Twelve point nine billion years ago — less than a billion years after the Big Bang — some of the most massive galaxies in the universe were already beginning to die.

Using the Subaru Telescope and the James Webb Space Telescope, astronomers have discovered supermassive black holes actively feeding at the centers of these early galaxies. These black holes, shining as bright quasars, revealed something surprising: their host galaxies had already built up tens of billions of stars… but their star formation was shutting down.

Two quasars, known as J2236+0032 and J1512+4422, were studied in detail. Each hosts a black hole at its core, while their galaxies contain up to 60 billion solar masses in stars. Yet JWST observations showed that new stars had nearly stopped forming — the galaxies were transitioning into a quiescent phase.

Astronomers believe the intense radiation from these central black holes may have shut down star formation, essentially starving the galaxies of new life. This is direct evidence of the long-hypothesized co-evolution between galaxies and their central black holes — a process where black holes don’t just grow with their galaxies, but actively shape their fate.

As lead author Masafusa Onoue put it: “It was totally unexpected to find such mature galaxies so early in the universe — and even more remarkable that they still host active black holes.”

This discovery gives us a glimpse of cosmic history in action — catching galaxies in the very moment they begin to die, while their black holes blaze at their brightest.