Chandra finds black hole that’s growing at 2.4 times the Eddington limit
Astronomers have uncovered one of the fastest-growing black holes ever observed, thanks to NASA’s Chandra X-ray Observatory. This discovery may help explain how some black holes reached enormous sizes so quickly after the Big Bang.
The black hole, named RACS J0320-35, has a mass of about one billion Suns and lies 12.8 billion light-years away. Astronomers are seeing it as it existed only 920 million years after the universe began. Remarkably, it is producing more X-rays than any other black hole yet discovered from the universe’s first billion years.
Quasar RACS J0320-35: A Cosmic Beacon of Extreme Brightness
This black hole powers a quasar—a dazzling, energetic object that can outshine entire galaxies. Its brilliance comes from torrents of matter spiraling inward and heating up before plunging into the black hole. The discovery raises a pressing question: How can such a monster grow so fast in such a short time?
Although researchers first spotted RACS J0320-35 two years ago, only Chandra’s 2023 X-ray observations revealed what makes it so extraordinary: the black hole appears to be growing 2.4 times faster than the Eddington limit, the theoretical maximum rate for black hole growth.
What Is the Eddington Limit—and Why Does It Matter?
When matter falls toward a black hole, it heats up and radiates energy across the spectrum, including optical light and X-rays. This intense radiation pushes outward against infalling matter. At the so-called Eddington limit, the outward radiation pressure should balance the inward pull of gravity, halting faster growth.
Yet RACS J0320-35 defies this principle. As lead author Luca Ighina of the Center for Astrophysics | Harvard & Smithsonian explained:
“It was a bit shocking to see this black hole growing by leaps and bounds.”
This suggests the black hole is feeding in ways scientists have rarely witnessed—challenging established theories about early black hole formation.
Did This Black Hole Start Small or Massive?
The mystery deepens when scientists ask how RACS J0320-35 began its life. Black holes growing at or below the Eddington limit must be born already large—at least 10,000 solar masses—to reach a billion Suns within the universe’s first billion years. Such “massive seed black holes” could arise from the direct collapse of a dense, pristine gas cloud with unusually few heavy elements. But these extreme conditions may be rare.
If instead RACS J0320-35 has truly grown well beyond the Eddington limit, it may have started in a more familiar way: from the collapse of a single massive star, perhaps less than 100 solar masses. Co-author Alberto Moretti of INAF-Osservatorio Astronomico di Brera noted:
“By knowing the mass of the black hole and working out how quickly it’s growing, we’re able to estimate how massive it could have been at birth.”
This ability to “rewind the clock” allows astronomers to test competing theories of how the earliest black holes were born.
Chandra X-ray Data Confirms Rapid Growth Models
To calculate how fast this black hole is feeding—somewhere between 300 and 3,000 Suns per year—astronomers compared theoretical models with Chandra’s detailed X-ray spectrum. The results closely matched predictions for a black hole growing beyond the Eddington limit.
Additional data from optical and infrared telescopes backed up the interpretation, strengthening the case that RACS J0320-35 is indeed defying conventional growth limits.
Black Holes, Cosmic Jets, and a New Mystery
The discovery also highlights another cosmic enigma: relativistic jets—streams of particles traveling near light speed—are blasting away from this quasar. Such jets are unusual for quasars, raising an intriguing question: Could rapid, super-Eddington growth be fueling the creation of these jets?
Co-author Thomas Connor from the Center for Astrophysics summed up the stakes:
“How did the universe create the first generation of black holes? This remains one of the biggest questions in astrophysics, and this one object is helping us chase down the answer.”
A Global Effort to Unlock the Secrets of RACS J0320-35
The discovery of this extraordinary quasar was possible thanks to a combination of cutting-edge observatories. It was first detected in a radio survey with the Australian Square Kilometer Array Pathfinder (ASKAP), then studied with the Dark Energy Camera in Chile. Follow-up observations with the Gemini-South Telescope pinned down its distance, while Chandra’s X-ray vision revealed the black hole’s astonishing growth rate.
What This Discovery Means for the Universe’s Dark Origins
By breaking the long-held assumption that black holes cannot exceed the Eddington limit for extended periods, RACS J0320-35 forces scientists to rethink how the earliest cosmic giants formed. Did the universe favor rare, massive seeds—or can ordinary black holes, born from collapsing stars, grow rapidly enough to become titans?
This black hole, shining across 12.8 billion light-years, may hold the key to one of astronomy’s most profound mysteries.
Source: Chandra finds black hole that’s growing at 2.4 times the Eddington limit
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Chandra finds black hole that’s growing at 2.4 times the Eddington limit