'Lost World' of Gravitational Waves Reveals The Origins of Black Holes
NEWS | 28 May 2026
Of all the objects in the Universe, few are as perplexing as black holes. Over the last decade, gravitational-wave observatories have revealed them in bewildering variety: giant black holes far chunkier than we thought possible, black holes rotating at dizzying speeds, and pairs so mismatched that scientists struggled to explain them. Now, with the latest release of gravitational-wave data from the LIGO-Virgo-KAGRA collaboration, astronomers finally have enough detections to move beyond individual curiosities and begin taking a true census of the black hole population. And the emerging picture suggests that the Universe has a surprisingly versatile range of black hole construction methods. "This set of nearly 400 gravitational-wave detections from LIGO and Virgo provides us with a clear indication that the binary black hole mergers we see are forming in several different ways," explains astrophysicist Sharan Banagiri of Monash University and the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) in Australia. "Some might form as one giant cloud of gas that collapses to give two massive stars that then become black holes. Others might be black holes that wander into each other in dense environments called clusters that are packed with stars. While others are the product of a previous generation of mergers between two black holes." frameborder="0″ allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen> Black holes are extremely difficult to study. They consist of matter so densely packed that their extreme gravity warps space-time around them into a region from which not even light in a vacuum is fast enough to achieve escape velocity. Since light is the main tool we use to understand the Universe, this renders black holes impenetrable to our best detection methods – but there are still some things we do know. They are thought to form from the collapsed cores of massive stars above a certain mass threshold, crushing down into an object so small, but so massive, that gravity completely overwhelms every other known force. Then, in 2015, a breakthrough in black hole science came ringing through the Universe. That was the first time humanity detected gravitational waves, the space-time ripples from a colliding pair of black holes – like waves spreading outward from a pebble dropped in a pond. Since then, our ability to detect gravitational-wave events has improved, and detections have ballooned to 390 in the newest gravitational-wave catalog – most of them from colliding black hole pairs. That's an average rate of nearly 40 detections per year. "With this catalog, we now have enough data that we can start to tease apart the properties of these black holes and to figure out where they came from," says astrophysicist Maximiliano Isi of the Simons Foundation's Flatiron Institute in the US. "We're also able to chart the expansion of the Universe over its history, which is a super important unanswered question in cosmology right now." Each gravitational-wave signal can be analyzed to infer the properties of the black holes involved. That includes the masses and spins of the two colliding black holes, and the estimated mass and spin of the larger black hole formed by the collision. The new catalog contains a number of key results, including several record-breakers. There's the clearest black hole signal detected yet, GW 250114, which allowed new tests of theoretical physics. Another signal, GW 240615dg, set the record for the best sky localization ever achieved. But these individual events pale in comparison to what the census data reveal. "We're now detecting so many of these signals that we're not just learning about individual collisions; it's the astronomical equivalent of uncovering an ancient civilization," says astrophysicist Daniel Williams of the University of Glasgow in the UK. "Today's new results are like finding a previously undiscovered hoard, revealing not just individual lives, but the structure of an entire lost world." Statistical analysis shows that black hole masses tend to cluster in two main groups: 10 solar masses and 35 solar masses. The former is probably from normal binary stars evolving together, but the latter is harder to explain with standard stellar evolution alone. However, other trends suggest that these larger objects may be "second-generation" black holes that grew in mass from a previous collision between smaller black holes. This succession of collisions is called a hierarchical merger. Since a collision can produce rapidly spinning remnants, a rapid spin that is faster than expected serves as a fingerprint for these hierarchical mergers. "One of the most fascinating things we've discovered about these new black holes is that they are spinning very fast," Banagiri says. "The Sun rotates once every 25 days. If it became a black hole and started spinning as quickly as the ones we discovered, it would be rotating several thousand times every second." And binaries that evolved together are generally expected to have similar masses – which means a collision from a wildly mismatched binary could also have involved a black hole that is the product of a prior merger. The emerging picture from the latest catalog shows this is likely the case – and it's only going to grow clearer. Related: Physicists Simulated a Black Hole in The Lab, And It Then Began to Glow The first observing run of LIGO produced three detections over four months – an average of one detection every six weeks or so. The most recent observing run bagged three to four detections per week. "We are no longer just looking at individual anomalies; instead, we are seeing a true kaleidoscope of cosmic collisions," says astrophysicist Eric Thrane of Monash University and OzGrav. "We are pushing the edges of what we know, seeing things that are more massive, spinning faster, and more unusual than ever before." The findings have been published in a preprint on the LIGO website.
Author: Michelle Starr.
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