They are ancient black holes so enormous-and appearing so soon after the universe began-that long‑accepted ideas about how such objects build up mass are starting to unravel. Astronomers are now scrambling to redraw the early history of the cosmos’s most extreme power sources.
How the classic growth story began to fall apart
For a long time, the storyline felt neat. Massive stars reach the end of their lives, their cores cave in, and black holes only a few times the Sun’s mass are left behind. Over vast spans of time, these small black holes collide and merge, while also swallowing gas and dust, eventually ballooning into the supermassive black holes that sit in the centres of galaxies today.
That tidy account is no longer consistent with what telescopes are turning up.
The James Webb Space Telescope (JWST) is uncovering black holes that are already gigantic while the universe is still in its earliest chapter-just a few hundred million years after the Big Bang. With masses ranging from millions to billions of Suns, they seem to arrive far too early for the traditional, gradual “slow growth” pathway to work.
JWST is pushing astronomers towards the conclusion that some of the universe’s largest black holes never went through a long childhood at all.
Warning signs appeared more than two decades ago. Projects such as the Sloan Digital Sky Survey began finding dazzling quasars-objects powered by feeding supermassive black holes-when the universe was only about 800 million years old. Even then, the question was awkward: how could anything become that massive that quickly?
JWST has now shifted the problem earlier still by several hundred million years, making the timing even more difficult to square with the standard picture.
Mystery giants in a newborn cosmos
A particularly striking example is the system known as UHZ1, observed when the universe was roughly 470 million years old. It appears to contain a black hole of around 40 million solar masses.
That would already be startling. What makes UHZ1 especially persuasive is how its glow is distributed across wavelengths. JWST detects its infrared emission, dominated by starlight and warm dust. The Chandra X-ray Observatory measures its X-rays, which are produced as matter spirals inwards and heats up on the way into a central black hole.
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In UHZ1, the infrared and X-ray output line up unusually closely in brightness. That balance points to a black hole whose mass is comparable to-or even exceeds-the combined mass of all the stars in its small host galaxy. That flips the familiar arrangement seen in galaxies like the Milky Way, where the stellar population outweighs the central black hole by a huge margin.
UHZ1 resembles exactly what some theorists anticipated: a black hole that started out large, rather than one that slowly grew.
Direct-collapse black holes and JWST: skipping the stellar stage
This evidence feeds into a leading proposal: direct-collapse black holes. In this scenario, immense clouds of nearly pristine hydrogen and helium in the early universe collapse under gravity in a single catastrophic event, producing black holes of roughly 1,000 to 1,000,000 solar masses right from birth.
Those hefty “seed” black holes can then keep growing-pulling in surrounding gas and merging with other black holes-reaching supermassive sizes far faster than black holes formed from dead stars are expected to manage.
Theorists also laid out what JWST should see if direct collapse really happens: sources that are extremely compact, extraordinarily bright relative to any surrounding galaxy, and showing characteristic infrared colours. UHZ1 appears to match those expectations, strengthening the case that direct collapse occurred in at least some early environments.
A related difficulty for the slow-growth model is that black holes cannot simply eat at any rate they like. As the infalling material heats up, it radiates strongly; that radiation pushes back on the incoming gas. This so‑called Eddington-limited behaviour caps how quickly a black hole can gain mass under typical conditions. To reach tens of millions of solar masses in only a few hundred million years, many objects would need either unusually massive starting seeds, long periods of near‑continuous feeding, or episodes of accretion that break the usual limits.
The puzzle of the “little red dots”
UHZ1 is not a one-off oddity. Since JWST began routine science observations, astronomers have identified a group of small, reddish, very distant sources in multiple deep programmes, including CEERS, JADES and NGDEEP.
These objects quickly earned a label: the “little red dots”. At first, many teams interpreted them as implausibly massive early galaxies-so dense they seemed capable of putting pressure on standard cosmological models. As more observations arrived, a different interpretation gained ground.
A large fraction of little red dots look less like oversized galaxies and more like exposed, overgrown black holes.
Consider QSO1, observed when the universe was only about 700 million years old. Astronomers can estimate its mass by examining how quickly gas orbits the centre. The measured speeds imply a black hole of roughly 50 million solar masses.
The twist comes when researchers search for the surrounding host galaxy. There is scarcely any evidence for a substantial stellar population.
QSO1 therefore looks like a massive black hole accompanied by only a tiny galaxy-or perhaps almost no galaxy at all. It is precisely the sort of configuration that used to live mostly in theoretical papers, until JWST began revealing real candidates.
A possible new cosmic creature: the quasi-star
Another JWST target, nicknamed “The Cliff”, may point to a different-and even more peculiar-growth stage. It appears to have a mass of billions of solar masses and is seen about 1.8 billion years after the Big Bang.
JWST instruments detect a sudden change in its brightness at a specific wavelength, a feature associated with extremely dense hydrogen gas. That pattern resembles predictions for a “black hole star”, more commonly called a quasi-star.
