💫 Early supermassive black holes explained by dark matter

The James Webb Space Telescope (JWST) has uncovered supermassive black holes when the Universe was barely 500 million years old, an early appearance that contradicts classical models predicting a much longer growth time.

These cosmic giants, weighing millions or billions of solar masses, form according to current models through mergers and accretion over timescales of at least one billion years. JWST observations therefore indicate that an accelerated mechanism must have been involved.


A team from the University of California, Riverside proposes a possible origin: the decay of dark matter. This invisible substance, which makes up 85% of the Universe's matter, could release energy by decaying. This energy, even if minuscule, would be enough to heat up the primordial gas clouds.

In a scenario called direct collapse, a gas cloud collapses to form a black hole directly without passing through the stage of a massive star. But this process requires an external energy source to prevent the cloud from fragmenting and allow it to collapse as a single entity. Decaying dark matter could provide this energy.

According to the study, an energy equivalent to one billionth of a billionth of an AA battery per particle is enough to "overcharge" the primordial hydrogen clouds and make direct collapse much more likely.

More concretely, calculations show that dark matter particles with a mass between 24 and 27 electronvolts could trigger this mechanism. These results, published in the Journal of Cosmology and Astroparticle Physics, help reconcile JWST observations with theory.