Astronomers have made an astonishing discovery: a black hole that is growing at an unprecedented rate.
An international collaboration of astronomers, spearheaded by researchers from Waseda University and Tohoku University, has uncovered a fascinating quasar in the early Universe housing one of the most rapidly expanding supermassive black holes identified to date. Utilizing data from the Subaru Telescope, they revealed a striking combination of characteristics. This quasar is not only absorbing matter at an incredible speed but also emitting intense X-rays and producing a powerful radio jet. These attributes are typically believed to be mutually exclusive according to many existing theories, which makes this object a remarkable and enlightening find. The observations shed new light on the mechanisms behind the swift growth of supermassive black holes during the formative years of the Universe.
Supermassive black holes, which can weigh millions to billions of times more than our Sun, are found at the centers of most galaxies. They grow in size by attracting surrounding gas. As this gas spirals towards the black hole, it forms a rotating disk known as an accretion disk, resulting in a concentrated area of extremely hot plasma called a corona—this region is a primary source of X-ray emissions. In some instances, the system also generates a narrow jet that is particularly bright in radio wavelengths. When these black holes are actively consuming material and shining exceptionally brightly, they are classified as quasars. A critical question remains unanswered: how did some of these colossal entities achieve such massive sizes so early in cosmic history?
Challenging the Limits of Black Hole Growth
One potential explanation for this rapid growth in the early Universe is the phenomenon known as super-Eddington accretion. Under normal circumstances, the radiation generated by infalling material exerts an outward pressure that limits the growth rate of a black hole; this upper boundary is referred to as the Eddington limit. However, certain extreme conditions may permit black holes to surpass this limit temporarily, resulting in dramatically accelerated mass increases.
To determine if this type of accelerated growth occurred in the early Universe, the research team employed the near-infrared spectrograph (MOIRCS) on the Subaru Telescope. By observing the motion of gas around the quasar and examining the emission line of Mg II (2800 Å), they calculated the mass of the black hole. Their findings indicate that this supermassive black hole existed around 12 billion years ago and is currently accreting matter at approximately 13 times the Eddington limit, as measured through X-ray observations.
A Quasar That Breaks the Mold
What distinguishes this quasar is its behavior across different wavelengths of light. Many theoretical models predict that during a phase of super-Eddington growth, alterations in the internal structure of the accretion flow should decrease X-ray emissions and diminish jet activity. Contrary to these predictions, this quasar continues to emit strong X-rays while simultaneously being very radio-bright. The results suggest that the black hole is experiencing extraordinary growth while maintaining an active corona and a robust jet. This unexpected combination indicates that the physical processes governing these phenomena are not entirely understood by current models.
The research team hypothesizes that the quasar is being observed during a brief transitional phase, possibly following a sudden influx of gas. In this case, a rapid surge in available material propels the black hole into a super-Eddington state. For a limited duration, both the X-ray-emitting corona and the radio jet remain highly energized before the system gradually returns to a more typical growth pattern.
If this interpretation holds true, this quasar presents a rare opportunity to study the dynamics of black hole growth over time in the early Universe, a significant step toward unraveling how supermassive black holes formed so rapidly.
Implications for Galaxy Evolution
The powerful radio signal emitted by the jet signifies that it carries sufficient energy to impact its surroundings. Such jets can heat or disrupt gas within their host galaxies, potentially influencing star formation and shaping the co-evolution of galaxies and their central black holes. The link between super-Eddington growth and feedback from jets is still poorly understood, making this quasar a valuable point of reference for testing emerging theories.
Lead author Sakiko Obuchi from Waseda University emphasizes:
"This discovery might bring us closer to grasping how supermassive black holes formed so swiftly in the early Universe. We are eager to explore what drives the unusually strong X-ray and radio emissions and whether similar objects have been overlooked in previous survey data."
The findings were published under the title "Discovery of an X-ray Luminous Radio-Loud Quasar at z = 3.4: A Possible Transitional Super-Eddington Phase" in the Astrophysical Journal on January 21, 2026.
This research was made possible thanks to grants from the Grants-in-Aid for Scientific Research (Grant Nos. 25K01043, 23K13154, 22H00157), the JST FOREST Program (JPMJFR2466), and funding from the Inamori Foundation.
The Subaru Telescope, a prominent optical-infrared observatory, is operated by the National Astronomical Observatory of Japan, part of the National Institutes of Natural Sciences, with backing from the MEXT Project aimed at promoting large scientific advancements. The team acknowledges and respects the cultural, historical, and natural significance of Maunakea in Hawai`i, where these observations were conducted.
