The universe does not manufacture black holes through a single dominant process.
For years, three gravitational-wave detectors have been listening to the universe's most violent collisions, and in nearly 400 confirmed events, they have heard something profound: the cosmos does not build black holes by a single method, but through many. The LIGO-Virgo-KAGRA collaboration's latest catalogue reveals stellar collapse, dense cluster encounters, and generational chains of mergers all at work simultaneously — a plurality of cosmic architectures rather than a single blueprint. What began as the detection of individual anomalies has matured into the reading of a population, and in that population, the universe's deeper logic is beginning to surface.
- Nearly 400 gravitational-wave detections have shattered the assumption that black holes form through one dominant process, forcing a fundamental rethinking of stellar and cosmic evolution.
- Some detected black holes spin thousands of times per second — inheriting angular momentum from previous collisions — pointing to multi-generational merger chains that stretch back through cosmic time.
- Standout events like GW241127, with wildly mismatched masses and visibly wobbling orbits, and GW240615, pinpointed with unprecedented sky precision, are pushing theoretical models past their limits.
- Two distinct mass populations of rapidly spinning black holes — one between 10 and 20 solar masses, another above 45 — suggest different formation channels operating in parallel across the universe.
- The field has crossed a threshold: with enough detections to do population-level statistics, researchers can now ask not just whether black holes merge, but how, why, and what their histories reveal about the cosmos.
Three gravitational-wave detectors — two in the United States, one in Italy — have been recording the universe's collisions for years, and the picture they've assembled has changed everything. The LIGO-Virgo-KAGRA collaboration's updated catalogue, GWTC-5.0, contains nearly 400 confirmed detections of black holes and neutron stars merging, and the volume of data has revealed something unexpected: the universe manufactures black holes through multiple distinct processes, not one.
Sharan Banagiri of Monash University, who led the analysis, described three apparent formation channels. Some binary black holes arise when massive gas clouds collapse into enormous stars that eventually die as black holes. Others form in dense stellar clusters, where black holes drift through crowded stellar neighborhoods and collide by chance. A third population appears to be the product of previous mergers — black holes born from earlier collisions that go on to collide again, creating a genealogy of mergers across cosmic generations.
The catalogue includes events that strain existing theory. GW241127 features black holes of dramatically different masses in orbits so tilted by spin that they visibly wobble as they spiral inward. GW240615 has been localized in the sky with unprecedented precision. These are not marginal findings — they are the kind of observations that force theorists to revise their models.
The spin rates are among the most striking results. When two black holes merge, the resulting object inherits the angular momentum of both, spinning faster than either parent — in some cases, thousands of rotations per second. Rapidly spinning black holes cluster into two distinct mass ranges, between 10 and 20 solar masses and above 45, hinting at different formation histories.
Sylvia Biscoveanu of Princeton called GWTC-5 a threshold moment: the field has moved from celebrating individual detections to reading population-level patterns. With nearly 400 events, researchers can now distinguish between formation channels and begin to understand not just that black holes merge, but how and why. The multiple pathways are not a complication in the data — they are the actual architecture of how the cosmos builds itself.
Three gravitational-wave detectors—two in the United States and one in Italy—have been listening to the universe collide for years now, and what they've heard has fundamentally changed how scientists understand where black holes come from. The LIGO-Virgo-KAGRA collaboration released an updated catalogue this year containing nearly 400 confirmed detections of black holes and neutron stars crashing into one another, and the sheer volume of observations has revealed something unexpected: the universe does not manufacture black holes through a single, dominant process. Instead, it appears to have multiple recipes.
Sharan Banagiri, a research fellow at Monash University who led the analysis of the new Gravitational-Wave Transient Catalog (GWTC-5.0), described the findings with the precision of someone who has spent months staring at patterns in data. Some binary black holes, he explained, likely form when a massive cloud of gas collapses into two enormous stars that eventually become black holes. Others appear to originate in dense stellar clusters, where black holes wander through crowded neighborhoods of stars and occasionally collide. A third population seems to be the product of previous mergers—black holes born from the collision of two other black holes, which then go on to collide again. This hierarchical pathway, repeated across cosmic time, creates a genealogy of mergers stretching back through generations.
