JWST red dots reveal rapidly growing early black holes

by Robert Schreiber
Berlin, Germany (SPX) Jan 15, 2026

Since the James Webb Space Telescope began science operations in December 2021 some 1.5 million kilometres from Earth, astronomers have been puzzled by compact, intensely red sources scattered through its deep images of the early universe. These so called little red dots appear when the universe is only several hundred million years old, then seem to vanish about a billion years later, prompting debate over whether they represented unexpectedly massive early galaxies or some other phenomenon.

A team at the University of Copenhagen's Cosmic Dawn Center now reports that the mystery objects are young, rapidly growing black holes embedded in dense cocoons of gas. Using two years of continuous analysis of JWST observations, the researchers conclude that the red colour arises as radiation from the hot gas near the black holes is filtered through and reprocessed by surrounding ionized material, revealing some of the most violent forces in the cosmos in their infancy.

"The little red dots are young black holes, a hundred times less massive than previously believed, enshrouded in a cocoon of gas, which they are consuming in order to grow larger. This process generates enormous heat, which shines through the cocoon. This radiation through the cocoon is what gives little red dots their unique red colour," says Professor Darach Watson of the Niels Bohr Institute's Cosmic Dawn Center, one of the principal researchers on the study. He adds that the revised interpretation removes the need to invoke completely new types of events to explain the observations.

There are now hundreds of known little red dots in JWST data, all now interpreted as young black holes in a rapid growth phase. Although described as some of the smallest supermassive black holes yet identified, they can still reach up to roughly 10 million times the mass of the Sun, with corresponding diameters of around 10 million kilometres.

As gas falls toward one of these black holes, it spirals into a compact accretion structure that the team likens to a disk or funnel. The gas accelerates to very high speeds and is compressed to such extreme densities that it heats to temperatures of millions of degrees, producing intense radiation that can outshine entire galaxies and making accretion onto black holes the most energetic process known.

However, only a small fraction of the inflowing material ultimately crosses the event horizon. "When gas falls towards a black hole, it spirals down into a kind of disk or funnel towards surface of the black hole. It ends up going so fast and is squeezed so densely that it generates temperatures of millions of degrees and lights up brightly. But only a very small amount of the gas is swallowed by the black hole. Most of it is blown back out from the poles as the black hole rotates. That's why we call black holes 'messy eaters'," explains Watson.

The new interpretation also helps address a broader cosmological puzzle: the surprisingly rapid appearance of extremely massive black holes in the early universe. Observations show that by about 700 million years after the Big Bang, some galaxies already host central black holes with masses approaching a billion Suns, raising questions about how they could have grown so fast.

According to the Copenhagen team, the dense gaseous cocoons around little red dots provide exactly the kind of fuel supply needed to power an early growth spurt. "We have captured the young black holes in the middle of their growth spurt at a stage that we have not observed before. The dense cocoon of gas around them provides the fuel they need to grow very quickly," says Watson. The objects therefore offer a direct view of an evolutionary phase that likely precedes the emergence of the supermassive black holes seen in mature galaxies such as the Milky Way.

Today, a supermassive black hole about four million times the mass of the Sun anchors the centre of the Milky Way, and comparable or larger black holes appear to reside in the cores of most galaxies. Yet their detailed formation pathways and early evolution remain uncertain. By tying the little red dots to young supermassive black holes in dense ionized environments, the new work links JWST's high redshift discoveries to this long standing question.

The study, which has secured the front cover of the journal Nature, is authored by V. Rusakov, Darach Watson, G. P. Nikopoulos, Gabriel Brammer, R. Gottumukkala, T. Harvey, Kasper Elm Heintz, R. Damgaard, S. A. Sim, Albert Sneppen, A. P. Vijayan, N. Adams, D. Austin, C. J. Conselice, C. M. Goolsby, Sune Toft and J. Witstok. The paper is titled "Little red dots as young supermassive black holes in dense ionized cocoons (N&V)."

Research Report:Little red dots as young supermassive black holes in dense ionized cocoons (N&V)