Over its first three years, Webb's surveys of the early Universe have turned up an increasing number of small, extremely distant, and strikingly red objects. These so-called Little Red Dots (LRDs) remain a tantalising mystery to astronomers, despite their unexpected abundance. The discovery in CANUCS-LRD-z8.6, made possible by Webb’s exceptional capabilities, has assisted in this hunt for answers. Webb’s Near-Infrared Spectrograph (NIRSpec) enabled researchers to observe the faint light from this distant galaxy and detect key spectral features that point to the presence of an accreting black hole.

Roberta Tripodi, lead author of the study and a researcher of the University of Ljubljana FMF, in Slovenia and INAF - Osservatorio Astronomico di Roma, in Italy, explained: "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. This challenges our understanding of black hole and galaxy formation in the early Universe and opens up new avenues of research into how these objects came to be."

The team analysed the galaxy's spectrum, which showed gas which had been highly ionised by energetic radiation, and suggested it was rotating quickly around a central source. These features are key characteristics of an accreting supermassive black hole. The precise spectral data yielded an estimate of the black hole’s mass, revealing it to be unusually large for such an early stage in the Universe, and showed that CANUCS-LRD-z8.6 is compact and has not yet produced many heavy elements – a galaxy at an early stage of its evolution. This combination makes it an intriguing subject for study.

Additionally, the Webb spectroscopy allowed the team to measure how much energy is emitted at different wavelengths, from which they were able to characterise the galaxy’s physical properties. This allowed them to determine the mass of the galaxy’s stars and compare it with the black hole’s mass. "The data we received from Webb was absolutely crucial,” added Dr. Nicholas Martis, a collaborator from the University of Ljubljana, FMF, who helped analyse the spectrum of the source. “The spectral features revealed by Webb provided clear signs of an accreting black hole at the centre of the galaxy, something that could not have been observed with previous technology. What makes this even more compelling is that the galaxy’s black hole is overmassive compared to its stellar mass. This suggests that black holes in the early Universe may have grown much faster than the galaxies that host them."

Astronomers have previously observed that the mass of a supermassive black hole and its host galaxy are linked: the larger a galaxy grows, the larger its central black hole also becomes. CANUCS-LRD-z8.6 is the most massive host galaxy known at such an early time, yet its central black hole is even more massive than we would expect, defying the usual relation. The result suggests that black holes may have formed and started growing at an accelerated pace in the early Universe, even in relatively small galaxies.