The catalogue's expansion is the largest single increase in gravitational-wave observations to date, and it includes events with properties that push against what researchers thought was possible. One detection, labeled GW241127, contains black holes of dramatically different masses locked in orbits so tilted by their spins that they visibly wobble as they spiral together. Another event, GW240615, has been localized to a region of sky with unprecedented precision. These are not marginal discoveries—they are the kind of observations that force theorists to reconsider their models.
Perhaps the most striking finding concerns the spin rates of these black holes. The sun rotates once every 25 days. If it were compressed into a black hole and spun at the rates observed in this catalogue, it would rotate thousands of times per second. The physics required to spin black holes to such extremes points back to those hierarchical mergers. When two black holes collide, the resulting object inherits the angular momentum of both progenitors, spinning faster than either parent. The researchers found that rapidly spinning black holes cluster into two distinct mass ranges—one between 10 and 20 times the sun's mass, and another above 45 solar masses—suggesting different formation channels at work.
Sylvia Biscoveanu, an assistant professor at Princeton and co-author of the study, emphasized that GWTC-5 represents a threshold moment in gravitational-wave astronomy. The field is transitioning from the era of individual discoveries—each detection a remarkable anomaly—to the era of population statistics. When you have nearly 400 events, you can ask questions that a handful of observations could never answer. You can see patterns. You can distinguish between populations. You can begin to understand not just that black holes merge, but how and why they merge, and what that tells us about the universe's history.
Eric Thrane, a chief investigator at the ARC Centre of Excellence for Gravitational Wave Discovery, captured the shift in perspective with a single image: the field is no longer studying individual anomalies but observing a true kaleidoscope of cosmic collisions. The black holes in this catalogue are more massive than those detected even a few years ago, spinning faster, and exhibiting properties that challenge existing astrophysical models. As the detectors continue to operate and the catalogue grows, the universe's methods for creating black holes will become clearer—not simpler, but clearer. The multiple pathways are not a complication; they are the actual architecture of how the cosmos works.
Notable Quotes
Binary black hole mergers form in several different ways—some from collapsing gas clouds, others from wandering black holes in dense stellar clusters, and still others from previous generations of mergers.— Sharan Banagiri, Monash University
We are no longer just looking at individual anomalies; we are seeing a true kaleidoscope of cosmic collisions.— Eric Thrane, ARC Centre of Excellence for Gravitational Wave Discovery
The Hearth Conversation Another angle on the story
Why does it matter that black holes form in multiple ways rather than one?
Because it tells us the universe is more creative than we thought. If there were only one formation channel, we'd understand black hole populations as a simple product of stellar evolution. But multiple pathways mean different histories, different ages, different compositions. It's the difference between a single recipe and a whole cookbook.
These rapidly spinning black holes—how do we know they're actually spinning that fast?
Gravitational waves carry information about the spin in their signal. When two objects orbit each other, the way spacetime ripples encodes their properties. The spin affects the shape of the orbit, the precession, the whole geometry of the merger. It's written into the wave itself.
You mentioned hierarchical mergers. Can that process repeat indefinitely?
In principle, yes. A black hole born from a merger can merge again, and again. But there are limits. Each merger adds mass and angular momentum. Eventually you reach a point where the dynamics change, where the black hole becomes so massive or spins so fast that the next collision becomes less likely. But we're seeing evidence that this process has happened at least twice in some cases.
What does the two-mass-population split actually tell us?
It's a fingerprint of formation mechanism. The lower-mass group—10 to 20 solar masses—likely comes from direct stellar collapse. The higher-mass group above 45 solar masses is harder to explain through normal stellar evolution alone. Hierarchical mergers naturally produce heavier objects. So the split suggests we're seeing two different pathways in action.
How confident are researchers in these conclusions?
Confident enough to publish, but not so confident they're claiming certainty. With nearly 400 events, the statistical power is real. But the universe could still surprise us. That's why the catalogue keeps growing. Each new detection either confirms the pattern or breaks it.