CosmosIn60CosmosIn60
The James Webb Space Telescope is finding black holes in the early universe so massive they outweigh their entire host galaxies — and nobody fully knows how.
When astronomers peer at the earliest galaxies in the universe, they expect to find black holes — small ones, young ones, still in the early stages of growth. What the James Webb Space Telescope is actually finding is something far more unsettling: black holes so enormous they sometimes rival, or even outweigh, the entire stellar population of the galaxies around them. In nearby, mature galaxies like the Milky Way, a central black hole typically accounts for roughly 0.1% of the galaxy's total stellar mass. In some of the distant, young galaxies JWST is now resolving, that ratio flips to as much as 40% — or higher. The universe apparently did not follow the rulebook astronomers wrote for it.
For decades, the relationship between supermassive black holes and their host galaxies appeared to be one of the most reliable patterns in all of cosmology. Study enough local galaxies and you find the same ratio again and again: the central black hole mass is roughly 0.1% of the galaxy's total stellar mass. The two components — the black hole and the surrounding stars — seem to co-evolve, growing together over billions of years in a kind of gravitational partnership.
That pattern gave astronomers a working model: galaxies build stars, supernovae leave behind stellar remnants, some of those remnants merge and grow into massive black holes over cosmic timescales. The black hole stays proportional because the same gas supply that feeds star formation also feeds the black hole. Feedback processes — jets and radiation from the black hole blasting gas back out of the galaxy — then shut down both star formation and black hole growth simultaneously, locking in that 0.1% ratio.
JWST changed the picture entirely. Launched in December 2021 and fully operational since 2022, the telescope's infrared sensitivity lets it peer back to within a few hundred million years of the Big Bang. What it found in those primordial galaxies was a mass ratio that looked nothing like the local universe, raising a fundamental question: did galaxies in the early cosmos grow their black holes first, and their stars second?
The numbers from JWST's earliest systematic surveys were striking. Research led by astronomers at Harvard's Center for Astrophysics and the University of Arizona, published in The Astrophysical Journal Letters in January 2024, examined galaxies as they existed 12 to 13 billion years ago. The black holes at their centers were 10 to 100 times more massive than the standard scaling relation would predict for galaxies of that size.
To put that into everyday terms: imagine finding a human heart that weighed as much as the entire body it was pumping blood through. The ratio is that extreme. In the most dramatic cases, the mass difference between the black hole and the galaxy's stars dropped from the expected 1,000-to-1 all the way to 1-to-1. The black hole and the galaxy were, in effect, equally massive.
The study's authors were careful about language. These objects were not merely "large" black holes — the astrophysics community now uses the term overmassive to describe black holes that violate the established mass scaling relation. That word choice matters: it acknowledges that something genuinely anomalous is happening, not just a statistical outlier or a measurement artifact.
What makes this finding especially hard to dismiss is the scale of the sample. JWST did not find one or two unusual galaxies. Overmassive black holes appear to be common in the early universe, showing up across multiple independent surveys and research teams. The anomaly is systematic, not incidental.
One of the most striking individual cases came from an international team led by the University of Cambridge, using data from JWST's JADES survey published in Nature in December 2024. They identified a black hole that existed just 800 million years after the Big Bang — ancient even by cosmic standards — with a mass of approximately 400 million times the mass of our Sun.
That alone would be remarkable. What makes it extraordinary is the mass ratio: this single black hole accounts for roughly 40% of the total mass of its host galaxy. In contrast, the Milky Way's central black hole, Sagittarius A*, weighs in at about 4 million solar masses — approximately 0.001% of the galaxy's stellar mass. The Cambridge team's discovery outweighs its galaxy's stars by a factor that has no parallel in the modern universe.
There was a further twist: this particular black hole was dormant. It was accreting gas at only about 2% of its theoretical maximum rate — essentially taking a nap after a period of intense feeding. Computer simulations suggest that black holes operate in cycles, eating for 5 to 10 million years, then going quiet for roughly 100 million years. This object was caught in one of those long rest periods, which itself tells a story: it must have grown to 400 million solar masses during earlier, more violent episodes of consumption.
