Three Feeding Black Holes Found in One Galaxy 12.5 Billion Light-Years Away

Astronomers have found three actively feeding supermassive black holes in a single galaxy more than 12.5 billion light-years from Earth, according to ScienceDaily, which relayed a release from the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany. The lead researcher said it is the first evidence of three active black holes in one galaxy this far back in cosmic history.

Two of the black holes sit close together near the galaxy’s center and are expected to merge. A third is located much farther out. The finding gives scientists a rare look at how giant black holes grew and interacted when the universe was young.

The key numbers behind the discovery

• 12.5 billion light-years: the distance to the galaxy, known as J0148-4214. Its light has traveled for roughly that many years to reach Earth, so astronomers see it as it was 1.2 billion years after the Big Bang.
• z=5.02: the redshift the team measured, a stretching of light by cosmic expansion that is used to work out how far away a galaxy is.
• 620 light-years: the projected distance between the two black holes near the galaxy’s center.
• 5,500 light-years: roughly how far the third black hole lies from the center.
• 80 million, 600,000 and 2 million suns: the approximate masses the researchers calculated for the three black holes.
• 1.3 billion suns: the galaxy’s total stellar mass, according to second author Giovanni Mazzolari of MPE, who said the black holes make up a significant fraction of it.

How the team found black holes it could not see

The researchers used data from the James Webb Space Telescope (JWST). Gas falling toward a black hole moves at extreme speeds, and that motion leaves recognizable patterns in the light from hydrogen. In the galaxy’s center the team found an unusually complicated pattern that was best explained by two closely spaced black holes rather than one.

The telescope could not show the two as separate points of light. To tell them apart, the scientists used a technique called spectro-astrometry, which tracks small shifts in the position of spectral features across the galaxy. That revealed where each central black hole sits. The same observations picked up the third black hole in the galaxy’s outer region.

A surprise about which black hole is eating fastest

The heaviest of the three, at about 80 million suns, is not the one growing fastest. Its smaller neighbor, at roughly 600,000 suns, is taking in matter at a much higher rate. Its estimated feeding rate is above the maximum predicted by basic models of black hole growth, known as the Eddington limit. According to the release, such rapid growth could offer clues to how some black holes became enormous in the short time available in the early universe.

What it means for understanding the early universe

Astronomers think galaxy collisions were common early on. When galaxies merge, their central black holes can drift together and eventually combine, producing ever larger black holes. The two near the center of J0148-4214 are expected to merge within the next few hundred million years.

Lead author Hannah Übler said the result suggests early-universe processes were efficient at bringing massive black holes together, setting the stage for the mergers that future gravitational wave observatories are expected to detect. Roberto Maiolino of the University of Cambridge, a co-author, said merging may be an additional, fast route to rapid growth.

The outer black hole remains a puzzle. It could be the leftover of an earlier merger that was pushed outward by a gravitational recoil, a kick that can occur when merging black holes emit gravitational waves unevenly. Another possibility, the release says, is that it is slowly moving toward the galaxy’s center.

The work comes from an international team led by MPE. For general readers, the practical takeaway is scientific rather than everyday: the discovery adds a concrete example to the debate over how the biggest black holes formed so soon after the Big Bang.

Around Prague, based on reporting by ScienceDaily