For decades, cosmologists have debated a cosmic version of the chicken-or-the-egg problem: do supermassive black holes form first, with galaxies coalescing around them, or do galaxies grow and then collapse to create black holes at their centres? Now, fresh data from the James Webb Space Telescope (JWST) appears to offer a definitive answer: the black hole wins out.
Every large galaxy in the observable universe hosts a supermassive black hole at its core, and the two are inextricably linked. The galaxy feeds the black hole with gas and dust, while the black hole's energy shapes the galaxy's evolution. But how this symbiotic relationship begins has remained a puzzle. A key difficulty has been the sheer size of these black holes: some reached hundreds of millions of times the mass of the Sun less than 500 million years after the Big Bang — far too quickly for conventional theories of star formation and black hole mergers to explain.
JWST has now spotted galaxies from the very early universe, including distant objects nicknamed 'little red dots', which already contain supermassive black holes. According to astronomers, these black holes appear to have formed before the galaxies that host them. This points to a scenario in which primordial black holes — formed not from stars but from the extreme pressures of the early universe — acted as seeds. These seeds then attracted matter, eventually building the galaxies we see today.
The research, led by scientists analysing JWST data, has not yet been peer-reviewed but has generated significant interest in the cosmology community. The findings suggest that the standard model of galaxy formation may need revision. If confirmed, they would mean that black holes are not just a byproduct of galaxy evolution but a fundamental driver of it.
For the UK public, the implications are profound. Understanding how galaxies and black holes co-evolve helps scientists piece together the history of the cosmos — including the formation of our own Milky Way. It also informs future space missions and telescope projects, many of which involve British researchers and institutions. As JWST continues to peer deeper into the universe's past, we may finally be closing in on one of astronomy's oldest riddles.
Source: New Scientist (based on research presented by Leah Crane)