Imagine looking so far into space that you are also looking back in time—almost to the dawn of the universe itself. Now imagine discovering, within that ancient light, a cosmic monster devouring matter at a rate that defies the rules of physics as we know them. This is exactly what astronomers have found in the distant quasar known as RACS J0320-35, a black hole that has become one of the fastest-growing ever observed.
Located about 12.8 billion light-years away, we are seeing this black hole as it was just 920 million years after the Big Bang. That means the universe was less than 7% of its current age when this enormous object was already thriving. Weighing in at about a billion times the mass of the Sun, RACS J0320-35 is not only massive but also alarmingly hungry—swallowing hundreds to thousands of suns’ worth of material each year. Its extreme behavior may hold the key to solving one of astronomy’s biggest mysteries: how black holes in the early universe grew so unimaginably large, so quickly.
A Quasar That Outshines Galaxies
The central black hole of RACS J0320-35 is hidden by distance and darkness, but its presence is betrayed by the quasar it powers. A quasar is an incredibly bright beacon fueled by a black hole feeding on matter. As gas and dust spiral toward the black hole, they form an accretion disk that heats up to millions of degrees, blasting out light across the electromagnetic spectrum—from radio waves to X-rays.
RACS J0320-35 is producing more X-rays than any other black hole observed from the first billion years of cosmic history. To put this in perspective, its brilliance outshines entire galaxies, flooding space with radiation that began its journey billions of years ago, only now reaching our telescopes.
This quasar’s glow is not merely a spectacle. It is a cosmic clue. Its intense X-ray signature, observed by NASA’s Chandra X-ray Observatory, suggests the black hole is breaking through what astrophysicists long thought was a natural growth limit.
The Breaking of the Cosmic Limit
When matter falls toward a black hole, it doesn’t disappear quietly. Friction and compression heat it up, producing staggering amounts of energy. At a certain point, the radiation pressure from this energy pushes back against incoming material, limiting how fast the black hole can feed. This limit is known as the Eddington limit, a kind of cosmic speed cap on black hole growth.
But RACS J0320-35 appears to be different. The new observations suggest it is growing at 2.4 times the Eddington limit, defying the rules. If this has been happening for a significant stretch of time, it changes everything scientists thought they knew about black hole formation.
“It was a bit shocking to see this black hole growing by leaps and bounds,” said Luca Ighina of the Center for Astrophysics | Harvard & Smithsonian, the lead author of the study. His team’s findings, published in The Astrophysical Journal Letters, raise the possibility that supermassive black holes may not need extraordinary birth conditions to become the giants we see today.
Rethinking the Birth of Cosmic Monsters
For years, astronomers puzzled over how black holes reached billions of solar masses so soon after the Big Bang. One theory suggested that the seeds of these giants had to be enormous from the start—perhaps formed by the direct collapse of colossal gas clouds. Such “heavy seeds” could have been tens of thousands of times the mass of the Sun at birth, skipping the smaller stages of growth.
But if RACS J0320-35 really has been feeding faster than the Eddington limit, it might have started from a far more modest seed, perhaps the death of a single massive star only about a hundred times the mass of the Sun. From there, rapid growth could explain how it ballooned into a billion-solar-mass giant within 920 million years.
“By knowing the mass of the black hole and working out how quickly it’s growing, we’re able to work backward to estimate how massive it could have been at birth,” explained co-author Alberto Moretti of INAF-Osservatorio Astronomico di Brera. With this information, astronomers can now test competing theories of black hole origins.
Feeding at Cosmic Speed
So how much is this black hole consuming? Calculations suggest it is devouring between 300 and 3,000 solar masses of material every year. That’s like swallowing hundreds to thousands of suns annually—a diet unmatched by most black holes known.
Researchers confirmed this furious appetite by comparing the observed X-ray spectrum from Chandra with theoretical models. The results lined up almost perfectly with the expectations for a black hole growing faster than the Eddington limit. Optical and infrared observations supported this interpretation, painting a consistent picture of runaway growth.
The Mystery of Black Hole Jets
As if its growth rate weren’t remarkable enough, RACS J0320-35 has another surprise: it is producing jets of particles shooting into space at nearly the speed of light. Such jets are not common among quasars, especially in the early universe. Their presence here raises intriguing questions. Could the rapid feeding itself be fueling the creation of these jets? If so, this discovery may reveal an important link between how black holes grow and how they shape the galaxies around them.
A Cosmic Collaboration
The story of RACS J0320-35 is also a story of collaboration between telescopes across the globe and in space. It was first identified in a radio survey by the Australian Square Kilometer Array Pathfinder. Its distance was then confirmed with the Gemini-South Telescope in Chile, while the Dark Energy Camera helped pinpoint its optical signature. Finally, Chandra’s powerful X-ray eyes revealed the extraordinary pace of its growth, setting it apart from other quasars of its era.
Each instrument contributed a piece of the puzzle, weaving together a clearer picture of this ancient black hole’s extraordinary life.
Chasing the First Black Holes
“How did the universe create the first generation of black holes?” asked Thomas Connor, a co-author of the study. “This remains one of the biggest questions in astrophysics and this one object is helping us chase down the answer.”
Indeed, discoveries like RACS J0320-35 push the boundaries of what we know about cosmic history. They force us to rethink the rules of growth, the conditions of the early universe, and the interplay between matter, energy, and gravity.
For now, RACS J0320-35 stands as both a mystery and a beacon. It tells us that the universe, even in its youth, was more dynamic and surprising than we once believed. It reminds us that the cosmos is not a quiet, orderly place but a stage where forces of unimaginable power shape everything we see today.
More information: Luca Ighina et al, X-Ray Investigation of Possible Super-Eddington Accretion in a Radio-loud Quasar at z = 6.13, The Astrophysical Journal Letters (2025). DOI: 10.3847/2041-8213/aded0a
