JWST Reveals a Rapidly Growing 100-Million-Sun Black Hole in the Infant Universe

Using data from the James Webb Space Telescope (JWST), an international team of astronomers has identified a rapidly accreting supermassive black hole at the center of the distant galaxy CANUCS-LRD-z8.6, seen as it was roughly 570 million years after the Big Bang.

CANUCS-LRD-z8.6 belongs to a class of unusually compact, very bright early-universe objects nicknamed "Little Red Dots," a population JWST has revealed since it began observations in 2022. These systems have puzzled researchers because they either appear far too dense for the mass of their stars or seem to host central black holes that are disproportionately massive for such small galaxies.

Analysis of near-infrared spectra from JWST’s Near-Infrared Spectrograph (NIRSpec) — light that has traveled about 13.2 billion years to reach Earth — shows signatures of highly ionized gas concentrated in a compact nuclear region. Those spectral features are the telltale fingerprint of gas being heated and driven by an actively accreting black hole.

From the observed emission the team estimates the central black hole’s mass is on the order of 100 million times the mass of the Sun. While modern supermassive black holes can reach billions of solar masses, a 100-million-solar-mass black hole is exceptionally large for a compact galaxy at this very early epoch, especially one not yet enriched with heavy elements produced by many generations of stars.

By measuring the galaxy’s emitted energy the researchers also estimated its stellar mass and compared it to the black hole mass. The result departs significantly from the familiar correlation seen in the nearby universe: CANUCS-LRD-z8.6’s black hole is far more massive than the galaxy’s stars would predict. This suggests that, in the early universe, black holes may have grown more rapidly than the galaxies that host them.

"This discovery is truly remarkable. We’ve observed a galaxy from less than 600 million years after the Big Bang, and not only is it hosting a supermassive black hole, but the black hole is growing rapidly—far faster than we would expect in such a galaxy at this early time," said team leader Roberta Tripodi (University of Ljubljana).

Team member Maruša Bradač (University of Ljubljana) added that the finding raises important questions about the physical processes that allowed such massive black holes to appear so early in cosmic history. The researchers emphasize that further observations are needed to clarify whether Little Red Dots are unusually dense stellar systems, hosts to overmassive early black holes, or the result of different formation pathways.

The CANUCS collaboration plans continued JWST monitoring of CANUCS-LRD-z8.6 and complementary observations with the Atacama Large Millimetre/submillimetre Array (ALMA). ALMA’s radio-wavelength sensitivity will help map the galaxy’s cold gas and better constrain the environment and growth history of its central black hole.

The team’s results were published on Nov. 19 in Nature Communications.