The Sloan Digital Sky Survey V has taken a major step toward mapping the sky on a truly global scale with Data Release 20. Known as DR20, the release includes the first optical (BOSS) SDSS-V spectra collected from the Southern Hemisphere, greatly expanding the survey beyond the groundwork established in earlier releases.
By combining these new southern observations with data gathered in the north, SDSS-V is bringing panoptic spectroscopy across both hemispheres. The result gives astronomers a broader view of stars, interstellar gas, and distant galaxies throughout the cosmos. DR20 contains part of the much larger panoptic spectroscopic map that the ongoing SDSS-V survey is continuing to build.
Studying both the nearby and distant Universe is essential for understanding the physical processes that shape it. DR20 advances that effort while moving SDSS-V further into an era of multi-wavelength, multi-epoch optical and infrared observations.
What Is New in Data Release 20?
DR20 includes a wide range of resources for researchers and astronomy enthusiasts. Among them are catalogs covering black holes, stars, and interstellar gas, along with new visualizations and scientific tools designed to help users explore the enormous dataset.
“DR20 represents an enormous leap in the scale of SDSS data products — today we release over three million spectra of stars and galaxies along with 18 value added catalogs,” said Dr. Emily Griffith of University of Colorado Boulder, spokesperson for the SDSS-V collaboration. “It’s the product of years of work by a dedicated, international team of astronomers. We’re excited to share DR20 with the world and see what the community discovers with it.”
First Southern Hemisphere BOSS Spectra
For the first time, DR20 includes SDSS-V stellar and extra-galactic optical spectra obtained in the Southern Hemisphere. These observations were made with the du Pont 2.5m Telescope at Las Campanas Observatory (LCO) in Chile and are combined with updated observations from the Sloan Foundation 2.5m Telescope at Apache Point Observatory (APO).
Together, the two observing sites greatly expand the geographic reach of the survey and allow SDSS-V to examine the sky from both hemispheres.
Connecting Optical and X-Ray Views of the Sky
DR20 also delivers the first large data stream from coordinated eROSITA-SDSS-V observations. This work is part of the SPectroscopic IDentification of ERosita Sources (SPIDERS) program and is coordinated with the second release of the eROSITA X-ray All-Sky Survey (eRASS DR2).
These observations provide important identifications and optical redshift measurements for hundreds of thousands of X-ray emitting active galactic nuclei (AGN), galaxy clusters, and active stars. By connecting X-ray detections with detailed optical measurements, researchers can better determine what these energetic objects are and where they are located in the Universe.
A Major Expansion of the Black Hole Mapper
The Black Hole Mapper (BHM) grows dramatically in DR20, with 3-to-4-fold more data than were available in DR19. The release contains approximately 1.1 million optical BOSS spectra representing roughly 500,000 distinct objects.
Along with the SPIDERS program, the expanded dataset includes major contributions from the All-Quasar Multi-Epoch Spectroscopy (AQMES) program and the Reverberation Mapping (RM) program. These projects repeatedly observe quasars and other targets to study how supermassive black holes and their surroundings change over time.
Mapping 1.5 Million Stars
The Milky Way Mapper (MWM) also receives a substantial expansion in DR20, adding a large collection of optical stellar targets.
Across the BHM and MWM surveys, DR20 contains more than 3 million spectra covering 1.5 million stars. The collection includes the first carbon-enhanced metal-poor stars identified in the Magellanic Clouds as well as the first intermediate-mass stripped star. Both types of objects have long been sought because they can provide important clues about how stars form and evolve.
New Spectral Maps of Nebulae and Nearby Galaxies
The Local Volume Mapper (LVM) has expanded far beyond the single-tile preview released with DR19. DR20 now includes integral field spectroscopy maps of 6 separate target regions covering 169 tiles and about 300,000 spectra.
These maps capture Galactic HII regions, planetary nebulae, and nearby galaxies at exceptional spatial scales. They also give researchers a new way to examine well-known objects such as the Rosette and Orion nebulae using detailed spectroscopic information spread across large areas of the sky.
A New Tool for Exploring Cosmic Gas
To help users navigate the growing Local Volume Mapper dataset, the collaboration has introduced LVMvis. The interactive, browser-based visualization tool complements the next-generation user interfaces (Zora and Valis) that were also updated for DR20.
LVMvis includes an RGB HiPS emission-line map that allows users to explore the distribution and structure of glowing gas across the sky.
DR20 also includes 18 brand-new or comprehensively updated Value-Added Catalogs (VACs). These catalogs are designed to make specialized scientific investigations easier by organizing and enhancing information derived from the main survey data.
Accessing the Universe
Like previous SDSS releases, DR20 is cumulative. It contains all newly reduced BOSS spectroscopic observations collected through February 2, 2025, from both hemispheres, together with spectroscopic data from every earlier phase of the Sloan Digital Sky Survey.
The full dataset is available through the Science Archive Server (SAS). Updated Python Notebook Tutorials that run server-side within SciServer Compute are also openly available to astronomers and members of the public under open-use principles.
“We want everyone to make use of the SDSS data products, whether they are a professional astronomer doing their research, a student learning how to work with data, a teacher looking for classroom material, or someone who is just interested in astronomy in general,” said Dr. Anne-Marie Weijmans of University of St Andrews, the SDSS Data Products Coordinator. “That is why we have so many different platforms for people to interact with the data, and we take care to provide numerous examples and tutorials for each of these. The data should not just be publicly available but be publicly usable.”
“This data release provides some spectacular SDSS-V data that we are sure people will make excellent use of,” said Dr. Juna Kollmeier of Carnegie Science, the SDSS-V Director. “But we aren’t stopping here. We just spent a week talking about what will go into DR21 and DR22! We’re going to need bigger computers!”
About the SDSS
Funding for the Sloan Digital Sky Survey V has been provided by the Alfred P. Sloan Foundation, the Heising-Simons Foundation, the National Science Foundation, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah.
SDSS telescopes are located at Apache Point Observatory, which is funded by the Astrophysical Research Consortium and operated by New Mexico State University, and at Las Campanas Observatory, which is operated by the Carnegie Institution for Science.
SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration, including Caltech, the Carnegie Institution for Science, Chilean National Time Allocation Committee (CNTAC) ratified researchers, The Flatiron Institute, the Gotham Participation Group, Harvard University, Heidelberg University, The Johns Hopkins University, L’Ecole polytechnique fédérale de Lausanne (EPFL), Leibniz-Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Extraterrestrische Physik (MPE), Nanjing University, National Astronomical Observatories of China (NAOC), New Mexico State University, The Ohio State University, Pennsylvania State University, Smithsonian Astrophysical Observatory, Space Telescope Science Institute (STScI), the Stellar Astrophysics Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Illinois at Urbana-Champaign, University of Toronto, University of Utah, University of Virginia, Yale University, and Yunnan University.
