Astronomers have taken a rare look into the distant past of the universe and uncovered evidence that galaxies and their central black holes were already shaping each other just 900 million years after the Big Bang.
By combining the wide-field survey power of Japan’s Subaru Telescope with the sharp infrared vision of the James Webb Space Telescope (JWST), researchers discovered two massive galaxies whose stars are fading while their supermassive black holes remain fiercely active.
Every large galaxy is thought to harbor a supermassive black hole at its core, weighing millions or even billions of times more than our Sun.
When these black holes are actively consuming surrounding gas, they blaze as quasars—among the brightest objects in the universe.
In nearby galaxies, scientists have long noted a strong link between the size of a galaxy and the mass of its black hole, suggesting they grow together in a process known as co-evolution.
But until now, it was unclear when this relationship began.
The new study focused on two quasars, J2236+0032 and J1512+4422, located 12.9 billion light-years away.
Using JWST’s Near Infrared Spectrograph, astronomers not only measured the intense light of the quasars themselves but also picked up faint absorption lines from stars within their host galaxies.
This allowed them to analyze the history of star formation in these ancient systems.
What they found was surprising. Both galaxies turned out to be enormous—containing tens of billions of solar masses in stars—yet their star-making days appear to be nearly over.
The data revealed that after a huge burst of star formation several hundred million years earlier, star birth had slowed dramatically or nearly stopped. Despite this, each galaxy still hosts a blazing quasar at its center.
“It was totally unexpected to find such mature galaxies less than a billion years after the Big Bang,” said Dr. Masafusa Onoue of the Kavli Institute for the Physics and Mathematics of the Universe and Waseda University.
“What is even more remarkable is that these ‘dying’ galaxies still contain very active supermassive black holes.”
The results suggest that the intense radiation and powerful winds from the black holes may have quenched star formation, shutting down their galaxies’ growth while the black holes themselves continued to thrive. This offers rare evidence of black holes directly influencing the evolution of their host galaxies in the early universe.
This discovery, published in Nature Astronomy, was made possible by the Subaru Telescope’s wide-area sky survey that first identified the quasars and JWST’s unmatched sensitivity to faint light from the distant cosmos.
By capturing this turning point in galaxy history, astronomers are gaining vital clues about how galaxies and black holes grew hand-in-hand during the universe’s first billion years.
