Overview
- The discovery of 84 “hypersoft X‑ray sources” was published in Nature Astronomy on Sept. 9, 2026, after a reanalysis of low-energy channels in Chandra’s 1999–2017 archive.
- Researchers found objects that appear only at the very lowest X‑ray energies and infer they also emit large amounts of ultraviolet or extreme‑UV radiation that is mostly absorbed by intervening hydrogen and helium.
- The team proposes the sources are compact accreting binaries — white dwarfs, neutron stars, or black holes pulling gas from companions — but the exact mix of object types is not yet determined.
- The 84 sources sit in six external galaxies, including the spirals M31 and M101 and four ellipticals, and appear in both star-forming and older stellar regions, implying these systems occur in diverse environments.
- Scientists plan targeted follow-up observations to test the compact‑binary hypothesis and to measure how much unseen UV these systems add to galactic ionization, while noting direct study of their extreme‑UV output will remain limited by interstellar absorption.