five times more galaxies will be observed at each sky location, gaps in this map will be filled in, and the area surveyed will eventually grow to span most of the sky visible from the northern hemisphere.