In the early universe, astronomers found a rare light that breaks the rules of how black holes grow. Researchers from Waseda University and Tohoku University, working with the Subaru Telescope, have uncovered a quasar, J084222.9+001000 (hereafter ID830), a cosmic powerhouse that existed nearly 12 billion years ago.
This quasar is no ordinary find. In the eFEDS field, it shines as the brightest X-ray quasar among those that also emit strong radio waves, marking it as a truly exceptional object in the cosmic landscape.
Astronomers have long wrestled with one of astronomy’s deepest mysteries: how supermassive black holes (SMBHs) grew so massive so quickly, and how their host galaxies assembled stars alongside them. The discovery of quasars powered by SMBHs in the early universe already strains the standard theories of black hole formation.
Recent breakthroughs from the James Webb Space Telescope (JWST) have only deepened the puzzle, revealing active galactic nuclei (AGNs) at even earlier times. These findings suggest that giant black holes appeared much sooner than current models predict, forcing scientists to rethink the timeline of cosmic evolution.
Normally, black holes are thought to obey a feeding speed limit known as the Eddington limit. Yet some black holes have been caught breaking this rule, in a process called super-Eddington accretion. This allows them to grow at astonishing rates, offering a possible explanation for the existence of massive black holes in the universe’s infancy.
Quasar ID830 is one such rebel. By combining data from SDSS and Subaru’s MOIRCS, covering ultraviolet to optical light, along with a full energy profile from radio waves to X-rays, the team built a detailed picture of this quasar.
Their analysis revealed that ID830 was in a super-Eddington accretion stage 12 billion years ago, devouring matter at a rate 13 times faster than the theoretical limit. If confirmed, this would make it the fastest-growing supermassive black hole of its kind ever observed.
Lead author Sakiko Obuchi emphasized the importance of this discovery: “This discovery may help elucidate the formation process of supermassive black holes in the early universe, which has been difficult to understand until now. In the future, we hope to explore the mechanisms of X-ray and radio wave emission from this quasar and determine whether there are any similar objects yet to be discovered.”
What makes ID830 even more remarkable is its dual brilliance. During super-Eddington accretion, theory predicts that the hot gas around a black hole should cool efficiently, dimming X-rays and weakening radio jets. Yet ID830 defies expectations; it blazes in both X-rays and radio waves simultaneously.
This anomaly hints at a hidden mechanism not yet understood, one that could reshape how scientists think about black hole growth.
The team proposes that the quasar’s bright X-rays may result from sudden bursts of growth. In the early universe, some black holes feasted in sudden banquets. When stars or gas clouds plunged in, they devoured matter at impossible speeds, blazing with X-rays before returning to calm. During these bursts, both super-Eddington accretion and strong X-ray emission can occur together.
If this scenario is correct, ID830 would represent the first evidence of a supermassive black hole’s growth rate fluctuating in the early universe.
The quasar’s strong radio jets add to its mystery. These jets could stop new stars from forming in their galaxy, changing how the galaxy grows. Scientists don’t yet know how super-Eddington accretion connects to jet activity, but ID830 gives a rare look at how black holes and galaxies grew together in the early universe.
Journal Reference:
Sakiko Obuchi et al, Discovery of an X-Ray Luminous Radio-loud Quasar at z= 3.4: A Possible Transitional Super-Eddington Phase, The Astrophysical Journal (2026). DOI: 10.3847/1538-4357/ae1d6d