SDSS Data Release 20 Maps Half a Million Supermassive Black Holes — 70–90% of Their Growth Happened Behind Dust
The Sloan Digital Sky Survey's Black Hole Mapper Data Release 20, published July 30, 2026, contains over 3.3 million optical spectra covering 500,000 galaxies, 1.5 million stars, and roughly 200,000 X-ray targets from the SPIDERS program, gathered with the Sloan 2.5m at Apache Point and the du Pont 2.5m at Las Campanas using BOSS spectrographs and robotic focal plane systems. The headline scientific result is that 70% to 90% of all supermassive black hole growth occurred behind heavy veils of dust and gas. Data is free via the Science Archive and Catalog Archive Servers, SciServer Compute, and SQL, with value-added catalogs and Jupyter tutorials — a large, clean, openly queryable corpus. It drew 172 points and 38 comments.
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