Scientists looking for dark matter have looked almost everywhere they could imagine: deep underground detectors, powerful particle colliders, precision telescopes, and maps of the universe itself. Yet, despite making up most of the matter in the cosmic realm, dark matter remained frustratingly invisible.
Now, researchers think they may have found a profoundly different way to look for it: by listening to black holes collide.
A new study published in Physical Review Letters suggests that gravitational waves—the tiny ripples in spacetime generated when black holes merge—may carry subtle fingerprints of dark matter if those black holes happen to collide within dense concentrations of the mysterious substance.
More intriguingly, when researchers applied their method to real gravitational-wave observations, one previously recorded event appeared to show a tentative preference for exactly that kind of hidden environment.
The results do not amount to a discovery of dark matter. Researchers repeatedly stress that alternative explanations are possible and that additional observations will be required. Still, the work opens a new observational front in one of modern physics’ longest-running mysteries.
“We know that dark matter is around us. It just has to be dense enough for us to see its effects,” co-author and MIT postdoc research fellow, Dr. Josu Aurrekoetxea, said in a press release. “Black holes provide a mechanism to enhance this density, which we can now search for by analyzing the gravitational waves emitted when they merge.”
Dark matter is believed to account for roughly 85 percent of all matter in the universe, yet it has never been directly detected. Scientists infer its existence because galaxies rotate too quickly and large-scale cosmic structures behave as though far more mass exists than telescopes can see.
Unlike ordinary matter, dark matter appears to interact almost exclusively through gravity, making it extraordinarily difficult to detect using conventional techniques.
That challenge motivated researchers to pose a different question. Instead of trying to see dark matter directly, could scientists detect its influence on something else?
The researchers’ answer focused on gravitational waves. These are disturbances in spacetime first directly detected in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Since then, the international LIGO–Virgo–KAGRA collaboration has cataloged dozens of black hole mergers and transformed gravitational-wave astronomy into one of the fastest-moving areas of astrophysics.
Traditionally, those signals have been treated as extraordinarily clean probes of the black holes themselves. However, in this recent study, researchers argue that the environment around merging black holes may matter more than previously thought.
The study centers on a class of hypothetical dark matter candidates called ultralight scalar particles. These represent exotic fields that appear naturally in many extensions of the Standard Model of particle physics and have long been considered viable dark matter candidates.
Under the right conditions, ultralight scalar particles could accumulate around spinning black holes, forming extremely dense clouds. Moreover, some of those clouds could become astonishingly concentrated.
According to researchers, a process called superradiance may allow rapidly spinning black holes to transfer rotational energy into surrounding ultralight particles, dramatically amplifying them.
In some scenarios, those dark matter structures could reach densities more than 30 orders of magnitude greater than the average dark matter density in our galaxy. If a pair of black holes then spiraled together inside one of these environments, the surrounding scalar field would slightly alter their orbital motion.
That change would be subtle but measurable.
Rather than producing the gravitational-wave “chirp” expected from two black holes merging in empty space, the waves would show tiny distortions in timing and phase evolution, essentially arriving with an altered rhythm.
To test the idea, researchers developed a new semi-analytic waveform model capable of predicting how black hole mergers should appear embedded within environments of scalar dark matter. They then validated those predictions using full numerical relativistic simulations that model black hole mergers inside dense scalar fields.
The simulations showed that dark matter-like scalar structures could survive the violent inspiral process better than many earlier models had suggested.
Previous thinking often assumed equal-mass black hole binaries would destroy surrounding dark matter structures before merger. However, the new simulations suggest the opposite may sometimes occur. Portions of those structures can persist and potentially leave observable signatures in gravitational waves.
Armed with their model, the researchers turned to reality.
The team analyzed 28 gravitational-wave events from the publicly available GWTC-3 catalog collected by LIGO, Virgo, and KAGRA. Most events behaved exactly as expected.
Twenty-seven appeared consistent with black holes merging in a vacuum. But one event—GW190728, detected in 2019—stood out.
When analyzed under assumptions tied to superradiance, the signal showed what researchers describe as tentative evidence for a scalar environment surrounding the merger. The statistical preference reached a Bayes factor of approximately ln(B) ≈ 3.5—enough to attract attention but well below the standard required for a discovery claim.
If that interpretation ultimately proves correct, the data would point toward an ultralight scalar particle with a mass around 10^-12 electron volts.
That would place it in an area already discussed in theoretical dark matter research, although the authors acknowledge existing black hole spin measurements create some tension with portions of that parameter space.
Importantly, the researchers emphasize that they cannot rule out more ordinary explanations.
Environmental effects, parameter indeterminacies, or constraints in current waveform models could potentially mimic some of the observed behavior. Researchers carefully examined possibilities, including orbital eccentricity and line-of-sight acceleration, and found no strong evidence that those effects explain the signal, but warn that confirmation will require future observations.
“The statistical significance of this is not high enough to claim a detection of dark matter, and further checks should be performed by independent groups,” Dr. Aurrekoetxea said. “What we think is important to highlight is that without waveform models like ours, we could be detecting black hole mergers in dark matter environments, but systematically classifying them as having occurred in vacuum.”
