Three active black holes found in a galaxy 12.5 billion years away

That detail let the team distinguish two central objects even though Webb could not resolve them as two separate points of light. The same observations exposed the third active black hole in the outer region. Without this information, the team likely would have identified only one.

Takeaway: Detailed mapping of a galaxy's spectra can reveal several black holes hidden in one combined signal.

Why is the smaller black hole growing so fast?

The biggest is not the fastest. The 80-million-Sun black hole feeds less aggressively than its neighbor, whose mass is roughly 600,000 Suns.

The smaller object's estimated matter intake exceeds the Eddington limit, the highest rate predicted by basic models of black-hole growth. That excess may offer clues to how some black holes became extraordinarily massive during the relatively short time available in the early universe.

Giovanni Mazzolari, the second author and an MPE researcher, said Webb data allowed the team to estimate the three masses, their accretion rates, meaning how quickly they took in matter, and the galaxy's stellar mass. Those results put the galaxy's stars at about 1.3 billion solar masses and show that the black holes represent a significant fraction of that total.

Takeaway: A black hole of about 600,000 Suns may be growing faster than basic models allow.

What happens next?

The two central black holes are expected to merge within the next few hundred million years. Their collision could create a still more massive central black hole. Astronomers think such mergers may have helped some black holes reach enormous sizes soon after the Big Bang.

Galaxy collisions were common in the early universe. When galaxies combined, their central black holes could move closer and eventually merge, producing increasingly massive black holes at the centers of the new galaxies.

Übler said the system suggests that early-universe processes efficiently brought massive black holes together, setting the stage for mergers that future gravitational-wave observatories should detect. Such observatories measure spacetime ripples produced by massive objects in motion.

The outer black hole has two possible histories. It could be a remnant of an earlier merger, pushed outward by gravitational recoil. That kick can occur when merging black holes emit gravitational waves unevenly, sending the resulting black hole in the opposite direction.

Alternatively, the outer object may be moving toward the center, where it could eventually interact with the central pair.

Roberto Maiolino, a University of Cambridge professor and co-author, said: "These results are extremely exciting." He added: "They suggest that black hole merging may be an additional, fast route for their rapid growth in the early Universe."

Takeaway: The central pair is expected to merge, while the outer black hole's origin remains uncertain.

How much does one system establish?

One galaxy is not a population. The result rests on a single system, and the masses, feeding rates and merger timetable rely on calculations rather than direct images of the black holes.

It nevertheless provides evidence that three active black holes can exist in one early galaxy. The finding also suggests that other distant galaxies may contain multiple growing black holes that less detailed observations would miss. More examples could help reconstruct the history of black-hole mergers and explain how the universe produced its most massive black holes so early.

The results appear in the 2026 journal Astronomy as "BlackTHUNDER: Evidence of three massive black holes in a z ∼ 5 galaxy," volume 712, article A80, DOI 10.1051/0004-6361/202557419.

Takeaway: The discovery establishes a target for future surveys, not a frequency for three-black-hole galaxies.