If the dormant giant represents a black hole caught resting, LID-568 represents the opposite extreme. Discovered using JWST in combination with NASA's Chandra X-ray Observatory and announced by NSF NOIRLab researchers in November 2024, LID-568 is a black hole observed at approximately 1.5 billion years after the Big Bang, eating matter at more than 4,000% of the Eddington limit.
The Eddington limit is the theoretical cap on how fast a black hole can accrete — the point where the outward radiation pressure from infalling material equals the inward pull of gravity, shutting off further feeding. Most black holes in the modern universe operate at or below this limit. LID-568 blows past it by a factor of 40.
This process — super-Eddington accretion — was theorized for decades but rarely observed with such clarity. At this rate, a black hole can pack millions of years of growth into a relatively short burst. LID-568's mass is 7.2 million times the mass of the Sun, which sounds large until you consider that it reached that size in roughly the first billion years of cosmic history. The JWST spectrograph also detected powerful outflows — gas being expelled at velocities of 500 to 600 km/s — suggesting LID-568's feasting is not quiet or gradual, but explosive.
The significance here extends beyond one exotic object. If black holes in the early universe routinely underwent super-Eddington phases, it explains how they grew so disproportionately large while their host galaxies were still assembling stars at a slower pace.
For a time, researchers might have argued that overmassive black holes were a feature of large, unusual early galaxies — perhaps gravitationally dense environments that accelerated growth in unusual ways. A 2026 preprint using JWST data demolished that argument. The study, led by Eduardo Iani of the Institute of Science and Technology Austria, identified two dwarf galaxies — named Pelias and Neleus — at redshifts of approximately 0.71 and 0.75 (roughly 7 billion years ago), each hosting black holes with masses up to 60% of the galaxy's total mass.
Dwarf galaxies are among the smallest, least massive galaxies known. Their stellar masses sit around 10 million solar masses — a tiny fraction of the Milky Way's roughly 60 billion solar masses. Finding a black hole that constitutes more than half the mass of a dwarf galaxy stretches even the most flexible theoretical models. The typical mass ratio in the local universe for galaxies of this size would place the black hole at well below 1% of the stellar mass. Pelias and Neleus come in at 600 times that proportion.
These discoveries are important because dwarf galaxies are the most common galaxy type in the universe and are considered the building blocks of larger structures. If overmassive black holes are lurking in them at cosmological distances, the problem is far more widespread than early JWST data suggested.
Astrophysicists are not short of ideas to explain overmassive black holes — they are short of ways to choose between them.
The heavy seed hypothesis proposes that the first black holes were born large, not small. Instead of forming from the collapsed cores of individual massive stars (which produce black holes of roughly 10–100 solar masses), heavy seeds are thought to form from the direct collapse of entire primordial gas clouds into black holes of 100,000 solar masses or more. Starting from a larger seed, reaching billions of solar masses within the first billion years becomes plausible without requiring physics that breaks known limits.
The super-Eddington accretion hypothesis does not require a special seed. Instead, it argues that the dense, gas-rich environments of the early universe allowed even small black holes to feed far above their Eddington limits in short, intense bursts — as LID-568 demonstrates. The simulations backing this model show that such episodes, spread over the first billion years, are sufficient to produce the overmassive objects JWST is observing.
The "little red dots" enigma adds another layer. JWST has catalogued hundreds of compact, red objects in the high-redshift universe that appear to be simultaneously star-dense and black-hole-dominated. A 2025 Nature paper proposed that these objects are young supermassive black holes embedded in dense ionized gas cocoons, where spectral line broadening comes from electron scattering rather than gas motion — which would mean astronomers have been misreading their masses. If correct, some apparent overmassive black holes may be even more extreme than current estimates suggest.
None of these explanations has won the debate. The evidence currently favors a combination: some black holes began as heavy seeds, others grew through super-Eddington bursts, and the dense, turbulent conditions of the early universe simply allowed both pathways to operate more freely than they can today.
