SDSS-V releases first all-hemisphere optical spectra, mapping 1.5 million stars and 500,000 black hole targets

The Sloan Digital Sky Survey V has published Data Release 20 (DR20), its largest spectroscopic catalog to date, containing over three million new spectra of stars, galaxies, and quasars. For the first time, the release incorporates optical spectra from the Southern Hemisphere, gathered with the du Pont 2.5-meter telescope at Las Campanas Observatory in Chile, alongside continued observations from the Sloan Foundation 2.5-meter telescope at Apache Point Observatory in New Mexico.

The combined dataset covers 1.5 million stars across the Milky Way Mapper and Black Hole Mapper programs. Among the stellar finds are the first carbon-enhanced metal-poor stars identified in the Magellanic Clouds and the first intermediate-mass stripped star, both long-sought objects that inform models of stellar formation and evolution.

The Black Hole Mapper portion grew three- to four-fold over the previous release, delivering roughly 1.1 million optical spectra representing about 500,000 distinct targets. Programs such as All-Quasar Multi-Epoch Spectroscopy and Reverberation Mapping repeatedly observe quasars to measure how supermassive black holes and their immediate environments change over time.

DR20 also integrates the first large coordinated dataset from the eROSITA X-ray all-sky survey through the SPIDERS program, providing optical identifications and redshifts for hundreds of thousands of X-ray sources, including active galactic nuclei, galaxy clusters, and active stars.

The Local Volume Mapper expanded from a single-tile preview to integral field spectroscopy maps of six target regions spanning 169 tiles and roughly 300,000 spectra. These maps capture Galactic H II regions, planetary nebulae, and nearby galaxies at high spatial resolution, including detailed views of the Rosette and Orion nebulae.

To help researchers navigate the data, the collaboration released LVMvis, an interactive browser-based tool with an RGB emission-line map of glowing gas, alongside updated interfaces Zora and Valis. Eighteen new or revised Value-Added Catalogs organize specialized measurements drawn from the survey data.

All DR20 data are cumulative, including every earlier SDSS phase, and are openly accessible via the Science Archive Server with server-side Python notebooks on SciServer Compute. The survey is funded by the Alfred P. Sloan Foundation, Heising-Simons Foundation, National Science Foundation, and participating institutions, with operations managed by the Astrophysical Research Consortium.