Three JWST Clues to How Early Black Holes Grew So Fast

JWST has revealed compact, red early-universe sources known as little red dots (LRDs), some of which may be associated with rapidly accreting massive black holes. Their abundance and apparent black-hole growth rates are difficult to reconcile with a simple picture in which every black hole begins as the remnant of an ordinary star and grows steadily thereafter.

Three recent lines of work point to a more flexible answer: black holes may have begun with larger seeds, gained mass through interactions and mergers, and sometimes been hidden inside dense gas rather than appearing as conventional quasars. These are complementary hypotheses, not a single settled solution.

1. Early dark-matter halos could create heavier seeds

The “not-quite-primordial” black-hole proposal sits between two familiar ideas. It does not require density fluctuations large enough to form primordial black holes immediately after inflation. Instead, more modest enhanced fluctuations could cause dark-matter halos to collapse exceptionally early. 33

For halos that form before roughly redshift 200, the cosmic microwave background would suppress molecular-hydrogen formation. Without that cooling pathway, infalling gas may avoid the usual fragmentation into stars and instead undergo direct collapse into a black hole. 33

The appeal is straightforward: if some black holes begin before normal star formation in their host halos, they may start out earlier and potentially more massive than stellar-remnant seeds. That reduces, rather than eliminates, the amount of extreme later growth needed to explain massive early black holes.

This remains a theoretical mechanism. Its relevance to the observed LRD population depends on how often these rare early conditions occurred and whether their predicted descendants match JWST observations.

2. Close LRD pairs could reveal a merger channel

A separate JWST image-analysis study found four candidate pairs in which two LRDs lie unusually close together in the universe about 12.5 to 12.8 billion years ago. Spectroscopy for two pairs found nearly identical redshifts for the members, supporting the conclusion that they were physically near one another rather than simply aligned along the line of sight. 15

If LRDs trace actively growing black holes, close galaxy encounters can matter in two ways:

• Gas inflow: gravitational interactions can channel gas toward galactic centers, supplying fuel for accretion.
• Eventual coalescence: as host galaxies merge, their central black holes may form binaries and ultimately merge, adding mass directly.

That interpretation is promising but not yet a direct observation of black-hole mergers. The sources are candidate LRD pairs, and determining whether both members contain massive accreting black holes—and whether they will merge—requires more spectroscopy, dynamical constraints, and ultimately gravitational-wave evidence. The current observation is best viewed as evidence that close environments may have been important during this early growth era. 15

3. A “black hole star” could hide rapid growth inside gas

MoM-BH*-1 offers a different clue: not how a black hole begins or joins another, but how it could grow while looking unlike a standard active galactic nucleus.

The proposed interpretation is an accreting black hole embedded in a dense hydrogen envelope. MoM-BH*-1 is observed at redshift 7.7569, when the universe was about 660 million years old; the modeled envelope spans roughly 10 to 100 astronomical units, a solar-system-like scale. 2326

In this picture, energy released by matter falling toward the black hole is absorbed, scattered, and re-emitted by the surrounding gas. The result can have a star-like spectrum even though the underlying power source is accretion. The model associates the source with a central black hole of roughly 100,000 solar masses and a luminosity on the order of 80 to 100 billion Suns. 2426

That matters for LRDs because dense gas can both feed a black hole and reshape the light astronomers observe. A population of gas-shrouded accretors could therefore look compact and red while undergoing intense growth. But MoM-BH*-1 is an exceptional object and a modeled interpretation; it does not establish that all LRDs are black-hole stars.

A multi-stage explanation, not a single fix

Taken together, the three ideas describe a plausible growth sequence:

1. Start early and heavy: direct collapse in unusually early halos could create seeds before ordinary stars form.
2. Feed efficiently: dense gas envelopes could conceal bright, rapid accretion.
3. Build through assembly: galaxy interactions and black-hole mergers could add mass and trigger further feeding.

The key uncertainty is population-wide relevance. LRDs are not necessarily one uniform class, and the available evidence ranges from theory to candidate pairs to interpretation of an individual unusual source. Still, the combined picture moves the question beyond a single improbable growth path: the first massive black holes may have had multiple ways to form, feed, and merge in the young universe.