In his new paper, Professor Jonathan Tan, an astrophysicist at the University of Virginia and the Chalmers University of Technology, proposes that Population III.1 supermassive stars were progenitors of supermassive black holes in the early Universe; high energy photons from the stars ionized the surrounding hydrogen gas far out into the pristine intergalactic medium, eventually engulfing a region that is millions of light-years in size; all supermassive black holes formed in this way leading to flash ionization of all of space and ending the so-called ‘Dark Ages’ of the Universe.
This artist’s impression shows a field of Population III stars as they would have appeared a mere 100 million years after the Big Bang. Image credit: NOIRLab / NSF / AURA / J. da Silva / Spaceengine.
Supermassive black holes lurk in the centers of most large galaxies, including our own Milky Way and are typically millions or even billions of times more massive than the Sun.
Their formation has been much debated, especially as the NASA/ESA/CSA James Webb Space Telescope has been finding many such black holes that exist far away and that have existed as far back in time as the dawn of the Universe.
Known as ‘Pop III.1,’ Professor Tan’s theory proposes that all supermassive black holes form as the remnants of the very first, so-called Population III.1 stars, the very first stars in the Universe which grew to enormous sizes under the influence of energy from a process known as dark matter annihilation, and the theory has predicted many of the Webb’s recent findings.
In his paper, he outlines another prediction of the theory that could shed new light on the origins of the Universe.
“Our model requires that the supermassive star progenitors of the black holes rapidly ionized the hydrogen gas in the Universe, announcing their birth with bright flashes that filled all of space,” Professor Tan said.
“Intriguingly this extra phase of ionization, occurring much earlier than that powered by normal galaxies, may help resolve some recent conundrums and tensions that have arisen in cosmology, including the Hubble Tension, Dynamic Dark Energy and preference for Negative Neutrino Masses, all of which challenge the standard model of the Universe.”
“It’s a connection we didn’t anticipate when developing the Pop III.1 model, but it may prove profoundly important.”
“Professor Tan has developed an elegant model that could explain a two-stage process of stellar birth and ionization in the early Universe,” said University College London’s Professor Richard Ellis, one of the world’s leading observational cosmologists.
“It’s possible the very first stars formed in a brief, brilliant flash, then vanished — meaning what we now see with Webb may be just the second wave. The Universe, it seems, still holds surprises.”
Professor Tan’s paper will be published in the Astrophysical Journal Letters.
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Jonathan C. Tan. 2025. Flash Ionization of the Early Universe by Pop III.1 Supermassive Stars. ApJL, in press; arXiv: 2506.18490
