The James Webb Space Telescope has spotted tiny, unnaturally bright red objects in the early universe. Their light outshines by a hundredfold what you’d expect from ordinary galaxies of that era. Inside, they likely hide black holes with the mass of billions of suns — except there wouldn’t be enough time for them to grow gradually since the Big Bang.
A new study offers a solution: these black holes didn’t grow: they were born giants. They emerged from dark matter — the invisible stuff that permeates the cosmos. In the early universe, a phase transition occurred, much like a pot of cooling jelly: almost all the matter instantly solidified, but here and there liquid pockets remained. These rare bubbles collapsed under their own gravity, forming supermassive black holes without the need for slow growth.
The same process would have generated gravitational waves, ripples in spacetime, of ultra-low frequency. Each such wave is longer than our entire galaxy and squeezes and stretches the Earth by a fraction of a proton. We could detect them by watching pulsars: these dead stars spin with the precision of atomic clocks, and the slightest hiccup in their rhythm would betray a passing gravitational wave. If the signal is found, the hypothesis gets undeniable proof.
as written by the authors arXiv:2604.01304
JWST has revealed an abundant population of compact, low-metallicity "Little Red Dots" (LRDs) at high redshift, challenging conventional scenarios in which supermassive black holes (SMBHs) grow from stellar-mass seeds. We consider a scenario in which the SMBHs are instead supermassive primordial black holes (SMPBHs), formed directly in a decoupled, subdominant dark sector undergoing a first-order phase transition. Unlike conventional stochastic phase transitions, our mechanism is based on the catalysis by domain walls (DWs): most of the Universe completes the transition rapidly, while rare long-lived false-vacuum domains survive because of DW statistics and collapse into PBHs. This mechanism naturally yields SMPBH seeds with masses up to $$M_{\rm PBH}\sim \mathcal{O}(10^{10}) M_\odot$$, whose abundance can account for the observed LRD population. It also avoids the usual tensions with phase transition completion, $$\Delta N_{\rm eff}$$, and large curvature perturbations. The dark phase transition simultaneously generates an ultra-low-frequency stochastic gravitational-wave background peaking near the pulsar-timing-array range, providing a test of this dark-sector origin of LRDs.
According to the authors’ calculations, the primordial black holes in the red dots could reach ten billion solar masses — almost as much as the entire Milky Way galaxy!