That said, further checks of the researcher’s theory may arrive sooner than expected.
Current gravitational-wave observatories continue collecting data, and next-generation instruments such as the Einstein Telescope and Cosmic Explorer are expected to detect mergers with far greater sensitivity and over longer durations. That improvement could make tiny environmental signatures easier to isolate from ordinary black hole physics.
For now, the result remains an intriguing hint, but not yet proof.
Nevertheless, after decades of dark matter remaining elusive through light, particles, and laboratory experiments, researchers are beginning to explore the possibility that the universe’s missing mass may announce itself in an entirely different way. Not by being seen. But by changing the sound of spacetime itself.
“We now have the potential to discover dark matter around black holes as the LVK detectors keep collecting data in the coming years,” co-author and physicist at the Center for Cosmology in Belgium, Dr. Soumen Roy, said. “It is an exciting time to search for new physics using gravitational waves.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com
Dark matter is one of the biggest mysteries of modern science, because we can’t see it, touch it or feel...
The post 10 Dark Matter Facts That Will Surprise You appeared first on Curiosmos.
Mathematicians from University College London and the University of California, Davis, have published a mathematical proof that the Universe’s accelerating expansion can be explained without dark energy, dealing a serious blow to the Lambda-cold dark matter model.
The post Is Dark Energy Unnecessary? Mathematicians Challenge Standard Cosmological Model of Universe appeared first on Sci.News: Breaking Science News.
The universe is around 14 billion years old, but scientists theorize that no stars formed for the first several hundred million years, during an era known as the cosmic dark ages. They refer to the first billion years or so after this, when stars formed, as the cosmic dawn. At that time, the very oldest galaxies first assembled from collections of gas and plasma.
As these galaxies assembled and more material became available, the number of stars formed each year increased. Around 2 to 3 billion years after the Big Bang, galaxies grew faster than they ever would, producing stars at the highest rate in the universe’s history. This era is called cosmic noon.
Researchers from the Netherlands recently investigated 3 distant galaxies whose light began its journey to Earth during cosmic noon. They selected targets from a set of ancient star-forming galaxies identified in the ALMA – Archival Large Program to Advance Kinematic Analysis or ALMA-ALPAKA project. Of these, they chose to study 3 galaxies labeled ID1, ID3, and ID13.
They combined 2 different types of data to produce a detailed description of these galaxies. First, they collected data from an enormous telescope comprising 66 antennas in Chile, known as the Atacama Large Millimeter/submillimeter Array or ALMA. They used ALMA to detect radio-wave emissions from carbon monoxide and elemental carbon in these galaxies. The researchers stated that studying these chemicals in distant galaxies could reveal how their free-floating gas clouds move. They also used publicly available data from JWST’s Near Infrared Camera, or NIRCam, to determine how much light the galaxies’ stars emitted. By analyzing cosmic noon galaxies in multiple different ways, the team aimed to measure their masses and the relative contributions of regular matter and dark matter.
They used a computer program developed by other astronomers to interpret the JWST data as a series of maps showing the distribution of stars across each galaxy. They used this light-emission data to estimate the total mass of all the stars in these galaxies. Then they developed an original computer program to map the distribution of gas through each galaxy using the ALMA data. The team used these maps to create plots, known as rotation curves, which show how fast particles orbit each galaxy’s center as a function of their distance from it.
The astronomers used these rotation curves to estimate the amount of dark matter in each galaxy. They explained that this method works because dark matter is totally invisible, but it still exerts a gravitational pull. Its gravitational pull causes visible material like stars and gas closer to the edges of these galaxies to move faster than they would in galaxies without dark matter.
The team found that these galaxies had between 39 and 80 billion times the mass of our sun, or solar masses, in stars. They had between 4 billion and nearly 16 billion solar masses worth of free-floating gas. And they had from 1 trillion to 31 trillion solar masses of dark matter.
However, when the team compared the light-emission data with the rotation curves, they found a discrepancy. Typically, dark matter resides in a shell or halo surrounding a galaxy, meaning it should mostly affect material near the galaxy’s outer edge. Since astronomers don’t usually have to account for dark matter near a galaxy’s center, they can calculate the total mass of center material based on the amount of gas and stars they see there. But near the centers of these galaxies, the team found that the masses they derived from the light emissions were less than what they calculated from the rotation curves.
They proposed multiple potential explanations for this discrepancy. First, they suggested that the halo shape might not be a good model for the dark matter distribution in all galaxies, meaning that cosmic noon galaxies could contain dark matter near their centers. Second, they suggested that stars could be packed tightly in the center of these galaxies, blocking each other’s light emissions. Third, they suggested that galaxy ID1 could have a supermassive black hole as big as 1.5% its total stellar mass at its center.
The team concluded that they now have a detailed picture of the mass distribution in these cosmic noon galaxies, but the reason for their center mass discrepancies remains elusive. They suggested that a complex relationship exists between the dark matter halos and the rest of the material within these galaxies. They indicated that future astronomers could adapt their methods to study the distribution of material in other distant galaxies studied by ALMA-ALPAKA and forthcoming galactic surveys.
The post Characterizing galaxies at “cosmic noon” appeared first on Sciworthy.
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