A team of scientists discovered that a black hole is expanding at one of the quickest speeds ever measured. This finding, made by scientists at the Center for Astrophysics using NASA's Chandra X-ray Observatory, might help explain how some black holes can attain huge masses so fast after the Big Bang. The study was published in The Astrophysical Journal Letters.
In the artist's illustration, the quasar, RACS J0320-35, sits at our upper left, filling the left side of the image. It resembles a spiraling, motion-blurred disk of orange, red, and yellow streaks. At the center of the disk, surrounded by a glowing, sparking, brilliant yellow light, is a black egg shape. This is one of the fastest-growing black holes ever detected. The black hole is also shown in a small Chandra X-ray image inset at our upper right. In that depiction, the black hole appears as a white dot with an outer ring of neon purple. The artist's illustration also highlights a jet of particles blasting away from the black hole at the center of the quasar. The streaked silver beam starts at the core of the distant quasar, near our upper left, and shoots down toward our lower right. The blurry beam of energetic particles appears to widen as it draws closer and exits the image. Image Credit: X-ray: NASA/CXC/INAF-Brera/L. Ighina et al.; Illustration: NASA/CXC/SAO/M. Weiss; Image Processing: NASA/CXC/SAO/N. Wolk
The black hole weighs around a billion times the mass of the Sun and is located approximately 12.8 billion light-years away from Earth, implying that scientists are just seeing it 920 million years after the universe began. It emits more X-rays than any other black hole observed during the first billion years of the universe.
The black hole powers a quasar, which is an extraordinarily bright object that can outshine whole galaxies. Large volumes of matter funneling around and into the black hole provide the power for this glowing monster.
While the same team detected it two years earlier, it took Chandra measurements in 2023 to determine what distinguishes this quasar, RACS J0320-35. The X-ray results show that this black hole appears to be expanding at a rate that surpasses the typical limit for such objects.
It was a bit shocking to see this black hole growing by leaps and bounds.
Luca Ighina, Study Lead, Center for Astrophysics
As matter is pulled toward a black hole, it heats up and emits intense radiation across a broad spectrum, including X-rays and visible light. This radiation exerts pressure on the infalling material. When the pace of infalling matter reaches a critical point, the radiation pressure balances the black hole's gravity, and matter cannot fall inwards any faster. That maximum is known as the Eddington limit.
Scientists believe that black holes that grow slower than the Eddington limit must be born with masses of 10,000 Suns or more to attain a billion solar masses within a billion years of the Big Bang, as witnessed in RACS J0320-35. A black hole with such a large birth mass might occur directly from an exotic process: the collapse of a massive cloud of dense gas having very low concentrations of elements heavier than helium, which could be extremely rare.
If RACS J0320-35 is indeed growing rapidly, at an estimated 2.4 times the Eddington limit, and has sustained this rate over a long period, it’s possible the black hole formed through a more typical process. In this scenario, it could have originated with a mass under 100 times that of the Sun, likely resulting from the collapse of a massive star.
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, Study Co-Author, INAF-Osservatorio Astronomico di Brera
To determine how rapidly this black hole is developing (between 300 and 3,000 Suns each year), the researchers compared theoretical models to Chandra's X-ray signature, or spectrum, which shows the number of X-rays at various energies.
They discovered that the Chandra spectrum closely matched what they expected from models of black holes expanding faster than the Eddington limit. Data from optical and infrared light further support the conclusion that this black hole is gaining weight faster than the Eddington limit allows.
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.
Thomas of Connor, Study Co-Author, Center for Astrophysics
The cause of particle jets that go out from some black holes at almost the speed of light, as observed in RACS J0320-35, is another scientific enigma that this result attempts to solve. This type of jet is uncommon for quasars, which might indicate that the black hole's fast development rate is somehow causing these jets to form.
Along with optical data from the Dark Energy Camera, an instrument mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile, the quasar was previously found as part of a radio telescope survey using the Australian Square Kilometer Array Pathfinder.
The precise distance of RACS J0320-35 was determined using the Gemini-South Telescope at the U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory on Cerro Pachon, Chile.
Journal Reference:
Ighina, L., et al. (2025) X-Ray Investigation of Possible Super-Eddington Accretion in a Radio-loud Quasar at z = 6.13. The Astrophysical Journal Letters. doi.org/10.3847/2041-8213/aded0a