The overmassive black hole problem is not a minor asterisk in cosmology — it is a direct challenge to the standard model of how galaxies and black holes co-evolve. If the co-evolution model is correct, the 0.1% mass ratio should hold at all cosmic epochs. It does not. JWST has made that undeniable.
What replaces the co-evolution model matters enormously for understanding the universe we live in now. The Milky Way's own central black hole, Sagittarius A*, is 4 million solar masses. The galaxy it anchors contains hundreds of billions of stars. If the Milky Way underwent an early phase where the black hole was proportionally as massive as those JWST is finding, then the galaxy's entire subsequent growth in stars was, in some sense, built around a pre-existing gravitational anchor. The black hole came first; the galaxy caught up later.
That sequence inverts the story astronomers told for decades — and it has implications for why galaxies look the way they do. Feedback from overmassive early black holes may have shaped the temperature, density, and star-forming potential of the surrounding gas across billion-light-year scales. In other words, the black holes that formed first may have set the initial conditions for everything that came after, including the formation of the solar system.
JWST's operational lifespan is expected to extend through at least the mid-2030s. Each year of data pushes the survey of early black holes deeper in both time and sample size. Upcoming results from the JADES and COSMOS-Web surveys are likely to either confirm that overmassive black holes are universal in the early universe or reveal the rare conditions that produce them — and either answer will force a rewrite of textbooks.
JWST is finding black holes in early galaxies that are 10 to 100 times more massive than the scaling relation established in the local universe would predict. In the most extreme cases, the black hole's mass equals that of all the stars in its host galaxy combined — a ratio roughly 1,000 times higher than what is typical in the present-day universe.
The Eddington limit is the theoretical maximum rate at which a black hole can pull in gas before radiation pressure pushes the gas back out. Super-Eddington accretion means the black hole is feeding above that limit. Black hole LID-568 was observed accreting at more than 4,000% of the Eddington limit — consuming matter at 40 times the theoretical cap — which is one mechanism that could explain how black holes grew so massive so early.
The JWST data increasingly suggests that in at least some cases, yes — black holes grew faster than their host galaxies in the earliest epochs of cosmic history. A dormant black hole found 800 million years after the Big Bang already weighed 400 million solar masses and constituted 40% of its galaxy's mass, implying the black hole grew to that size before the surrounding stellar population fully assembled.
Little red dots are compact, faint red objects appearing in large numbers in JWST's deep-field images of the early universe. Research published in Nature in 2025 suggests they are young supermassive black holes wrapped in dense cocoons of ionized gas. They matter because they may represent a previously unrecognized population of black holes in the act of rapid early growth — adding to the evidence that overmassive black holes were common, not exceptional, in the first two billion years.
Not necessarily — but it raises the question. Current data suggests overmassive black holes are more common at high redshifts (early times) and that the proportion normalizes as galaxies age and grow more stars. Whether the Milky Way passed through such a phase billions of years ago is an open research question. What is clear is that the local 0.1% ratio is not a cosmic law, but rather the endpoint of a long evolutionary process that began very differently.
JWST is not just finding black holes that are large — it is finding black holes that redefine what the word "large" means when applied to the early universe. The steady accumulation of overmassive black holes across multiple surveys, galaxy types, and cosmic epochs suggests this is a feature of how the universe assembled itself, not a handful of bizarre exceptions. The next phase of JWST observations, combined with data from future missions like NASA's Nancy Grace Roman Space Telescope, will push these measurements to even earlier epochs — within the first 300 million years after the Big Bang. Whatever is found there will either deepen the mystery or, finally, point toward the explanation that cosmology has been searching for since the first JWST deep field dropped in 2022.
NASA's James Webb Space Telescope captured the sharpest image ever taken around a black hole, revealing that 87% of the hot dust near the Circinus Galaxy's core is being consumed — not blown away.
A supergiant in Andromeda dimmed 10,000-fold and disappeared with no supernova. The numbers behind this 'failed supernova' point to a black hole born in silence.
