This is the Most Distant Black Hole Merger Ever Photographed

A deep space image showing various distant galaxies. The left side displays numerous faint celestial objects, with a white square highlighting a specific area. The right side is a zoomed-in view of this highlighted section, featuring a prominent, bright, red galaxy.
The galaxy system ZS7 is seen up close to the right. The James Webb Space Telescope has found evidence of an ongoing merger of two galaxies in the ZS7 system, including their massive black holes. The light detected has been traveling through the cosmos since the Universe was just 740 million years old — a relative baby.

An international team of astronomers using the James Webb Space Telescope (JWST) detected the most distant black hole merger ever observed.

The ongoing galactic merger and their supermassive black holes began when the Universe was only 740 million years old.

One of the black holes has a mass about 50 million times that of the Sun, while the other is “likely similar,” says research team member Roberto Maiolino from the University of Cambridge and University College London in the United Kingdom. However, the mysterious black hole is “harder to measure” because it is embedded in dense, impenetrable gas.

An image from space showing an expansive star field with numerous distant galaxies and bright stars scattered throughout a dark background. Some stars have visible diffraction spikes, creating a starburst effect.
This image shows the environment where ZS7 is. ZS7, relatively small in this image, is surrounded by a large field of hundreds of galaxies.

Given their immense masses, scientists believe these black holes have significantly impacted the evolution of the surrounding galaxies. However, scientists aren’t entirely sure how these objects became so massive in the first place.

“The finding of gargantuan black holes already in place in the first billion years after the Big Bang indicates that such growth must have happened very rapidly, and very early,” the European Space Agency (ESA) explains. “Now, the James Webb Space Telescope is shedding new light on the growth of black holes in the early Universe.”

A composite image of deep space showing three zoom levels of galaxy ZS7. The left panel is a wide shot of numerous galaxies, the middle panel zooms in closer on a section, and the right panel shows a close-up of the distant red galaxy ZS7.
This triptych shows ZS7 in increasing detail. In this image, shot by Webb’s NIRCam instrument, the ionized hydrogen emission in ZS7 is identified by its orange color. Doubly ionized oxygen emission is visible in dark red.

The merger is in system ZS7, and Webb made these groundbreaking observations thanks to its distinctive spectrographic features. Objects so distant, like ZS7, must be viewed from space-based observatories, such as JWST.

“We found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionized gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes,” says research lead author Hannah Übler of the University of Cambridge in the United Kingdom. “Thanks to the unprecedented sharpness of its imaging capabilities, Webb also allowed our team to spatially separate the two black holes.”

“Our findings suggest that merging is an important route through which black holes can rapidly grow, even as cosmic dawn,” Übler continues. With these latest and other observations, scientists are confident that massive black holes have shaped the evolution of the galaxies “from the very beginning [of the Universe].”

When two black holes merge, they generate gravitational waves, or invisible ripples in the very fabric of space-time. While Webb can see these mergers, it is not designed to detect the resulting gravitational waves. Upcoming observatories, like the space-based Laser Interferometer Space Antenna (LISA), are explicitly built for studying gravitational waves.

“Webb’s results are telling us that lighter system detectable by LISA should be far more frequent than previously assumed,” says LISA Lead Project Scientist Nora Luetzgendorf of the ESA in the Netherlands. “It will most likely make us adjust our models for LISA rates in this mass range. This is just the tip of the iceberg.”

The new Webb research results have been published in the Monthly Notices of the Royal Astronomical Society.

Image credits: ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et al.