A quasi-star is not a normal star: it is a black hole surrounded by an inflated, luminous envelope of gas.
In this model, a direct-collapse black hole forms inside an enormous gas cloud. As the black hole feeds rapidly, the energy it releases swells the surrounding gas into a vast, star‑like shroud. From far away it could look like a single outsized star, but its true engine would be a black hole hidden inside a gaseous cocoon.
Were some black holes born before galaxies?
Direct collapse is not the only contender. A more radical possibility reaches even further back-towards the earliest moments after the Big Bang itself.
In the 1970s, Stephen Hawking proposed that exceptionally dense patches in the young universe might have collapsed directly into primordial black holes. Unlike black holes created by dying stars, these would form from raw density fluctuations in the early cosmos and could, in principle, span a wide range of masses.
If some primordial black holes were sufficiently massive-and if they merged frequently enough-they might provide the seeds for the “monsters” JWST is now uncovering. One study argues that this could explain the galaxy GN-z11, seen just 400 million years after the Big Bang and already hosting a black hole of around one million solar masses.
Between these ideas sits a compromise option: “not-quite-primordial” black holes. Here, dense gas clumps collapse within the first few million years-before stars ignite-but not as early as Hawking’s original primordial mechanism. These objects would overlap with direct-collapse black holes, though the required conditions would be somewhat different.
What chemical fingerprints reveal
Chemistry provides a valuable clue. Elements heavier than hydrogen and helium-such as carbon, oxygen and iron-are mostly created inside stars and then dispersed by supernova explosions.
Many of the most distant galaxies and black holes JWST observes show very low abundances of these heavy elements. That implies their gas has undergone little recycling through earlier generations of stars.
This near‑pristine chemical signature suggests some early black holes formed before many stars had time to form, live and explode.
That evidence fits naturally with pictures in which black holes emerge directly from primordial, or almost primordial, gas rather than from the remnants of massive stars.
A mixed family of supermassive black holes
Most researchers doubt there is a single elegant mechanism that explains every supermassive black hole. Instead, several pathways probably operated in parallel, with different routes dominating in different places and at different times.
- Direct-collapse black holes: vast gas clouds collapsing straight into massive black holes
- Primordial or early-universe black holes: formed from density fluctuations soon after the Big Bang
- Stellar-collapse black holes: initially small remnants of massive stars, later growing through accretion and mergers
Forthcoming surveys should help quantify how much each channel contributes. The European Space Agency’s Euclid mission, launched in 2023, is mapping huge swathes of the sky to identify more distant candidates. NASA’s Nancy Grace Roman Space Telescope, expected to launch in 2027, will add wide‑field infrared capability that complements JWST’s deeper, narrower view.
Working alongside JWST, these facilities should uncover thousands more early black holes, enabling astronomers to measure how frequently each origin route occurs.
Another complementary approach will come from gravitational-wave astronomy. As black holes merge, they ripple space-time; future detectors-especially those designed to listen for lower-frequency waves from massive mergers-should help distinguish whether the earliest supermassive black holes grew mainly by repeated mergers, rapid gas feeding, or a blend of both.
Why these early black holes change our view of the universe
Supermassive black holes are not merely quiet occupants of galactic centres. When they feed, they can blaze intensely and launch jets that heat surrounding gas or drive it outwards, either suppressing star formation or, in some circumstances, triggering it. Their influence can reshape matter on scales far beyond the central region.
If some black holes formed very early and already very massive, they may have helped steer how the first galaxies and galaxy clusters assembled. That would also affect how the universe shifted from an early, dark, neutral fog to the clearer, star‑filled cosmos we observe later on.
To rewrite how black holes began is to rewrite a significant part of cosmic history.
Key terms readers often ask about
Black hole: A region where gravity is so strong that nothing-not even light-can escape after crossing the boundary known as the event horizon.
Quasar: A galaxy whose central supermassive black hole is actively accreting, creating an intensely bright disc of hot gas and powerful radiation.
Redshift: A measure of how much the universe has stretched the light from a distant object; a higher redshift means we are seeing further back in time.
How simulations put these ideas on trial
To test whether these formation routes are viable, astrophysicists build enormous computer simulations. These models follow dark matter, gas, radiation and gravity across billions of light‑years, starting from conditions shortly after the Big Bang.
By adjusting how gas cools, collapses and fragments-and by inserting different prescriptions for black hole formation-researchers create “mock” universes. They then compare the resulting black hole populations with what JWST and other observatories actually detect.
If a simulation that includes direct-collapse black holes, for instance, naturally produces UHZ1‑like systems in the correct numbers and at the right cosmic times, confidence in that mechanism increases. If it does not, the assumptions must be refined-or new physics and new scenarios may be required.
As the combined datasets from JWST, Euclid and, later, Nancy Grace Roman Space Telescope grow, these simulations will face far stricter tests. Many astronomers expect further surprises-and perhaps more apparent “universe breakers”-to emerge from the data.
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