An international team led by the Max Planck Institute for Extraterrestrial Physics (MPE) has discovered three actively feeding supermassive black holes inside a single galaxy more than 12.5 billion light-years from Earth.

The galaxy, J0148-4214, is seen as it existed just 1.2 billion years after the Big Bang, thanks to a measured redshift of z=5.02. All three black holes are accreting matter from surrounding disks of gas.

Two sit near the galactic center, separated by a projected distance of only 620 light-years, while the third lies about 5,500 light-years out. According to MPE's Hannah Übler, this is the first evidence of three active black holes in one galaxy in the distant Universe.

Finding one active black hole at this distance is rare; finding three, all feeding, in the same galaxy is unprecedented.

Outlets report the finding as evidence that processes in the early Universe were efficient at bringing massive black holes together — precisely the setup for the merger events future gravitational wave observatories expect to detect.

The two central black holes are expected to merge within the next few hundred million years, and co-author Roberto Maiolino of the University of Cambridge says black hole merging may be an additional, fast route for rapid growth in the early Universe, potentially explaining how some cosmic giants became so enormous so quickly.

The black holes betrayed themselves through distinctive patterns in the light of hydrogen gas, which moves at extreme speeds under their gravitational pull, leaving recognizable spectral signatures.

The complicated hydrogen emission at the galaxy's center was best explained by two closely spaced black holes rather than one.

Using spectro-astrometry, the team tracked subtle shifts in the positions of spectral emissions to pinpoint both central objects even though the telescope could not resolve them as separate points of light.

Webb's Near Infrared Spectrograph in integral field spectroscopy mode (NIRSpec-IFS) was essential — without that spatial detail, astronomers likely would have identified only one of the three.

The three black holes differ dramatically in size: roughly 80 million, 600,000, and 2 million solar masses.

Surprisingly, the largest is not the most aggressive feeder — the 600,000-solar-mass black hole is growing so fast that its estimated accretion rate exceeds the Eddington limit, the maximum predicted by basic models of black hole growth.

That overfeeding may hold clues to how some black holes ballooned in the brief window of the early Universe.

MPE's Giovanni Mazzolari notes the JWST data also let the team estimate the galaxy's total stellar mass at about 1.3 billion suns, with the black holes representing a significant fraction of that.

The eventual collision of the two central black holes could produce an even more massive object, illustrating a process that may have been essential to building the earliest cosmic giants.

The distant third black hole presents a puzzle: it could be a remnant of an earlier merger flung outward by gravitational recoil — a kick caused when merging black holes emit gravitational waves unevenly — or it may be drifting toward the center to eventually interact with the other two.

Because multi-black-hole systems have likely gone undetected elsewhere, finding more could help scientists reconstruct the merger history behind the Universe's most massive black holes.