Deep in the distant universe, astronomers have found a black hole that seems to be breaking the usual rules for how fast these cosmic beasts can grow.
The object, called RACS J0320-35, is so far away that its light has traveled 12.8 billion years to reach us, meaning we see it as just 920 million years after the Big Bang.
Even at that early time, the black hole had already tipped the scales at about a billion times the mass of the Sun, and it shone in X-rays more brightly than any other black hole found in the universe’s first billion years.
Together, these facts reveal a surprising story. The black hole appears to be devouring matter much faster than the normal theoretical limit. “It was a bit shocking to see this black hole growing by leaps and bounds,” Luca Ighina, author of the study on RACS J0320-35, said.
Catching a giant cosmic anomaly
The research began with a bright, distant object known as RACS J0320-35, first flagged in a large radio survey using the Australian Square Kilometre Array Pathfinder (ASKAP).
Follow-up observations with telescopes in Chile, including the Dark Energy Camera and the Gemini South Telescope, confirmed its distance and revealed it was a quasar, a galaxy powered by a supermassive black hole devouring gas and shining so brightly it outshines entire galaxies.
However, it wasn’t until Chandra’s X-ray observations in 2023 that astronomers realized what made this quasar different. When matter falls into a black hole, it heats up and emits light, including powerful X-rays.
Normally, this process is limited by something called the Eddington limit—a balance point where the outward push of radiation prevents more material from falling in. Think of it as a natural speed cap on how fast a black hole can grow. Surprisingly, the data showed that RACS J0320-35 is breaking this cosmic speed cap.
The black hole appears to be growing at about 2.4 times the Eddington limit, which means it is consuming the equivalent of 300 to 3,000 Suns’ worth of material every year. This is the fastest rate ever seen for a black hole in the first billion years of the universe.
What does this growth mean?
Until now, astronomers thought the only way early black holes could reach a billion solar masses was if they were born already huge, about 10,000 times the mass of the Sun, from the direct collapse of giant, pristine gas clouds.
However, if RACS J0320-35 has indeed been feasting at such extreme rates for long periods, it could have started much smaller, with a mass under 100 Suns, like the black holes formed from the deaths of massive stars. That would open up a new path for explaining how these cosmic giants came to be.
“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. With this calculation, we can now test different ideas on how black holes are born,” Alberto Moretti, one of the study authors and a researcher at INAF-Osservatorio Astronomico di Brera in Italy, said.
Additionally, this quasar is also producing jets of particles moving at nearly the speed of light, a rare feature among quasars. The researchers suspect its unusually fast growth might be linked to the creation of these jets.
Therefore, this discovery is more than just a record-breaker. It challenges long-held theories about the birth and growth of black holes and could reshape our understanding of how the early universe evolved.
If black holes can grow this quickly, scientists may not need to invoke exotic, rare conditions to explain the existence of billion-solar-mass black holes so soon after the Big Bang. Instead, ordinary black holes formed from collapsing stars might have had a chance to bulk up rapidly under the right conditions.
However, a big question that remains is whether RACS J0320-35 really sustains this extreme growth for hundreds of millions of years, or is it just going through a short-lived feeding frenzy? Also, how exactly are its powerful jets tied to this rapid growth?
To find answers, astronomers plan to look for and study more rule-breaking quasars with the help of Chandra and upcoming observatories.
The study is published in the Astrophysical Journal Letters.