The Sloan Digital Sky Survey (SDSS) announced Data Release 20 (DR20), adding optical spectra from the southern hemisphere and expanding the Black Hole Mapper catalog to include over 500,000 supermassive black holes.

The Black Hole Mapper, part of SDSS‑V, coordinates optical observations with X‑ray data from the eROSITA mission to identify and measure redshifts of accreting supermassive black holes across cosmic time.

DR20 provides more than 3.3 million optical spectra from 500,000 galaxies and 1.5 million stars, and includes the first BOSS spectra taken at Las Campanas Observatory in Chile. The SPIDERS program matches eROSITA X‑ray sources with SDSS spectra, delivering redshifts for about 200,000 X‑ray targets, the largest uniform spectroscopic sample of X‑ray emitters. Multi‑epoch observations enable reverberation mapping to measure black‑hole masses and track changes in quasars over years.

The open data set will enable researchers to study early‑universe black‑hole growth, the fraction of hidden black holes, and the connection between dust‑enshrouded phases and total mass accumulation. Dr. Andrea Merloni said the combination of X‑ray and optical data opens new scientific perspectives.