Overview

• RACS J0320-35 hosts a roughly billion-solar-mass black hole seen 12.8 billion light-years away, about 920 million years after the big bang.
• Chandra spectroscopy matches models of super-Eddington accretion at about 2.4 times the classical limit, implying growth of roughly 300–3,000 solar masses per year.
• It emits more X-rays than any other black hole known from the universe’s first billion years and is radio-loud with detected relativistic jets.
• The source was first flagged in an ASKAP RACS radio survey, with DECam imaging and Gemini-South spectroscopy establishing the redshift before Chandra’s 2023 X-ray measurements.
• Findings accepted in The Astrophysical Journal Letters, led by Luca Ighina, inform debates over seed formation by supporting either rapid super-Eddington growth from small seeds or rarer massive direct-collapse origins.